Organelles: Specific particles of membrane-bound organized living substances present in eukaryotic cells, such as the MITOCHONDRIA; the GOLGI APPARATUS; ENDOPLASMIC RETICULUM; LYSOSOMES; PLASTIDS; and VACUOLES.Organoids: An organization of cells into an organ-like structure. Organoids can be generated in culture. They are also found in certain neoplasms.Organelle Size: The quantity of volume or surface area of ORGANELLES.Mitochondria: Semiautonomous, self-reproducing organelles that occur in the cytoplasm of all cells of most, but not all, eukaryotes. Each mitochondrion is surrounded by a double limiting membrane. The inner membrane is highly invaginated, and its projections are called cristae. Mitochondria are the sites of the reactions of oxidative phosphorylation, which result in the formation of ATP. They contain distinctive RIBOSOMES, transfer RNAs (RNA, TRANSFER); AMINO ACYL T RNA SYNTHETASES; and elongation and termination factors. Mitochondria depend upon genes within the nucleus of the cells in which they reside for many essential messenger RNAs (RNA, MESSENGER). Mitochondria are believed to have arisen from aerobic bacteria that established a symbiotic relationship with primitive protoeukaryotes. (King & Stansfield, A Dictionary of Genetics, 4th ed)Microscopy, Electron: Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen.Lysosomes: A class of morphologically heterogeneous cytoplasmic particles in animal and plant tissues characterized by their content of hydrolytic enzymes and the structure-linked latency of these enzymes. The intracellular functions of lysosomes depend on their lytic potential. The single unit membrane of the lysosome acts as a barrier between the enzymes enclosed in the lysosome and the external substrate. The activity of the enzymes contained in lysosomes is limited or nil unless the vesicle in which they are enclosed is ruptured. Such rupture is supposed to be under metabolic (hormonal) control. (From Rieger et al., Glossary of Genetics: Classical and Molecular, 5th ed)Organelle Shape: The quality of surface form or outline of ORGANELLES.Golgi Apparatus: A stack of flattened vesicles that functions in posttranslational processing and sorting of proteins, receiving them from the rough ENDOPLASMIC RETICULUM and directing them to secretory vesicles, LYSOSOMES, or the CELL MEMBRANE. The movement of proteins takes place by transfer vesicles that bud off from the rough endoplasmic reticulum or Golgi apparatus and fuse with the Golgi, lysosomes or cell membrane. (From Glick, Glossary of Biochemistry and Molecular Biology, 1990)Melanosomes: Melanin-containing organelles found in melanocytes and melanophores.Endoplasmic Reticulum: A system of cisternae in the CYTOPLASM of many cells. In places the endoplasmic reticulum is continuous with the plasma membrane (CELL MEMBRANE) or outer membrane of the nuclear envelope. If the outer surfaces of the endoplasmic reticulum membranes are coated with ribosomes, the endoplasmic reticulum is said to be rough-surfaced (ENDOPLASMIC RETICULUM, ROUGH); otherwise it is said to be smooth-surfaced (ENDOPLASMIC RETICULUM, SMOOTH). (King & Stansfield, A Dictionary of Genetics, 4th ed)Autophagy: The segregation and degradation of damaged or unwanted cytoplasmic constituents by autophagic vacuoles (cytolysosomes) composed of LYSOSOMES containing cellular components in the process of digestion; it plays an important role in BIOLOGICAL METAMORPHOSIS of amphibians, in the removal of bone by osteoclasts, and in the degradation of normal cell components in nutritional deficiency states.Vacuoles: Any spaces or cavities within a cell. They may function in digestion, storage, secretion, or excretion.Protein Transport: The process of moving proteins from one cellular compartment (including extracellular) to another by various sorting and transport mechanisms such as gated transport, protein translocation, and vesicular transport.Intracellular Membranes: Thin structures that encapsulate subcellular structures or ORGANELLES in EUKARYOTIC CELLS. They include a variety of membranes associated with the CELL NUCLEUS; the MITOCHONDRIA; the GOLGI APPARATUS; the ENDOPLASMIC RETICULUM; LYSOSOMES; PLASTIDS; and VACUOLES.Peroxisomes: Microbodies which occur in animal and plant cells and in certain fungi and protozoa. They contain peroxidase, catalase, and allied enzymes. (From Singleton and Sainsbury, Dictionary of Microbiology and Molecular Biology, 2nd ed)Microtubules: Slender, cylindrical filaments found in the cytoskeleton of plant and animal cells. They are composed of the protein TUBULIN and are influenced by TUBULIN MODULATORS.Endosomes: Cytoplasmic vesicles formed when COATED VESICLES shed their CLATHRIN coat. Endosomes internalize macromolecules bound by receptors on the cell surface.Biological Transport: The movement of materials (including biochemical substances and drugs) through a biological system at the cellular level. The transport can be across cell membranes and epithelial layers. It also can occur within intracellular compartments and extracellular compartments.Cell Fractionation: Techniques to partition various components of the cell into SUBCELLULAR FRACTIONS.Plastids: Self-replicating cytoplasmic organelles of plant and algal cells that contain pigments and may synthesize and accumulate various substances. PLASTID GENOMES are used in phylogenetic studies.Membrane Proteins: Proteins which are found in membranes including cellular and intracellular membranes. They consist of two types, peripheral and integral proteins. They include most membrane-associated enzymes, antigenic proteins, transport proteins, and drug, hormone, and lectin receptors.Kinesin: A microtubule-associated mechanical adenosine triphosphatase, that uses the energy of ATP hydrolysis to move organelles along microtubules toward the plus end of the microtubule. The protein is found in squid axoplasm, optic lobes, and in bovine brain. Bovine kinesin is a heterotetramer composed of two heavy (120 kDa) and two light (62 kDa) chains. EC 3.6.1.-.Cytoplasm: The part of a cell that contains the CYTOSOL and small structures excluding the CELL NUCLEUS; MITOCHONDRIA; and large VACUOLES. (Glick, Glossary of Biochemistry and Molecular Biology, 1990)Cytoplasmic Granules: Condensed areas of cellular material that may be bounded by a membrane.Subcellular Fractions: Components of a cell produced by various separation techniques which, though they disrupt the delicate anatomy of a cell, preserve the structure and physiology of its functioning constituents for biochemical and ultrastructural analysis. (From Alberts et al., Molecular Biology of the Cell, 2d ed, p163)Microscopy, Fluorescence: Microscopy of specimens stained with fluorescent dye (usually fluorescein isothiocyanate) or of naturally fluorescent materials, which emit light when exposed to ultraviolet or blue light. Immunofluorescence microscopy utilizes antibodies that are labeled with fluorescent dye.Phagosomes: Membrane-bound cytoplasmic vesicles formed by invagination of phagocytized material. They fuse with lysosomes to form phagolysosomes in which the hydrolytic enzymes of the lysosome digest the phagocytized material.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Chloroplasts: Plant cell inclusion bodies that contain the photosynthetic pigment CHLOROPHYLL, which is associated with the membrane of THYLAKOIDS. Chloroplasts occur in cells of leaves and young stems of plants. They are also found in some forms of PHYTOPLANKTON such as HAPTOPHYTA; DINOFLAGELLATES; DIATOMS; and CRYPTOPHYTA.Cell Compartmentation: A partitioning within cells due to the selectively permeable membranes which enclose each of the separate parts, e.g., mitochondria, lysosomes, etc.Cytoplasmic Vesicles: Membrane-limited structures derived from the plasma membrane or various intracellular membranes which function in storage, transport or metabolism.Cytoplasmic Streaming: The movement of CYTOPLASM within a CELL. It serves as an internal transport system for moving essential substances throughout the cell, and in single-celled organisms, such as the AMOEBA, it is responsible for the movement (CELL MOVEMENT) of the entire cell.Cilia: Populations of thin, motile processes found covering the surface of ciliates (CILIOPHORA) or the free surface of the cells making up ciliated EPITHELIUM. Each cilium arises from a basic granule in the superficial layer of CYTOPLASM. The movement of cilia propels ciliates through the liquid in which they live. The movement of cilia on a ciliated epithelium serves to propel a surface layer of mucus or fluid. (King & Stansfield, A Dictionary of Genetics, 4th ed)Cell Membrane: The lipid- and protein-containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells.Models, Biological: Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.Axonal Transport: The directed transport of ORGANELLES and molecules along nerve cell AXONS. Transport can be anterograde (from the cell body) or retrograde (toward the cell body). (Alberts et al., Molecular Biology of the Cell, 3d ed, pG3)Melanophores: Chromatophores (large pigment cells of fish, amphibia, reptiles and many invertebrates) which contain melanin. Short term color changes are brought about by an active redistribution of the melanophores pigment containing organelles (MELANOSOMES). Mammals do not have melanophores; however they have retained smaller pigment cells known as MELANOCYTES.Microscopy, Immunoelectron: Microscopy in which the samples are first stained immunocytochemically and then examined using an electron microscope. Immunoelectron microscopy is used extensively in diagnostic virology as part of very sensitive immunoassays.Microscopy, Electron, Transmission: Electron microscopy in which the ELECTRONS or their reaction products that pass down through the specimen are imaged below the plane of the specimen.rab GTP-Binding Proteins: A large family of MONOMERIC GTP-BINDING PROTEINS that play a key role in cellular secretory and endocytic pathways. EC 3.6.1.-.Amino Acid Sequence: The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.Endocytosis: Cellular uptake of extracellular materials within membrane-limited vacuoles or microvesicles. ENDOSOMES play a central role in endocytosis.Microtubule-Associated Proteins: High molecular weight proteins found in the MICROTUBULES of the cytoskeletal system. Under certain conditions they are required for TUBULIN assembly into the microtubules and stabilize the assembled microtubules.Dyneins: A family of multisubunit cytoskeletal motor proteins that use the energy of ATP hydrolysis to power a variety of cellular functions. Dyneins fall into two major classes based upon structural and functional criteria.Transport Vesicles: Vesicles that are involved in shuttling cargo from the interior of the cell to the cell surface, from the cell surface to the interior, across the cell or around the cell to various locations.Genome, Plastid: The genetic complement of PLASTIDS as represented in their DNA.Green Fluorescent Proteins: Protein analogs and derivatives of the Aequorea victoria green fluorescent protein that emit light (FLUORESCENCE) when excited with ULTRAVIOLET RAYS. They are used in REPORTER GENES in doing GENETIC TECHNIQUES. Numerous mutants have been made to emit other colors or be sensitive to pH.Cell Nucleus: Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (CELL NUCLEOLUS). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the ENDOPLASMIC RETICULUM. A cell may contain more than one nucleus. (From Singleton & Sainsbury, Dictionary of Microbiology and Molecular Biology, 2d ed)Microbodies: Electron-dense cytoplasmic particles bounded by a single membrane, such as PEROXISOMES; GLYOXYSOMES; and glycosomes.Mitochondrial Proteins: Proteins encoded by the mitochondrial genome or proteins encoded by the nuclear genome that are imported to and resident in the MITOCHONDRIA.Eukaryotic Cells: Cells of the higher organisms, containing a true nucleus bounded by a nuclear membrane.Myosin Type V: A subclass of myosin involved in organelle transport and membrane targeting. It is abundantly found in nervous tissue and neurosecretory cells. The heavy chains of myosin V contain unusually long neck domains that are believed to aid in translocating molecules over large distances.Protozoan Proteins: Proteins found in any species of protozoan.Microscopy, Confocal: A light microscopic technique in which only a small spot is illuminated and observed at a time. An image is constructed through point-by-point scanning of the field in this manner. Light sources may be conventional or laser, and fluorescence or transmitted observations are possible.Eukaryota: One of the three domains of life (the others being BACTERIA and ARCHAEA), also called Eukarya. These are organisms whose cells are enclosed in membranes and possess a nucleus. They comprise almost all multicellular and many unicellular organisms, and are traditionally divided into groups (sometimes called kingdoms) including ANIMALS; PLANTS; FUNGI; and various algae and other taxa that were previously part of the old kingdom Protista.Mutation: Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.Secretory Vesicles: Vesicles derived from the GOLGI APPARATUS containing material to be released at the cell surface.Saccharomyces cerevisiae: A species of the genus SACCHAROMYCES, family Saccharomycetaceae, order Saccharomycetales, known as "baker's" or "brewer's" yeast. The dried form is used as a dietary supplement.Vacuolar Proton-Translocating ATPases: Proton-translocating ATPases that are involved in acidification of a variety of intracellular compartments.Cytoskeleton: The network of filaments, tubules, and interconnecting filamentous bridges which give shape, structure, and organization to the cytoplasm.Cytosol: Intracellular fluid from the cytoplasm after removal of ORGANELLES and other insoluble cytoplasmic components.Molecular Motor Proteins: Proteins that are involved in or cause CELL MOVEMENT such as the rotary structures (flagellar motor) or the structures whose movement is directed along cytoskeletal filaments (MYOSIN; KINESIN; and DYNEIN motor families).Luminescent Proteins: Proteins which are involved in the phenomenon of light emission in living systems. Included are the "enzymatic" and "non-enzymatic" types of system with or without the presence of oxygen or co-factors.Vesicular Transport Proteins: A broad category of proteins involved in the formation, transport and dissolution of TRANSPORT VESICLES. They play a role in the intracellular transport of molecules contained within membrane vesicles. Vesicular transport proteins are distinguished from MEMBRANE TRANSPORT PROTEINS, which move molecules across membranes, by the mode in which the molecules are transported.Flagella: A whiplike motility appendage present on the surface cells. Prokaryote flagella are composed of a protein called FLAGELLIN. Bacteria can have a single flagellum, a tuft at one pole, or multiple flagella covering the entire surface. In eukaryotes, flagella are threadlike protoplasmic extensions used to propel flagellates and sperm. Flagella have the same basic structure as CILIA but are longer in proportion to the cell bearing them and present in much smaller numbers. (From King & Stansfield, A Dictionary of Genetics, 4th ed)Cells, Cultured: Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.Recombinant Fusion Proteins: Recombinant proteins produced by the GENETIC TRANSLATION of fused genes formed by the combination of NUCLEIC ACID REGULATORY SEQUENCES of one or more genes with the protein coding sequences of one or more genes.Chlorophyta: A phylum of photosynthetic EUKARYOTA bearing double membrane-bound plastids containing chlorophyll a and b. They comprise the classical green algae, and represent over 7000 species that live in a variety of primarily aquatic habitats. Only about ten percent are marine species, most live in freshwater.Mitochondrial Membranes: The two lipoprotein layers in the MITOCHONDRION. The outer membrane encloses the entire mitochondrion and contains channels with TRANSPORT PROTEINS to move molecules and ions in and out of the organelle. The inner membrane folds into cristae and contains many ENZYMES important to cell METABOLISM and energy production (MITOCHONDRIAL ATP SYNTHASE).Cellular Structures: Components of a cell.Cell Line: Established cell cultures that have the potential to propagate indefinitely.Lysosome-Associated Membrane Glycoproteins: Ubiquitously expressed integral membrane glycoproteins found in the LYSOSOME.Blastocystis: A genus of protozoa of the suborder BLASTOCYSTINA. It was first classified as a yeast but further studies have shown it to be a protozoan.Membrane Fusion: The adherence and merging of cell membranes, intracellular membranes, or artificial membranes to each other or to viruses, parasites, or interstitial particles through a variety of chemical and physical processes.Secretory Pathway: A series of sequential intracellular steps involved in the transport of proteins (such as hormones and enzymes) from the site of synthesis to outside the cell. The pathway involves membrane-bound compartments through which the newly synthesized proteins undergo POST-TRANSLATIONAL MODIFICATIONS, packaging, storage, or transportation to the PLASMA MEMBRANE for secretion.Fluorescent Antibody Technique: Test for tissue antigen using either a direct method, by conjugation of antibody with fluorescent dye (FLUORESCENT ANTIBODY TECHNIQUE, DIRECT) or an indirect method, by formation of antigen-antibody complex which is then labeled with fluorescein-conjugated anti-immunoglobulin antibody (FLUORESCENT ANTIBODY TECHNIQUE, INDIRECT). The tissue is then examined by fluorescence microscopy.Mitochondrial Dynamics: The continuous remodeling of MITOCHONDRIA shape by fission and fusion in response to physiological conditions.Genome, Mitochondrial: The genetic complement of MITOCHONDRIA as represented in their DNA.Carrier Proteins: Transport proteins that carry specific substances in the blood or across cell membranes.Saccharomyces cerevisiae Proteins: Proteins obtained from the species SACCHAROMYCES CEREVISIAE. The function of specific proteins from this organism are the subject of intense scientific interest and have been used to derive basic understanding of the functioning similar proteins in higher eukaryotes.Brefeldin A: A fungal metabolite which is a macrocyclic lactone exhibiting a wide range of antibiotic activity.Inclusion Bodies: A generic term for any circumscribed mass of foreign (e.g., lead or viruses) or metabolically inactive materials (e.g., ceroid or MALLORY BODIES), within the cytoplasm or nucleus of a cell. Inclusion bodies are in cells infected with certain filtrable viruses, observed especially in nerve, epithelial, or endothelial cells. (Stedman, 25th ed)DNA, Mitochondrial: Double-stranded DNA of MITOCHONDRIA. In eukaryotes, the mitochondrial GENOME is circular and codes for ribosomal RNAs, transfer RNAs, and about 10 proteins.Weibel-Palade Bodies: Rod-shaped storage granules for VON WILLEBRAND FACTOR specific to endothelial cells.Calcium: A basic element found in nearly all organized tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes.Arabidopsis: A plant genus of the family BRASSICACEAE that contains ARABIDOPSIS PROTEINS and MADS DOMAIN PROTEINS. The species A. thaliana is used for experiments in classical plant genetics as well as molecular genetic studies in plant physiology, biochemistry, and development.Adaptor Protein Complex 3: An adaptor protein complex found primarily on perinuclear compartments.Plants: Multicellular, eukaryotic life forms of kingdom Plantae (sensu lato), comprising the VIRIDIPLANTAE; RHODOPHYTA; and GLAUCOPHYTA; all of which acquired chloroplasts by direct endosymbiosis of CYANOBACTERIA. They are characterized by a mainly photosynthetic mode of nutrition; essentially unlimited growth at localized regions of cell divisions (MERISTEMS); cellulose within cells providing rigidity; the absence of organs of locomotion; absence of nervous and sensory systems; and an alternation of haploid and diploid generations.Endoplasmic Reticulum, Smooth: A type of endoplasmic reticulum lacking associated ribosomes on the membrane surface. It exhibits a wide range of specialized metabolic functions including supplying enzymes for steroid synthesis, detoxification, and glycogen breakdown. In muscle cells, smooth endoplasmic reticulum is called SARCOPLASMIC RETICULUM.Centrifugation, Density Gradient: Separation of particles according to density by employing a gradient of varying densities. At equilibrium each particle settles in the gradient at a point equal to its density. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Cell Biology: The study of the structure, behavior, growth, reproduction, and pathology of cells; and the function and chemistry of cellular components.Adenosine Triphosphate: An adenine nucleotide containing three phosphate groups esterified to the sugar moiety. In addition to its crucial roles in metabolism adenosine triphosphate is a neurotransmitter.Exocytosis: Cellular release of material within membrane-limited vesicles by fusion of the vesicles with the CELL MEMBRANE.Axons: Nerve fibers that are capable of rapidly conducting impulses away from the neuron cell body.Proteins: Linear POLYPEPTIDES that are synthesized on RIBOSOMES and may be further modified, crosslinked, cleaved, or assembled into complex proteins with several subunits. The specific sequence of AMINO ACIDS determines the shape the polypeptide will take, during PROTEIN FOLDING, and the function of the protein.Actin Cytoskeleton: Fibers composed of MICROFILAMENT PROTEINS, which are predominately ACTIN. They are the smallest of the cytoskeletal filaments.Magnetosomes: Membrane-bound prokaryotic organelles of magnetotactic bacteria that contain chains of MAGNETITE crystals which orient the bacteria to geomagnetic fields.HeLa Cells: The first continuously cultured human malignant CELL LINE, derived from the cervical carcinoma of Henrietta Lacks. These cells are used for VIRUS CULTIVATION and antitumor drug screening assays.Fluorescent Dyes: Agents that emit light after excitation by light. The wave length of the emitted light is usually longer than that of the incident light. Fluorochromes are substances that cause fluorescence in other substances, i.e., dyes used to mark or label other compounds with fluorescent tags.Hydrogen-Ion Concentration: The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH = log 1/2[1/(H+)], where (H+) is the hydrogen ion concentration in gram equivalents per liter of solution. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Plant Proteins: Proteins found in plants (flowers, herbs, shrubs, trees, etc.). The concept does not include proteins found in vegetables for which VEGETABLE PROTEINS is available.Histocytochemistry: Study of intracellular distribution of chemicals, reaction sites, enzymes, etc., by means of staining reactions, radioactive isotope uptake, selective metal distribution in electron microscopy, or other methods.Protein Binding: The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments.Actins: Filamentous proteins that are the main constituent of the thin filaments of muscle fibers. The filaments (known also as filamentous or F-actin) can be dissociated into their globular subunits; each subunit is composed of a single polypeptide 375 amino acids long. This is known as globular or G-actin. In conjunction with MYOSINS, actin is responsible for the contraction and relaxation of muscle.Sequence Homology, Amino Acid: The degree of similarity between sequences of amino acids. This information is useful for the analyzing genetic relatedness of proteins and species.Decapodiformes: A superorder of CEPHALOPODS comprised of squid, cuttlefish, and their relatives. Their distinguishing feature is the modification of their fourth pair of arms into tentacles, resulting in 10 limbs.Phylogeny: The relationships of groups of organisms as reflected by their genetic makeup.Signal Transduction: The intracellular transfer of information (biological activation/inhibition) through a signal pathway. In each signal transduction system, an activation/inhibition signal from a biologically active molecule (hormone, neurotransmitter) is mediated via the coupling of a receptor/enzyme to a second messenger system or to an ion channel. Signal transduction plays an important role in activating cellular functions, cell differentiation, and cell proliferation. Examples of signal transduction systems are the GAMMA-AMINOBUTYRIC ACID-postsynaptic receptor-calcium ion channel system, the receptor-mediated T-cell activation pathway, and the receptor-mediated activation of phospholipases. Those coupled to membrane depolarization or intracellular release of calcium include the receptor-mediated activation of cytotoxic functions in granulocytes and the synaptic potentiation of protein kinase activation. Some signal transduction pathways may be part of larger signal transduction pathways; for example, protein kinase activation is part of the platelet activation signal pathway.trans-Golgi Network: A network of membrane compartments, located at the cytoplasmic side of the GOLGI APPARATUS, where proteins and lipids are sorted for transport to various locations in the cell or cell membrane.Electron Microscope Tomography: A tomographic technique for obtaining 3-dimensional images with transmission electron microscopy.Centrioles: Self-replicating, short, fibrous, rod-shaped organelles. Each centriole is a short cylinder containing nine pairs of peripheral microtubules, arranged so as to form the wall of the cylinder.Apicomplexa: A phylum of unicellular parasitic EUKARYOTES characterized by the presence of complex apical organelles generally consisting of a conoid that aids in penetrating host cells, rhoptries that possibly secrete a proteolytic enzyme, and subpellicular microtubules that may be related to motility.Potassium Iodide: An inorganic compound that is used as a source of iodine in thyrotoxic crisis and in the preparation of thyrotoxic patients for thyroidectomy. (From Dorland, 27th ed)Toxoplasma: A genus of protozoa parasitic to birds and mammals. T. gondii is one of the most common infectious pathogenic animal parasites of man.Propylene Glycol: A clear, colorless, viscous organic solvent and diluent used in pharmaceutical preparations.Lipid Metabolism: Physiological processes in biosynthesis (anabolism) and degradation (catabolism) of LIPIDS.Mitochondrial Degradation: Proteolytic breakdown of the MITOCHONDRIA.Arabidopsis Proteins: Proteins that originate from plants species belonging to the genus ARABIDOPSIS. The most intensely studied species of Arabidopsis, Arabidopsis thaliana, is commonly used in laboratory experiments.Base Sequence: The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.Protein Structure, Tertiary: The level of protein structure in which combinations of secondary protein structures (alpha helices, beta sheets, loop regions, and motifs) pack together to form folded shapes called domains. Disulfide bridges between cysteines in two different parts of the polypeptide chain along with other interactions between the chains play a role in the formation and stabilization of tertiary structure. Small proteins usually consist of only one domain but larger proteins may contain a number of domains connected by segments of polypeptide chain which lack regular secondary structure.Acridine Orange: A cationic cytochemical stain specific for cell nuclei, especially DNA. It is used as a supravital stain and in fluorescence cytochemistry. It may cause mutations in microorganisms.Plant Cells: Basic functional unit of plants.Proteomics: The systematic study of the complete complement of proteins (PROTEOME) of organisms.Multivesicular Bodies: Endosomes containing intraluminal vesicles which are formed by the inward budding of the endosome membrane. Multivesicular bodies (MVBs) may fuse with other organelles such as LYSOSOMES or fuse back with the PLASMA MEMBRANE releasing their contents by EXOCYTOSIS. The MVB intraluminal vesicles released into the extracellular environment are known as EXOSOMES.Sequence Alignment: The arrangement of two or more amino acid or base sequences from an organism or organisms in such a way as to align areas of the sequences sharing common properties. The degree of relatedness or homology between the sequences is predicted computationally or statistically based on weights assigned to the elements aligned between the sequences. This in turn can serve as a potential indicator of the genetic relatedness between the organisms.Protein Sorting Signals: Amino acid sequences found in transported proteins that selectively guide the distribution of the proteins to specific cellular compartments.Melanocytes: Mammalian pigment cells that produce MELANINS, pigments found mainly in the EPIDERMIS, but also in the eyes and the hair, by a process called melanogenesis. Coloration can be altered by the number of melanocytes or the amount of pigment produced and stored in the organelles called MELANOSOMES. The large non-mammalian melanin-containing cells are called MELANOPHORES.Acid Phosphatase: An enzyme that catalyzes the conversion of an orthophosphoric monoester and water to an alcohol and orthophosphate. EC, Liver: Mitochondria in hepatocytes. As in all mitochondria, there are an outer membrane and an inner membrane, together creating two separate mitochondrial compartments: the internal matrix space and a much narrower intermembrane space. In the liver mitochondrion, an estimated 67% of the total mitochondrial proteins is located in the matrix. (From Alberts et al., Molecular Biology of the Cell, 2d ed, p343-4)Nocodazole: Nocodazole is an antineoplastic agent which exerts its effect by depolymerizing microtubules.Magnetospirillum: A genus of microaerophilic, gram-negative bacteria that forms crystals of the mineral magnetite in special organelles called MAGNETOSOMES.GTP Phosphohydrolases: Enzymes that hydrolyze GTP to GDP. EC 3.6.1.-.Tubulin: A microtubule subunit protein found in large quantities in mammalian brain. It has also been isolated from SPERM FLAGELLUM; CILIA; and other sources. Structurally, the protein is a dimer with a molecular weight of approximately 120,000 and a sedimentation coefficient of 5.8S. It binds to COLCHICINE; VINCRISTINE; and VINBLASTINE.Ciliophora: A phylum of EUKARYOTES characterized by the presence of cilia at some time during the life cycle. It comprises three classes: KINETOFRAGMINOPHOREA; OLIGOHYMENOPHOREA; and POLYMENOPHOREA.Trypanosoma brucei brucei: A hemoflagellate subspecies of parasitic protozoa that causes nagana in domestic and game animals in Africa. It apparently does not infect humans. It is transmitted by bites of tsetse flies (Glossina).Adenosine Triphosphatases: A group of enzymes which catalyze the hydrolysis of ATP. The hydrolysis reaction is usually coupled with another function such as transporting Ca(2+) across a membrane. These enzymes may be dependent on Ca(2+), Mg(2+), anions, H+, or DNA.Rhodophyta: Plants of the division Rhodophyta, commonly known as red algae, in which the red pigment (PHYCOERYTHRIN) predominates. However, if this pigment is destroyed, the algae can appear purple, brown, green, or yellow. Two important substances found in the cell walls of red algae are AGAR and CARRAGEENAN. Some rhodophyta are notable SEAWEED (macroalgae).Movement: The act, process, or result of passing from one place or position to another. It differs from LOCOMOTION in that locomotion is restricted to the passing of the whole body from one place to another, while movement encompasses both locomotion but also a change of the position of the whole body or any of its parts. Movement may be used with reference to humans, vertebrate and invertebrate animals, and microorganisms. Differentiate also from MOTOR ACTIVITY, movement associated with behavior.Liver: A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances.Chediak-Higashi Syndrome: A form of phagocyte bactericidal dysfunction characterized by unusual oculocutaneous albinism, high incidence of lymphoreticular neoplasms, and recurrent pyogenic infections. In many cell types, abnormal lysosomes are present leading to defective pigment distribution and abnormal neutrophil functions. The disease is transmitted by autosomal recessive inheritance and a similar disorder occurs in the beige mouse, the Aleutian mink, and albino Hereford cattle.Kinetics: The rate dynamics in chemical or physical systems.Immunoblotting: Immunologic method used for detecting or quantifying immunoreactive substances. The substance is identified by first immobilizing it by blotting onto a membrane and then tagging it with labeled antibodies.DNA, Chloroplast: Deoxyribonucleic acid that makes up the genetic material of CHLOROPLASTS.Microscopy, Electron, Scanning: Microscopy in which the object is examined directly by an electron beam scanning the specimen point-by-point. The image is constructed by detecting the products of specimen interactions that are projected above the plane of the sample, such as backscattered electrons. Although SCANNING TRANSMISSION ELECTRON MICROSCOPY also scans the specimen point by point with the electron beam, the image is constructed by detecting the electrons, or their interaction products that are transmitted through the sample plane, so that is a form of TRANSMISSION ELECTRON MICROSCOPY.Centrifugation: Process of using a rotating machine to generate centrifugal force to separate substances of different densities, remove moisture, or simulate gravitational effects. It employs a large motor-driven apparatus with a long arm, at the end of which human and animal subjects, biological specimens, or equipment can be revolved and rotated at various speeds to study gravitational effects. (From Websters, 10th ed; McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Microscopy, Video: Microscopy in which television cameras are used to brighten magnified images that are otherwise too dark to be seen with the naked eye. It is used frequently in TELEPATHOLOGY.Neurons: The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the NERVOUS SYSTEM.Biological Transport, Active: The movement of materials across cell membranes and epithelial layers against an electrochemical gradient, requiring the expenditure of metabolic energy.Cloning, Molecular: The insertion of recombinant DNA molecules from prokaryotic and/or eukaryotic sources into a replicating vehicle, such as a plasmid or virus vector, and the introduction of the resultant hybrid molecules into recipient cells without altering the viability of those cells.Microscopy, Phase-Contrast: A form of interference microscopy in which variations of the refracting index in the object are converted into variations of intensity in the image. This is achieved by the action of a phase plate.Cytochalasins: 11- to 14-membered macrocyclic lactones with a fused isoindolone. Members with INDOLES attached at the C10 position are called chaetoglobosins. They are produced by various fungi. Some members interact with ACTIN and inhibit CYTOKINESIS.Proteome: The protein complement of an organism coded for by its genome.Proton Pumps: Integral membrane proteins that transport protons across a membrane. This transport can be linked to the hydrolysis of ADENOSINE TRIPHOSPHATE. What is referred to as proton pump inhibitors frequently is about POTASSIUM HYDROGEN ATPASE.Synaptic Vesicles: Membrane-bound compartments which contain transmitter molecules. Synaptic vesicles are concentrated at presynaptic terminals. They actively sequester transmitter molecules from the cytoplasm. In at least some synapses, transmitter release occurs by fusion of these vesicles with the presynaptic membrane, followed by exocytosis of their contents.Fungal Proteins: Proteins found in any species of fungus.Propanediol Dehydratase: An enzyme that catalyzes the dehydration of 1,2-propanediol to propionaldehyde. EC, Algal: Deoxyribonucleic acid that makes up the genetic material of algae.Bacterial Proteins: Proteins found in any species of bacterium.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Macrolides: A group of often glycosylated macrocyclic compounds formed by chain extension of multiple PROPIONATES cyclized into a large (typically 12, 14, or 16)-membered lactone. Macrolides belong to the POLYKETIDES class of natural products, and many members exhibit ANTIBIOTIC properties.Microscopy: The use of instrumentation and techniques for visualizing material and details that cannot be seen by the unaided eye. It is usually done by enlarging images, transmitted by light or electron beams, with optical or magnetic lenses that magnify the entire image field. With scanning microscopy, images are generated by collecting output from the specimen in a point-by-point fashion, on a magnified scale, as it is scanned by a narrow beam of light or electrons, a laser, a conductive probe, or a topographical probe.Centrosome: The cell center, consisting of a pair of CENTRIOLES surrounded by a cloud of amorphous material called the pericentriolar region. During interphase, the centrosome nucleates microtubule outgrowth. The centrosome duplicates and, during mitosis, separates to form the two poles of the mitotic spindle (MITOTIC SPINDLE APPARATUS).Blotting, Western: Identification of proteins or peptides that have been electrophoretically separated by blot transferring from the electrophoresis gel to strips of nitrocellulose paper, followed by labeling with antibody probes.Mycoplasma pneumoniae: Short filamentous organism of the genus Mycoplasma, which binds firmly to the cells of the respiratory epithelium. It is one of the etiologic agents of non-viral primary atypical pneumonia in man.Protein Processing, Post-Translational: Any of various enzymatically catalyzed post-translational modifications of PEPTIDES or PROTEINS in the cell of origin. These modifications include carboxylation; HYDROXYLATION; ACETYLATION; PHOSPHORYLATION; METHYLATION; GLYCOSYLATION; ubiquitination; oxidation; proteolysis; and crosslinking and result in changes in molecular weight and electrophoretic motility.Homeostasis: The processes whereby the internal environment of an organism tends to remain balanced and stable.Synaptophysin: A MARVEL domain-containing protein found in the presynaptic vesicles of NEURONS and NEUROENDOCRINE CELLS. It is commonly used as an immunocytochemical marker for neuroendocrine differentiation.Phenotype: The outward appearance of the individual. It is the product of interactions between genes, and between the GENOTYPE and the environment.Cercozoa: A group of amoeboid and flagellate EUKARYOTES in the supergroup RHIZARIA. They feed by means of threadlike pseudopods.Evolution, Molecular: The process of cumulative change at the level of DNA; RNA; and PROTEINS, over successive generations.Immunohistochemistry: Histochemical localization of immunoreactive substances using labeled antibodies as reagents.Endoplasmic Reticulum, Rough: A type of endoplasmic reticulum (ER) where polyribosomes are present on the cytoplasmic surfaces of the ER membranes. This form of ER is prominent in cells specialized for protein secretion and its principal function is to segregate proteins destined for export or intracellular utilization.Staining and Labeling: The marking of biological material with a dye or other reagent for the purpose of identifying and quantitating components of tissues, cells or their extracts.Time-Lapse Imaging: Recording serial images of a process at regular intervals spaced out over a longer period of time than the time in which the recordings will be played back.Mesophyll Cells: Large and highly vacuolated cells possessing many chloroplasts occuring in the interior cross-section of leaves, juxtaposed between the epidermal layers.3,3'-Diaminobenzidine

Association of snRNA genes with coiled bodies is mediated by nascent snRNA transcripts. (1/2526)

BACKGROUND: Coiled bodies are nuclear organelles that are highly enriched in small nuclear ribonucleoproteins (snRNPs) and certain basal transcription factors. Surprisingly, coiled bodies not only contain mature U snRNPs but also associate with specific chromosomal loci, including gene clusters that encode U snRNAs and histone messenger RNAs. The mechanism(s) by which coiled bodies associate with these genes is completely unknown. RESULTS: Using stable cell lines, we show that artificial tandem arrays of human U1 and U2 snRNA genes colocalize with coiled bodies and that the frequency of the colocalization depends directly on the transcriptional activity of the array. Association of the genes with coiled bodies was abolished when the artificial U2 arrays contained promoter mutations that prevent transcription or when RNA polymerase II transcription was globally inhibited by alpha-amanitin. Remarkably, the association was also abolished when the U2 snRNA coding regions were replaced by heterologous sequences. CONCLUSIONS: The requirement for the U2 snRNA coding region indicates that association of snRNA genes with coiled bodies is mediated by the nascent U2 RNA itself, not by DNA or DNA-bound proteins. Our data provide the first evidence that association of genes with a nuclear organelle can be directed by an RNA and suggest an autogenous feedback regulation model.  (+info)

Hsp60 is targeted to a cryptic mitochondrion-derived organelle ("crypton") in the microaerophilic protozoan parasite Entamoeba histolytica. (2/2526)

Entamoeba histolytica is a microaerophilic protozoan parasite in which neither mitochondria nor mitochondrion-derived organelles have been previously observed. Recently, a segment of an E. histolytica gene was identified that encoded a protein similar to the mitochondrial 60-kDa heat shock protein (Hsp60 or chaperonin 60), which refolds nuclear-encoded proteins after passage through organellar membranes. The possible function and localization of the amebic Hsp60 were explored here. Like Hsp60 of mitochondria, amebic Hsp60 RNA and protein were both strongly induced by incubating parasites at 42 degreesC. 5' and 3' rapid amplifications of cDNA ends were used to obtain the entire E. histolytica hsp60 coding region, which predicted a 536-amino-acid Hsp60. The E. histolytica hsp60 gene protected from heat shock Escherichia coli groEL mutants, demonstrating the chaperonin function of the amebic Hsp60. The E. histolytica Hsp60, which lacked characteristic carboxy-terminal Gly-Met repeats, had a 21-amino-acid amino-terminal, organelle-targeting presequence that was cleaved in vivo. This presequence was necessary to target Hsp60 to one (and occasionally two or three) short, cylindrical organelle(s). In contrast, amebic alcohol dehydrogenase 1 and ferredoxin, which are bacteria-like enzymes, were diffusely distributed throughout the cytosol. We suggest that the Hsp60-associated, mitochondrion-derived organelle identified here be named "crypton," as its structure was previously hidden and its function is still cryptic.  (+info)

A novel interaction mechanism accounting for different acylphosphatase effects on cardiac and fast twitch skeletal muscle sarcoplasmic reticulum calcium pumps. (3/2526)

In cardiac and skeletal muscle Ca2+ translocation from cytoplasm into sarcoplasmic reticulum (SR) is accomplished by different Ca2+-ATPases whose functioning involves the formation and decomposition of an acylphosphorylated phosphoenzyme intermediate (EP). In this study we found that acylphosphatase, an enzyme well represented in muscular tissues and which actively hydrolyzes EP, had different effects on heart (SERCA2a) and fast twitch skeletal muscle SR Ca2+-ATPase (SERCA1). With physiological acylphosphatase concentrations SERCA2a exhibited a parallel increase in the rates of both ATP hydrolysis and Ca2+ transport; in contrast, SERCA1 appeared to be uncoupled since the stimulation of ATP hydrolysis matched an inhibition of Ca2+ pump. These different effects probably depend on phospholamban, which is associated with SERCA2a but not SERCA1. Consistent with this view, the present study suggests that acylphosphatase-induced stimulation of SERCA2a, in addition to an enhanced EP hydrolysis, may be due to a displacement of phospholamban, thus to a removal of its inhibitory effect.  (+info)

Rational analyses of organelle trajectories in tobacco pollen tubes reveal characteristics of the actomyosin cytoskeleton. (4/2526)

To gain insight into the characteristics of organelle movement and the underlying actomyosin motility system in tobacco pollen tubes, we collected data points representing sequential organelle positions in control and cytochalasin-treated cells, and in a sample of extruded cytoplasm. These data were utilized to reconstruct approximately 900 tracks, representing individual organelle movements, and to produce a quantitative analysis of the movement properties, supported by statistical tests. Each reconstructed track appeared to be unique and to show irregularities in velocity and direction of movement. The regularity quotient was near 2 at the tip and above 3 elsewhere in the cell, indicating that movement is more vectorial in the tube area. Similarly, the progressiveness ratio showed that there were relatively more straight trajectories in the tube region than at the tip. Consistent with these data, arithmetical dissection revealed a high degree of randomlike movement in the apex, lanes with tip-directed movement along the flanks, and grain-directed movement in the center of the tube. Intercalated lanes with bidirectional movement had lower organelle velocity, suggesting that steric hindrance plays a role. The results from the movement analysis indicate that the axial arrangement of the actin filaments and performance of the actomyosin system increases from tip to base, and that the opposite polarity of the actin filaments in the peripheral (+-ends of acting filaments toward the tip) versus the central cytoplasm (+-ends of actin filaments toward to the grain) is installed within a few minutes in these tip-growing cells.  (+info)

Redundant systems of phosphatidic acid biosynthesis via acylation of glycerol-3-phosphate or dihydroxyacetone phosphate in the yeast Saccharomyces cerevisiae. (5/2526)

In the yeast Saccharomyces cerevisiae lipid particles harbor two acyltransferases, Gat1p and Slc1p, which catalyze subsequent steps of acylation required for the formation of phosphatidic acid. Both enzymes are also components of the endoplasmic reticulum, but this compartment contains additional acyltransferase(s) involved in the biosynthesis of phosphatidic acid (K. Athenstaedt and G. Daum, J. Bacteriol. 179:7611-7616, 1997). Using the gat1 mutant strain TTA1, we show here that Gat1p present in both subcellular fractions accepts glycerol-3-phosphate and dihydroxyacetone phosphate as a substrate. Similarly, the additional acyltransferase(s) present in the endoplasmic reticulum can acylate both precursors. In contrast, yeast mitochondria harbor an enzyme(s) that significantly prefers dihydroxyacetone phosphate as a substrate for acylation, suggesting that at least one additional independent acyltransferase is present in this organelle. Surprisingly, enzymatic activity of 1-acyldihydroxyacetone phosphate reductase, which is required for the conversion of 1-acyldihydroxyacetone phosphate to 1-acylglycerol-3-phosphate (lysophosphatidic acid), is detectable only in lipid particles and the endoplasmic reticulum and not in mitochondria. In vivo labeling of wild-type cells with [2-3H, U-14C]glycerol revealed that both glycerol-3-phosphate and dihydroxyacetone phosphate can be incorporated as a backbone of glycerolipids. In the gat1 mutant and the 1-acylglycerol-3-phosphate acyltransferase slc1 mutant, the dihydroxyacetone phosphate pathway of phosphatidic acid biosynthesis is slightly preferred as compared to the wild type. Thus, mutations of the major acyltransferases Gat1p and Slc1p lead to an increased contribution of mitochondrial acyltransferase(s) to glycerolipid synthesis due to their substrate preference for dihydroxyacetone phosphate.  (+info)

Surface proteins of gram-positive bacteria and mechanisms of their targeting to the cell wall envelope. (6/2526)

The cell wall envelope of gram-positive bacteria is a macromolecular, exoskeletal organelle that is assembled and turned over at designated sites. The cell wall also functions as a surface organelle that allows gram-positive pathogens to interact with their environment, in particular the tissues of the infected host. All of these functions require that surface proteins and enzymes be properly targeted to the cell wall envelope. Two basic mechanisms, cell wall sorting and targeting, have been identified. Cell well sorting is the covalent attachment of surface proteins to the peptidoglycan via a C-terminal sorting signal that contains a consensus LPXTG sequence. More than 100 proteins that possess cell wall-sorting signals, including the M proteins of Streptococcus pyogenes, protein A of Staphylococcus aureus, and several internalins of Listeria monocytogenes, have been identified. Cell wall targeting involves the noncovalent attachment of proteins to the cell surface via specialized binding domains. Several of these wall-binding domains appear to interact with secondary wall polymers that are associated with the peptidoglycan, for example teichoic acids and polysaccharides. Proteins that are targeted to the cell surface include muralytic enzymes such as autolysins, lysostaphin, and phage lytic enzymes. Other examples for targeted proteins are the surface S-layer proteins of bacilli and clostridia, as well as virulence factors required for the pathogenesis of L. monocytogenes (internalin B) and Streptococcus pneumoniae (PspA) infections. In this review we describe the mechanisms for both sorting and targeting of proteins to the envelope of gram-positive bacteria and review the functions of known surface proteins.  (+info)

Rat liver GTP-binding proteins mediate changes in mitochondrial membrane potential and organelle fusion. (7/2526)

The variety of mitochondrial morphology in healthy and diseased cells can be explained by regulated mitochondrial fusion. Previously, a mitochondrial outer membrane fraction containing fusogenic, aluminum fluoride (AlF4)-sensitive GTP-binding proteins (mtg) was separated from rat liver (J. D. Cortese, Exp. Cell Res. 240: 122-133, 1998). Quantitative confocal microscopy now reveals that mtg transiently increases mitochondrial membrane potential (DeltaPsi) when added to permeabilized rat hepatocytes (15%), rat fibroblasts (19%), and rabbit myocytes (10%). This large mtg-induced DeltaPsi increment is blocked by fusogenic GTPase-specific modulators such as guanosine 5'-O-(3-thiotriphosphate), excess GTP (>100 microM), and AlF4, suggesting a linkage between DeltaPsi and mitochondrial fusion. Accordingly, stereometric analysis shows that decreasing DeltaPsi or ATP synthesis with respiratory inhibitors limits mtg- and AlF4-induced mitochondrial fusion. Also, a specific G protein inhibitor (Bordetella pertussis toxin) hyperpolarizes mitochondria and leads to a loss of AlF4-dependent mitochondrial fusion. These results place mtg-induced DeltaPsi changes upstream of AlF4-induced mitochondrial fusion, suggesting that GTPases exert DeltaPsi-dependent control of the fusion process. Mammalian mitochondrial morphology thus can be modulated by cellular energetics.  (+info)

Occurrence of prostasome-like membrane vesicles in equine seminal plasma. (8/2526)

Equine seminal plasma was shown to contain membrane vesicles that are similar to the well characterized prostasomes in human seminal plasma. Determination of nucleoside and nucleotide concentrations of these particles have shown that ATP, ADP and adenosine are the main components of the nucleotidic pool. 5' nucleotidase, endopeptidase and dipeptidyl peptidase i.v. activities have been found on the surface of the particles. The interaction between these prostasome-like vesicles and spermatozoa was demonstrated by electron micrograph scans which revealed the steps of a fusion-like process leading to mixing of the membranes. In addition, endopeptidase activity, a marker enzyme of these seminal vesicles that is normally absent from equine spermatozoa, was shown to be acquired by these cells after interaction with the vesicles. The addition of these vesicles to equine spermatozoa resulted in the modification of adenylate catabolism. Therefore, a role in stabilizing the energy charge of the spermatozoa thus allowing longer viability is proposed for these organelles.  (+info)

  • Biomedical engineers at Duke University have demonstrated a method for controlling the phase separation of an emerging class of proteins to create artificial membrane-less organelles within human cells. (
  • In this organelle, proteins undergo modifications and folding to yield the final, functional protein structures. (
  • The mass-spectrometry-based identification of proteins has created opportunities for the study of organelles, transport intermediates and large subcellular structures. (
  • Organelles are tiny structures that perform very specific functions within cells, such as producing energy or manufacturing proteins. (
  • An organelle called the Golgi complex then moves the enzymes-and other proteins-into the membranes and distributes them. (
  • Moreover, the ATPases not only ensure the self-organised formation of organelles, but also use ATP-dependent binding of RNA to regulate the transport of RNA molecules and proteins into these structures, where the RNA molecules are collected. (
  • 1. What are the fluorescent proteins used for the organelle markers? (
  • Upon starvation cells undergo autophagy, a cellular degradation pathway important in the turnover of whole organelles and long lived proteins. (
  • Cluster analysis of the recorded protein profiles revealed that cytosolic proteins were degraded rapidly, whereas proteins annotated to various complexes and organelles were degraded later at different time periods. (
  • Autophagy is responsible for cytoplasmic bulk degradation and thought to be important for the turnover of whole organelles and long lived proteins ( 8 , 9 ). (
  • Establishing and maintaining order requires mechanisms to synthesize and localize proteins to specific organelles, and monitor and regulate individual organelles. (
  • To create these distinctions, neurons must differentially target both proteins and organelles to these cellular compartments, but how this is achieved remains poorly understood. (
  • Furthermore, they extend the concept of an AIS to include not only localizing of proteins, but also regulating the compartment restriction of organelles through characterization of unc-16 mutants that disrupt somatodendritic vs . axon targeting of organelles. (
  • Conclusion] The Zera sequence provides an efficient and universal means to produce recombinant proteins by accumulation in ER-derived organelles. (
  • I have searched for images of endothelial cells showing the various organelles that they contain in order to confirm the above statement: Although endothelial cells contain all the basic cell machinery, there tend to be fewer of each type of organelle than in some other tissues, because they have relatively small amounts of cytoplasm. (
  • The cytoplasm is relatively simple with few organelles, mostly concentrated in the perinuclear zone. (
  • all organelles are contained in the cytoplasm. (
  • The cytoplasm is the fluid that holds all of the organelles in place. (
  • The method disclosed comprises isolation and concentration of the organelle to be transferred from the tissue of the donor followed by injection of the organelle into the cytoplasm of a target organism, whereupon the transgene of the injected organelle is expressed. (
  • These protein-based liquid globules, called membraneless organelles, selectively permit entry of enzymes and substrates to carry out various cellular functions that would be less efficient or not possible at all in the cytoplasm. (
  • Cytoplasm refers to the jelly-like material with organelles in it. (
  • Primary cilia, the single cilium that protrudes from many mammalian cells, are hybrid organelles with a membrane surrounding the portion that extends from the cell and a portion that is contiguous with the cytoplasm. (
  • c. they allow different chemical reactions within the cell to operate simultaneously without interference from the cytoplasm or other reactions happening in different organelles. (
  • this would illustrate that methodologies developed for studying the biogenesis of the structure-function relationships in one organelle can often be applied fruitfully to investi- gate such aspects in other organelles. (
  • One of the protein complexes involved in this process is biogenesis of lysosome-related organelles complex 1 (BLOC-1). (
  • In losing their autonomy, endosymbionts lost the bulk of their genomes, necessitating the evolution of elaborate mechanisms for organelle biogenesis and metabolite exchange. (
  • The centre focuses on understanding the biogenesis and functions of three organelles, namely, Golgi, TGN and EXPO. (
  • This research will not only address the fundamental questions concerning organelle biogenesis and functions in important biological processes, such as cell wall formation and stress signaling pathways in plants, but will also have potential applications for the biotechnology industry in Hong Kong and China, including improving the value of plants as biofuel feedstocks and enhancing crop productivity in high-stress environments. (
  • Thus, the aim of this Research Topic is to extend our understanding of plant autophagy processes that degrade specific organelles during plant development. (
  • Physiological roles of organelles autophagy in plant development and crop productivity. (
  • Relationship among autophagy and other processes for organelle turnover. (
  • Autophagy is induced upon cellular stress, such as starvation, organelle damage, pathogen invasion, and oxidative stress ( 11 ), and serves as a prosurvival response because mice with a defect in the autophagic response die upon neonatal starvation ( 12 ). (
  • Moreover, the dynamics of processes that result in changes in these characteristics (e.g. organelle fission, fusion, autophagy, transport) influence the function of the cell. (
  • Our experiments suggest an unexpected role for the positioning and inheritance of cellular organelles , in this case enzyme-filled peroxisomes, in controlling this intricate balance," said senior author Elaine Fuchs. (
  • Discovered and isolated by cell biologist Nancy Kedersha and biochemist Leonard Rome in 1986, vaults are cytoplasmic organelles which when negative-stained and viewed under an electron microscope resemble the arches of a cathedral vaulted ceiling, with 39-fold (Or D39d) symmetry. (
  • Cilia and flagella are important organelles of motility , that is, they allow the cell to move. (
  • As you probably all know glycosomes are the membrane surrounded microbody-like organelles of trypanosomatid and bodonid flagellated protists that belong to the order of the Kinetoplastida. (
  • Sequence determination of complete organelle genomes provides the data for genome bioinformatics, the investigation of organelle genome evolution and the molecular phylogeny of protists . (
  • Inside every cell is a complex infrastructure of organelles carrying out different functions. (
  • A third objective was to impress upon the participants that a study of the interaction between different organelles is intrinsic to understanding their physiological functions. (
  • Other membraneless organelles are found only in certain cell types, where they have more-specialized functions. (
  • Lysosome-related organelles occur in specific cell types and fulfil specialised functions e.g. melanosomes which synthesise and store pigments in higher eukaryotes. (
  • Yunfeng Lu has developed a nanoscale shell that can mimic organelles by delivering precisely formulated enzyme combinations intact into the body to serve therapeutic functions. (
  • The functions of the human cell and its organelles are similar to that of a city. (
  • We provide brief summaries of these issues for individual organelles, and conclude with a discussion on how to apply this concept to better understand the mechanisms of size control in the cellular environment. (
  • The study authors said that by using the structural data from this paper, researchers can design experiments to study the mechanisms for how the molecules get across this protein membrane, and to build custom organelles for carbon capture or to produce valuable compounds. (
  • One of the objectives of the course was to compare different organelles in order to allow the participants to discern recurrent themes which would illustrate that a basic unity exists in spite of the diversity. (
  • This suggests that further processing of the RNA molecules takes place step by step in different organelles," says Weis. (
  • While prokaryotes do not possess organelles per se, some do contain protein-based bacterial microcompartments, which are thought to act as primitive organelles. (
  • In particular, Organelle DB is a central repository of yeast protein localization data, incorporating results from both previous and current (ongoing) large-scale studies of protein localization in Saccharomyces cerevisiae. (
  • The special biophysical conditions found in this organelle prevent harmful protein aggregation. (
  • This accumulation in membranous organelles insulates both recombinant protein and host from undesirable activities of either. (
  • Individual organelles are usually separately enclosed within their own lipid bilayers. (
  • The detailed structure of organelles only became clear after the development of the transmission electron microscope (TEM), which made it possible to look at individual organelles at high resolution. (
  • Membraneless organelles, defined as subcellular compartments that lack a surrounding membrane and perform a specialized biochemical role, are also referred to as membraneless compartments, cellular bodies, and, most broadly, biomolecular condensates. (
  • But already, it is clear that the phenomenon underpins the formation and functionality of a growing number of long-observed membraneless organelles. (
  • Now, together with his team, he has researched the principle underpinning the formation of membraneless organelles and how this process is regulated. (
  • By doing so, they realised that it is precisely these flexible arms that are responsible for the formation and regulation of membraneless organelles. (
  • However, membraneless organelles are susceptible to failure. (
  • Now that the biochemists have understood how such membraneless organelles are regulated, they are able to study the phenomenon in a more targeted way. (
  • Indeed four of them refer to organelles of glycogen metabolism, the first of which appeared in Russian in 1977, followed then by a few others. (
  • Researchers at McGill University have discovered bacterial organelles involved in gene expression, suggesting that bacteria may not be as simple as once thought. (
  • The organelles likely evolved from bacteria that were endocytosed more than one billion years ago. (
  • These organelles, or bacterial microcompartments (BMCs), are used by some bacteria to fix carbon dioxide, Kerfeld noted. (
  • This class of organelles also helps many types of pathogenic bacteria metabolize compounds that are not available to normal, non-pathogenic microbes, giving the pathogens a competitive advantage. (
  • Flagellar motors in polarly-flagellated bacteria are excellent examples of organelles that are spatially and numerically regulated in specific bacterial species. (
  • Prokaryotes were once thought not to have organelles, but some examples have now been identified. (
  • By delivering functional enzyme complexes the nanocapsules made of nontoxic polymer "almost mimics an organelle," explained Lu, a professor of chemical and biomolecular engineering. (
  • Researchers are using new technologies to see and understand the networks that connect these organelles, allowing them to build maps of the trade routes that exist within a cell. (
  • Researchers are discovering a growing number of biological processes that take place in these organelles, separated from the rest of the cell's content," says Karsten Weis, Professor of Biochemistry at ETH Zurich. (
  • As such the glycosomes are bonafide organelles tha have established their name in the parasitological, biochemical, cell biological and molecular biological literature. (
  • It turns out that the enhanced MAM formation in obesity is too much of a good thing, leading to functional failure of multiple organelles and amplification of cellular stress," Hotamisligil said. (
  • Each organelle or organized functional macromolecular complex could have an entire article devoted to it. (
  • citation needed] While most cell biologists consider the term organelle to be synonymous with "cell compartment", other cell biologists choose to limit the term organelle to include only those that are containing deoxyribonucleic acid (DNA), having originated from formerly autonomous microscopic organisms acquired via endosymbiosis. (
  • From the green revolution to golden rice, plant organelles have revolutionized agriculture. (
  • After my talk and evaluating several posters presented by investigators from my laboratory, Dr. Jacco Flipsen, Publishing Manager of Kluwer Publishers asked me whether I would consider editing a book on Plant Organelles. (
  • Mutations in BLOC-1 subunits are associated with Hermansky-Pudlak syndrome - a disorder characterised by deficiencies in melanosomes, platelet-dense granules and other lysosome-related organelles. (
  • The removal of damaged organelles is essential for plants throughout various developmental stages as well as to overcome environmental changes that enhance cellular damage, since organelle degradation allows the recycling of derived small molecules, such as amino acids, lipids and nucleic acids. (