DNA-binding motifs formed from two alpha-helixes which intertwine for about eight turns into a coiled coil and then bifurcate to form Y shaped structures. Leucines occurring in heptad repeats end up on the same sides of the helixes and are adjacent to each other in the stem of the Y (the "zipper" region). The DNA-binding residues are located in the bifurcated region of the Y.

A multifunctional iron-sulfur protein that is both an iron regulatory protein and cytoplasmic form of aconitate hydratase. It binds to iron regulatory elements found on mRNAs involved in iron metabolism and regulates their translation. Its RNA binding ability and its aconitate hydrolase activity are dependent upon availability of IRON.

A multifunctional iron-sulfur protein that is both an iron regulatory protein and cytoplasmic form of aconitate hydratase. It binds to iron regulatory elements found on mRNAs involved in iron metabolism and regulates their translation. Its rate of degradation is increased in the presence of IRON.

A LEUCINE and DNA-binding protein that is found primarily in BACTERIA and ARCHAEA. It regulates GENETIC TRANSCRIPTION involved in METABOLISM of AMINO ACIDS in response to the increased concentration of LEUCINE.

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.

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.

Proteins that regulate cellular and organismal iron homeostasis. They play an important biological role by maintaining iron levels that are adequate for metabolic need, but below the toxicity threshold.

The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.

A zinc containing enzyme of the hydrolase class that catalyzes the removal of the N-terminal amino acid from most L-peptides, particularly those with N-terminal leucine residues but not those with N-terminal lysine or arginine residues. This occurs in tissue cell cytosol, with high activity in the duodenum, liver, and kidney. The activity of this enzyme is commonly assayed using a leucine arylamide chromogenic substrate such as leucyl beta-naphthylamide.

Endogenous substances, usually proteins, which are effective in the initiation, stimulation, or termination of the genetic transcription process.

Proteins found in any species of bacterium.

Any of the processes by which cytoplasmic or intercellular factors influence the differential control of gene action in bacteria.

Proteins which bind to DNA. The family includes proteins which bind to both double- and single-stranded DNA and also includes specific DNA binding proteins in serum which can be used as markers for malignant diseases.

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.

'Keto acids', also known as ketone bodies, are water-soluble compounds - acetoacetic acid, beta-hydroxybutyric acid, and acetone - that are produced during fat metabolism when liver glycogen stores are depleted, providing an alternative energy source for the brain and other organs in states of carbohydrate restriction or intense physical exertion.

The biosynthesis of RNA carried out on a template of DNA. The biosynthesis of DNA from an RNA template is called REVERSE TRANSCRIPTION.

The parts of a macromolecule that directly participate in its specific combination with another molecule.

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.

GPI-linked membrane proteins broadly distributed among hematopoietic and non-hematopoietic cells. CD55 prevents the assembly of C3 CONVERTASE or accelerates the disassembly of preformed convertase, thus blocking the formation of the membrane attack complex.

Organic compounds that generally contain an amino (-NH2) and a carboxyl (-COOH) group. Twenty alpha-amino acids are the subunits which are polymerized to form proteins.

The rate dynamics in chemical or physical systems.

An essential branched-chain aliphatic amino acid found in many proteins. It is an isomer of LEUCINE. It is important in hemoglobin synthesis and regulation of blood sugar and energy levels.

An octameric enzyme belonging to the superfamily of amino acid dehydrogenases. Leucine dehydrogenase catalyzes the reversible oxidative deamination of L-LEUCINE, to 4-methyl-2-oxopentanoate (2-ketoisocaproate) and AMMONIA, with the corresponding reduction of the cofactor NAD+.

A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc.

DNA sequences which are recognized (directly or indirectly) and bound by a DNA-dependent RNA polymerase during the initiation of transcription. Highly conserved sequences within the promoter include the Pribnow box in bacteria and the TATA BOX in eukaryotes.

Proteins which maintain the transcriptional quiescence of specific GENES or OPERONS. Classical repressor proteins are DNA-binding proteins that are normally bound to the OPERATOR REGION of an operon, or the ENHANCER SEQUENCES of a gene until a signal occurs that causes their release.

Established cell cultures that have the potential to propagate indefinitely.

Regulatory proteins that act as molecular switches. They control a wide range of biological processes including: receptor signaling, intracellular signal transduction pathways, and protein synthesis. Their activity is regulated by factors that control their ability to bind to and hydrolyze GTP to GDP. EC 3.6.1.-.

Small glycoproteins found on both hematopoietic and non-hematopoietic cells. CD59 restricts the cytolytic activity of homologous complement by binding to C8 and C9 and blocking the assembly of the membrane attack complex. (From Barclay et al., The Leukocyte Antigen FactsBook, 1993, p234)

RNA sequences that serve as templates for protein synthesis. Bacterial mRNAs are generally primary transcripts in that they do not require post-transcriptional processing. Eukaryotic mRNA is synthesized in the nucleus and must be exported to the cytoplasm for translation. Most eukaryotic mRNAs have a sequence of polyadenylic acid at the 3' end, referred to as the poly(A) tail. The function of this tail is not known for certain, but it may play a role in the export of mature mRNA from the nucleus as well as in helping stabilize some mRNA molecules by retarding their degradation in the cytoplasm.

Genes which regulate or circumscribe the activity of other genes; specifically, genes which code for PROTEINS or RNAs which have GENE EXPRESSION REGULATION functions.

A group of enzymes that catalyzes the conversion of ATP and D-glucose to ADP and D-glucose 6-phosphate. They are found in invertebrates and microorganisms, and are highly specific for glucose. (Enzyme Nomenclature, 1992) EC 2.7.1.2.

Phosphoproteins are proteins that have been post-translationally modified with the addition of a phosphate group, usually on serine, threonine or tyrosine residues, which can play a role in their regulation, function, interaction with other molecules, and localization within the cell.

The degree of similarity between sequences of amino acids. This information is useful for the analyzing genetic relatedness of proteins and species.

In bacteria, a group of metabolically related genes, with a common promoter, whose transcription into a single polycistronic MESSENGER RNA is under the control of an OPERATOR REGION.

Proteins that are coded by immediate-early genes, in the absence of de novo protein synthesis. The term was originally used exclusively for viral regulatory proteins that were synthesized just after viral integration into the host cell. It is also used to describe cellular proteins which are synthesized immediately after the resting cell is stimulated by extracellular signals.

Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control (induction or repression) of gene action at the level of transcription or translation.

Amino acids which have a branched carbon chain.

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.

Transport proteins that carry specific substances in the blood or across cell membranes.

A large superfamily of transcription factors that contain a region rich in BASIC AMINO ACID residues followed by a LEUCINE ZIPPER domain.

A family of signal transducing adaptor proteins that control the METABOLISM of NITROGEN. They are primarily found in prokaryotes.

Diffusible gene products that act on homologous or heterologous molecules of viral or cellular DNA to regulate the expression of proteins.

A ubiquitously expressed complement receptor that binds COMPLEMENT C3B and COMPLEMENT C4B and serves as a cofactor for their inactivation. CD46 also interacts with a wide variety of pathogens and mediates immune response.

The biosynthesis of PEPTIDES and PROTEINS on RIBOSOMES, directed by MESSENGER RNA, via TRANSFER RNA that is charged with standard proteinogenic AMINO ACIDS.

A branched-chain essential amino acid that has stimulant activity. It promotes muscle growth and tissue repair. It is a precursor in the penicillin biosynthetic pathway.

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.

The functional hereditary units of BACTERIA.

Extrachromosomal, usually CIRCULAR DNA molecules that are self-replicating and transferable from one organism to another. They are found in a variety of bacterial, archaeal, fungal, algal, and plant species. They are used in GENETIC ENGINEERING as CLONING VECTORS.

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.

Proteins that bind to RNA molecules. Included here are RIBONUCLEOPROTEINS and other proteins whose function is to bind specifically to RNA.

An enzyme that catalyzes the reversible hydration of cis-aconitate to yield citrate or isocitrate. It is one of the citric acid cycle enzymes. EC 4.2.1.3.

A ubiquitously expressed membrane glycoprotein. It interacts with a variety of INTEGRINS and mediates responses to EXTRACELLULAR MATRIX PROTEINS.

Proteins prepared by recombinant DNA technology.

A metallic element with atomic symbol Fe, atomic number 26, and atomic weight 55.85. It is an essential constituent of HEMOGLOBINS; CYTOCHROMES; and IRON-BINDING PROTEINS. It plays a role in cellular redox reactions and in the transport of OXYGEN.

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.

Proteins obtained from ESCHERICHIA COLI.

An essential aromatic amino acid that is a precursor of MELANIN; DOPAMINE; noradrenalin (NOREPINEPHRINE), and THYROXINE.

Genetically engineered MUTAGENESIS at a specific site in the DNA molecule that introduces a base substitution, or an insertion or deletion.

A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine).

The introduction of a phosphoryl group into a compound through the formation of an ester bond between the compound and a phosphorus moiety.

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.

A PYRIDOXAL PHOSPHATE containing enzyme that catalyzes the reversible transamination of branched-chain AMINO ACIDS to 2-oxoglutarate.

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.

The uptake of naked or purified DNA by CELLS, usually meaning the process as it occurs in eukaryotic cells. It is analogous to bacterial transformation (TRANSFORMATION, BACTERIAL) and both are routinely employed in GENE TRANSFER TECHNIQUES.

A mitochondrial cytochrome P450 enzyme that catalyzes the side-chain cleavage of C27 cholesterol to C21 pregnenolone in the presence of molecular oxygen and NADPH-FERRIHEMOPROTEIN REDUCTASE. This enzyme, encoded by CYP11A1 gene, catalyzes the breakage between C20 and C22 which is the initial and rate-limiting step in the biosynthesis of various gonadal and adrenal steroid hormones.

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.

Serum proteins that negatively regulate the cascade process of COMPLEMENT ACTIVATION. Uncontrolled complement activation and resulting cell lysis is potentially dangerous for the host. The complement system is tightly regulated by inactivators that accelerate the decay of intermediates and certain cell surface receptors.

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.

Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures.

The characteristic 3-dimensional shape of a protein, including the secondary, supersecondary (motifs), tertiary (domains) and quaternary structure of the peptide chain. PROTEIN STRUCTURE, QUATERNARY describes the conformation assumed by multimeric proteins (aggregates of more than one polypeptide chain).

A group of proteins possessing only the iron-sulfur complex as the prosthetic group. These proteins participate in all major pathways of electron transport: photosynthesis, respiration, hydroxylation and bacterial hydrogen and nitrogen fixation.

Proteins found in the nucleus of a cell. Do not confuse with NUCLEOPROTEINS which are proteins conjugated with nucleic acids, that are not necessarily present in the nucleus.

Proteins found in any species of fungus.

A set of BACTERIAL ADHESINS and TOXINS, BIOLOGICAL produced by BORDETELLA organisms that determine the pathogenesis of BORDETELLA INFECTIONS, such as WHOOPING COUGH. They include filamentous hemagglutinin; FIMBRIAE PROTEINS; pertactin; PERTUSSIS TOXIN; ADENYLATE CYCLASE TOXIN; dermonecrotic toxin; tracheal cytotoxin; Bordetella LIPOPOLYSACCHARIDES; and tracheal colonization factor.

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.

A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances.

An enzyme that catalyzes the first step in the biosynthetic pathway to LEUCINE, forming isopropyl malate from acetyl-CoA and alpha-ketoisovaleric acid. This enzyme was formerly listed as EC 4.1.3.12.

The protein constituents of muscle, the major ones being ACTINS and MYOSINS. More than a dozen accessory proteins exist including TROPONIN; TROPOMYOSIN; and DYSTROPHIN.

An enzyme of the lyase class that catalyzes the formation of CYCLIC AMP and pyrophosphate from ATP. EC 4.6.1.1.

Guanosine 5'-(trihydrogen diphosphate), monoanhydride with phosphorothioic acid. A stable GTP analog which enjoys a variety of physiological actions such as stimulation of guanine nucleotide-binding proteins, phosphoinositide hydrolysis, cyclic AMP accumulation, and activation of specific proto-oncogenes.

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.

Electrophoresis in which a polyacrylamide gel is used as the diffusion medium.

The process by which two molecules of the same chemical composition form a condensation product or polymer.

A broad category of viral proteins that play indirect roles in the biological processes and activities of viruses. Included here are proteins that either regulate the expression of viral genes or are involved in modifying host cell functions. Many of the proteins in this category serve multiple functions.

An ester formed between the aldehydic carbon of RIBOSE and the terminal phosphate of ADENOSINE DIPHOSPHATE. It is produced by the hydrolysis of nicotinamide-adenine dinucleotide (NAD) by a variety of enzymes, some of which transfer an ADP-ribosyl group to target proteins.

The relationship between the chemical structure of a compound and its biological or pharmacological activity. Compounds are often classed together because they have structural characteristics in common including shape, size, stereochemical arrangement, and distribution of functional groups.

Any of the processes by which cytoplasmic factors influence the differential control of gene action in viruses.

Proteins that control the CELL DIVISION CYCLE. This family of proteins includes a wide variety of classes, including CYCLIN-DEPENDENT KINASES, mitogen-activated kinases, CYCLINS, and PHOSPHOPROTEIN PHOSPHATASES as well as their putative substrates such as chromatin-associated proteins, CYTOSKELETAL PROTEINS, and TRANSCRIPTION FACTORS.

Short sequences (generally about 10 base pairs) of DNA that are complementary to sequences of messenger RNA and allow reverse transcriptases to start copying the adjacent sequences of mRNA. Primers are used extensively in genetic and molecular biology techniques.

One of the virulence factors produced by BORDETELLA PERTUSSIS. It is a multimeric protein composed of five subunits S1 - S5. S1 contains mono ADPribose transferase activity.

Compounds and molecular complexes that consist of very large numbers of atoms and are generally over 500 kDa in size. In biological systems macromolecular substances usually can be visualized using ELECTRON MICROSCOPY and are distinguished from ORGANELLES by the lack of a membrane structure.

Processes that stimulate the GENETIC TRANSCRIPTION of a gene or set of genes.

Guanosine 5'-(tetrahydrogen triphosphate). A guanine nucleotide containing three phosphate groups esterified to the sugar moiety.

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.

Proteins found in any species of virus.

The lipid- and protein-containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells.

Use of restriction endonucleases to analyze and generate a physical map of genomes, genes, or other segments of DNA.

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.

Stable carbon atoms that have the same atomic number as the element carbon, but differ in atomic weight. C-13 is a stable carbon isotope.

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.

Deoxyribonucleic acid that makes up the genetic material of bacteria.

The regulatory elements of an OPERON to which activators or repressors bind thereby effecting the transcription of GENES in the operon.

Domesticated bovine animals of the genus Bos, usually kept on a farm or ranch and used for the production of meat or dairy products or for heavy labor.

A protein found in the thin filaments of muscle fibers. It inhibits contraction of the muscle unless its position is modified by TROPONIN.

A non-hydrolyzable analog of GTP, in which the oxygen atom bridging the beta to the gamma phosphate is replaced by a nitrogen atom. It binds tightly to G-protein in the presence of Mg2+. The nucleotide is a potent stimulator of ADENYLYL CYCLASES.

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)

One of the virulence factors produced by virulent BORDETELLA organisms. It is a bifunctional protein with both ADENYLYL CYCLASES and hemolysin components.

Screening techniques first developed in yeast to identify genes encoding interacting proteins. Variations are used to evaluate interplay between proteins and other molecules. Two-hybrid techniques refer to analysis for protein-protein interactions, one-hybrid for DNA-protein interactions, three-hybrid interactions for RNA-protein interactions or ligand-based interactions. Reverse n-hybrid techniques refer to analysis for mutations or other small molecules that dissociate known interactions.

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.

The sum of the weight of all the atoms in a molecule.

The sequential activation of serum COMPLEMENT PROTEINS to create the COMPLEMENT MEMBRANE ATTACK COMPLEX. Factors initiating complement activation include ANTIGEN-ANTIBODY COMPLEXES, microbial ANTIGENS, or cell surface POLYSACCHARIDES.

A family of enzymes that catalyze the conversion of ATP and a protein to ADP and a phosphoprotein.

The complex series of phenomena, occurring between the end of one CELL DIVISION and the end of the next, by which cellular material is duplicated and then divided between two daughter cells. The cell cycle includes INTERPHASE, which includes G0 PHASE; G1 PHASE; S PHASE; and G2 PHASE, and CELL DIVISION PHASE.

Nucleotides in which the base moiety is substituted with one or more sulfur atoms.

An element with the atomic symbol N, atomic number 7, and atomic weight [14.00643; 14.00728]. Nitrogen exists as a diatomic gas and makes up about 78% of the earth's atmosphere by volume. It is a constituent of proteins and nucleic acids and found in all living cells.

Iron-containing proteins that are widely distributed in animals, plants, and microorganisms. Their major function is to store IRON in a nontoxic bioavailable form. Each ferritin molecule consists of ferric iron in a hollow protein shell (APOFERRITINS) made of 24 subunits of various sequences depending on the species and tissue types.

Single-stranded complementary DNA synthesized from an RNA template by the action of RNA-dependent DNA polymerase. cDNA (i.e., complementary DNA, not circular DNA, not C-DNA) is used in a variety of molecular cloning experiments as well as serving as a specific hybridization probe.

The phenotypic manifestation of a gene or genes by the processes of GENETIC TRANSCRIPTION and GENETIC TRANSLATION.

Trans-acting nuclear proteins whose functional expression are required for retroviral replication. Specifically, the rev gene products are required for processing and translation of the gag and env mRNAs, and thus rev regulates the expression of the viral structural proteins. rev can also regulate viral regulatory proteins. A cis-acting antirepression sequence (CAR) in env, also known as the rev-responsive element (RRE), is responsive to the rev gene product. rev is short for regulator of virion.

Elements of limited time intervals, contributing to particular results or situations.

A transcription factor found in BACTERIA that positively and negatively regulates the expression of proteins required for the uptake and catabolism of L-ARABINOSE.

Process of generating a genetic MUTATION. It may occur spontaneously or be induced by MUTAGENS.

The sequential correspondence of nucleotides in one nucleic acid molecule with those of another nucleic acid molecule. Sequence homology is an indication of the genetic relatedness of different organisms and gene function.

The species Oryctolagus cuniculus, in the family Leporidae, order LAGOMORPHA. Rabbits are born in burrows, furless, and with eyes and ears closed. In contrast with HARES, rabbits have 22 chromosome pairs.

A test used to determine whether or not complementation (compensation in the form of dominance) will occur in a cell with a given mutant phenotype when another mutant genome, encoding the same mutant phenotype, is introduced into that cell.

A chemical reaction in which an electron is transferred from one molecule to another. The electron-donating molecule is the reducing agent or reductant; the electron-accepting molecule is the oxidizing agent or oxidant. Reducing and oxidizing agents function as conjugate reductant-oxidant pairs or redox pairs (Lehninger, Principles of Biochemistry, 1982, p471).

The naturally occurring or experimentally induced replacement of one or more AMINO ACIDS in a protein with another. If a functionally equivalent amino acid is substituted, the protein may retain wild-type activity. Substitution may also diminish, enhance, or eliminate protein function. Experimentally induced substitution is often used to study enzyme activities and binding site properties.

An ENTEROTOXIN from VIBRIO CHOLERAE. It consists of two major protomers, the heavy (H) or A subunit and the B protomer which consists of 5 light (L) or B subunits. The catalytic A subunit is proteolytically cleaved into fragments A1 and A2. The A1 fragment is a MONO(ADP-RIBOSE) TRANSFERASE. The B protomer binds cholera toxin to intestinal epithelial cells, and facilitates the uptake of the A1 fragment. The A1 catalyzed transfer of ADP-RIBOSE to the alpha subunits of heterotrimeric G PROTEINS activates the production of CYCLIC AMP. Increased levels of cyclic AMP are thought to modulate release of fluid and electrolytes from intestinal crypt cells.

Proteins encoded by the REV GENES of the HUMAN IMMUNODEFICIENCY VIRUS.

Molecules on the surface of some B-lymphocytes and macrophages, that recognize and combine with the C3b, C3d, C1q, and C4b components of complement.

A species of CERCOPITHECUS containing three subspecies: C. tantalus, C. pygerythrus, and C. sabeus. They are found in the forests and savannah of Africa. The African green monkey (C. pygerythrus) is the natural host of SIMIAN IMMUNODEFICIENCY VIRUS and is used in AIDS research.

A set of genes descended by duplication and variation from some ancestral gene. Such genes may be clustered together on the same chromosome or dispersed on different chromosomes. Examples of multigene families include those that encode the hemoglobins, immunoglobulins, histocompatibility antigens, actins, tubulins, keratins, collagens, heat shock proteins, salivary glue proteins, chorion proteins, cuticle proteins, yolk proteins, and phaseolins, as well as histones, ribosomal RNA, and transfer RNA genes. The latter three are examples of reiterated genes, where hundreds of identical genes are present in a tandem array. (King & Stanfield, A Dictionary of Genetics, 4th ed)

Serum glycoproteins participating in the host defense mechanism of COMPLEMENT ACTIVATION that creates the COMPLEMENT MEMBRANE ATTACK COMPLEX. Included are glycoproteins in the various pathways of complement activation (CLASSICAL COMPLEMENT PATHWAY; ALTERNATIVE COMPLEMENT PATHWAY; and LECTIN COMPLEMENT PATHWAY).

The level of protein structure in which regular hydrogen-bond interactions within contiguous stretches of polypeptide chain give rise to alpha helices, beta strands (which align to form beta sheets) or other types of coils. This is the first folding level of protein conformation.

A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement.

A non-essential amino acid that occurs in high levels in its free state in plasma. It is produced from pyruvate by transamination. It is involved in sugar and acid metabolism, increases IMMUNITY, and provides energy for muscle tissue, BRAIN, and the CENTRAL NERVOUS SYSTEM.

A group of enzymes that catalyzes the hydrolysis of terminal, non-reducing beta-D-galactose residues in beta-galactosides. Deficiency of beta-Galactosidase A1 may cause GANGLIOSIDOSIS, GM1.

Commonly observed structural components of proteins formed by simple combinations of adjacent secondary structures. A commonly observed structure may be composed of a CONSERVED SEQUENCE which can be represented by a CONSENSUS SEQUENCE.

A diverse class of enzymes that interact with UBIQUITIN-CONJUGATING ENZYMES and ubiquitination-specific protein substrates. Each member of this enzyme group has its own distinct specificity for a substrate and ubiquitin-conjugating enzyme. Ubiquitin-protein ligases exist as both monomeric proteins multiprotein complexes.

Nucleic acid sequences involved in regulating the expression of genes.

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.

CELL LINES derived from the CV-1 cell line by transformation with a replication origin defective mutant of SV40 VIRUS, which codes for wild type large T antigen (ANTIGENS, POLYOMAVIRUS TRANSFORMING). They are used for transfection and cloning. (The CV-1 cell line was derived from the kidney of an adult male African green monkey (CERCOPITHECUS AETHIOPS).)

Guanine nucleotides are cyclic or linear molecules that consist of a guanine base, a pentose sugar (ribose in the cyclic form, deoxyribose in the linear form), and one or more phosphate groups, playing crucial roles in signal transduction, protein synthesis, and regulation of enzymatic activities.

A method for determining the sequence specificity of DNA-binding proteins. DNA footprinting utilizes a DNA damaging agent (either a chemical reagent or a nuclease) which cleaves DNA at every base pair. DNA cleavage is inhibited where the ligand binds to DNA. (from Rieger et al., Glossary of Genetics: Classical and Molecular, 5th ed)

An electrophoretic technique for assaying the binding of one compound to another. Typically one compound is labeled to follow its mobility during electrophoresis. If the labeled compound is bound by the other compound, then the mobility of the labeled compound through the electrophoretic medium will be retarded.

The outward appearance of the individual. It is the product of interactions between genes, and between the GENOTYPE and the environment.

A non-essential amino acid present abundantly throughout the body and is involved in many metabolic processes. It is synthesized from GLUTAMIC ACID and AMMONIA. It is the principal carrier of NITROGEN in the body and is an important energy source for many cells.

An important soluble regulator of the alternative pathway of complement activation (COMPLEMENT ACTIVATION PATHWAY, ALTERNATIVE). It is a 139-kDa glycoprotein expressed by the liver and secreted into the blood. It binds to COMPLEMENT C3B and makes iC3b (inactivated complement 3b) susceptible to cleavage by COMPLEMENT FACTOR I. Complement factor H also inhibits the association of C3b with COMPLEMENT FACTOR B to form the C3bB proenzyme, and promotes the dissociation of Bb from the C3bBb complex (COMPLEMENT C3 CONVERTASE, ALTERNATIVE PATHWAY).

A multistage process that includes cloning, physical mapping, subcloning, determination of the DNA SEQUENCE, and information analysis.

Cells grown in vitro from neoplastic tissue. If they can be established as a TUMOR CELL LINE, they can be propagated in cell culture indefinitely.

A source of inorganic fluoride which is used topically to prevent dental caries.

Conversion of an inactive form of an enzyme to one possessing metabolic activity. It includes 1, activation by ions (activators); 2, activation by cofactors (coenzymes); and 3, conversion of an enzyme precursor (proenzyme or zymogen) to an active enzyme.

A sequence of successive nucleotide triplets that are read as CODONS specifying AMINO ACIDS and begin with an INITIATOR CODON and end with a stop codon (CODON, TERMINATOR).

Deletion of sequences of nucleic acids from the genetic material of an individual.

Fructosephosphates are organic compounds resulting from the combination of fructose with a phosphate group, playing crucial roles in various metabolic processes, particularly within carbohydrate metabolism.

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.

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.

Members of the class of compounds composed of AMINO ACIDS joined together by peptide bonds between adjacent amino acids into linear, branched or cyclical structures. OLIGOPEPTIDES are composed of approximately 2-12 amino acids. Polypeptides are composed of approximately 13 or more amino acids. PROTEINS are linear polypeptides that are normally synthesized on RIBOSOMES.

Membrane glycoproteins found in high concentrations on iron-utilizing cells. They specifically bind iron-bearing transferrin, are endocytosed with its ligand and then returned to the cell surface where transferrin without its iron is released.

A group of polycyclic compounds closely related biochemically to TERPENES. They include cholesterol, numerous hormones, precursors of certain vitamins, bile acids, alcohols (STEROLS), and certain natural drugs and poisons. Steroids have a common nucleus, a fused, reduced 17-carbon atom ring system, cyclopentanoperhydrophenanthrene. Most steroids also have two methyl groups and an aliphatic side-chain attached to the nucleus. (From Hawley's Condensed Chemical Dictionary, 11th ed)

A 51-amino acid pancreatic hormone that plays a major role in the regulation of glucose metabolism, directly by suppressing endogenous glucose production (GLYCOGENOLYSIS; GLUCONEOGENESIS) and indirectly by suppressing GLUCAGON secretion and LIPOLYSIS. Native insulin is a globular protein comprised of a zinc-coordinated hexamer. Each insulin monomer containing two chains, A (21 residues) and B (30 residues), linked by two disulfide bonds. Insulin is used as a drug to control insulin-dependent diabetes mellitus (DIABETES MELLITUS, TYPE 1).

A species of gram-positive bacteria that is a common soil and water saprophyte.

Detection of RNA that has been electrophoretically separated and immobilized by blotting on nitrocellulose or other type of paper or nylon membrane followed by hybridization with labeled NUCLEIC ACID PROBES.

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)

A characteristic feature of enzyme activity in relation to the kind of substrate on which the enzyme or catalytic molecule reacts.

A genetic rearrangement through loss of segments of DNA or RNA, bringing sequences which are normally separated into close proximity. This deletion may be detected using cytogenetic techniques and can also be inferred from the phenotype, indicating a deletion at one specific locus.

In eukaryotes, a genetic unit consisting of a noncontiguous group of genes under the control of a single regulator gene. In bacteria, regulons are global regulatory systems involved in the interplay of pleiotropic regulatory domains and consist of several OPERONS.

Systems of enzymes which function sequentially by catalyzing consecutive reactions linked by common metabolic intermediates. They may involve simply a transfer of water molecules or hydrogen atoms and may be associated with large supramolecular structures such as MITOCHONDRIA or RIBOSOMES.

A transfer RNA which is specific for carrying leucine to sites on the ribosomes in preparation for protein synthesis.

A sequence of amino acids in a polypeptide or of nucleotides in DNA or RNA that is similar across multiple species. A known set of conserved sequences is represented by a CONSENSUS SEQUENCE. AMINO ACID MOTIFS are often composed of conserved sequences.

Trans-acting transcription factors produced by retroviruses such as HIV. They are nuclear proteins whose expression is required for viral replication. The tat protein stimulates LONG TERMINAL REPEAT-driven RNA synthesis for both viral regulatory and viral structural proteins. tat stands for trans-activation of transcription.

One of the minor protein components of skeletal muscle. Its function is to serve as the calcium-binding component in the troponin-tropomyosin B-actin-myosin complex by conferring calcium sensitivity to the cross-linked actin and myosin filaments.

Proteins to which calcium ions are bound. They can act as transport proteins, regulator proteins, or activator proteins. They typically contain EF HAND MOTIFS.

Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control of gene action in fungi.

The protein components of ferritins. Apoferritins are shell-like structures containing nanocavities and ferroxidase activities. Apoferritin shells are composed of 24 subunits, heteropolymers in vertebrates and homopolymers in bacteria. In vertebrates, there are two types of subunits, light chain and heavy chain. The heavy chain contains the ferroxidase activity.

In vitro method for producing large amounts of specific DNA or RNA fragments of defined length and sequence from small amounts of short oligonucleotide flanking sequences (primers). The essential steps include thermal denaturation of the double-stranded target molecules, annealing of the primers to their complementary sequences, and extension of the annealed primers by enzymatic synthesis with DNA polymerase. The reaction is efficient, specific, and extremely sensitive. Uses for the reaction include disease diagnosis, detection of difficult-to-isolate pathogens, mutation analysis, genetic testing, DNA sequencing, and analyzing evolutionary relationships.

An unnatural amino acid that is used experimentally to study protein structure and function. It is structurally similar to METHIONINE, however it does not contain SULFUR.

The processes whereby the internal environment of an organism tends to remain balanced and stable.

An adenine nucleotide containing one phosphate group which is esterified to both the 3'- and 5'-positions of the sugar moiety. It is a second messenger and a key intracellular regulator, functioning as a mediator of activity for a number of hormones, including epinephrine, glucagon, and ACTH.

A variation of the PCR technique in which cDNA is made from RNA via reverse transcription. The resultant cDNA is then amplified using standard PCR protocols.

The functional hereditary units of FUNGI.

A large multisubunit complex that plays an important role in the degradation of most of the cytosolic and nuclear proteins in eukaryotic cells. It contains a 700-kDa catalytic sub-complex and two 700-kDa regulatory sub-complexes. The complex digests ubiquitinated proteins and protein activated via ornithine decarboxylase antizyme.

A protein which is a subunit of RNA polymerase. It effects initiation of specific RNA chains from DNA.

The spatial arrangement of the atoms of a nucleic acid or polynucleotide that results in its characteristic 3-dimensional shape.

Enzymes that hydrolyze GTP to GDP. EC 3.6.1.-.

A guanine nucleotide containing two phosphate groups esterified to the sugar moiety.

A theoretical representative nucleotide or amino acid sequence in which each nucleotide or amino acid is the one which occurs most frequently at that site in the different sequences which occur in nature. The phrase also refers to an actual sequence which approximates the theoretical consensus. A known CONSERVED SEQUENCE set is represented by a consensus sequence. Commonly observed supersecondary protein structures (AMINO ACID MOTIFS) are often formed by conserved sequences.

A strain of albino rat used widely for experimental purposes because of its calmness and ease of handling. It was developed by the Sprague-Dawley Animal Company.

Post-transcriptional regulatory proteins required for the accumulation of mRNAs that encode the gag and env gene products in HUMAN T-LYMPHOTROPIC VIRUS 1 and HUMAN T-LYMPHOTROPIC VIRUS 2. The rex (regulator x; x is undefined) products act by binding to elements in the LONG TERMINAL REPEAT.

(GTP cyclohydrolase I) or GTP 7,8-8,9-dihydrolase (pyrophosphate-forming) (GTP cyclohydrolase II). An enzyme group that hydrolyzes the imidazole ring of GTP, releasing carbon-8 as formate. Two C-N bonds are hydrolyzed and the pentase unit is isomerized. This is the first step in the synthesis of folic acid from GTP. EC 3.5.4.16 (GTP cyclohydrolase I) and EC 3.5.4.25 (GTP cyclohydrolase II).

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.

Monomeric subunits of primarily globular ACTIN and found in the cytoplasmic matrix of almost all cells. They are often associated with microtubules and may play a role in cytoskeletal function and/or mediate movement of the cell or the organelles within the cell.

Proteins encoded by the TAT GENES of the HUMAN IMMUNODEFICIENCY VIRUS.

The first DNA-binding protein motif to be recognized. Helix-turn-helix motifs were originally identified in bacterial proteins but have since been found in hundreds of DNA-BINDING PROTEINS from both eukaryotes and prokaryotes. They are constructed from two alpha helices connected by a short extended chain of amino acids, which constitute the "turn." The two helices are held at a fixed angle, primarily through interactions between the two helices. (From Alberts et al., Molecular Biology of the Cell, 3d ed, p408-9)

A subfamily in the family MURIDAE, comprising the hamsters. Four of the more common genera are Cricetus, CRICETULUS; MESOCRICETUS; and PHODOPUS.

The in vitro fusion of GENES by RECOMBINANT DNA techniques to analyze protein behavior or GENE EXPRESSION REGULATION, or to merge protein functions for specific medical or industrial uses.

Serologic tests in which a positive reaction manifested by visible CHEMICAL PRECIPITATION occurs when a soluble ANTIGEN reacts with its precipitins, i.e., ANTIBODIES that can form a precipitate.

An essential amino acid. It is often added to animal feed.

Amino acids that are not synthesized by the human body in amounts sufficient to carry out physiological functions. They are obtained from dietary foodstuffs.

Biochemical identification of mutational changes in a nucleotide sequence.

Mutagenesis where the mutation is caused by the introduction of foreign DNA sequences into a gene or extragenic sequence. This may occur spontaneously in vivo or be experimentally induced in vivo or in vitro. Proviral DNA insertions into or adjacent to a cellular proto-oncogene can interrupt GENETIC TRANSLATION of the coding sequences or interfere with recognition of regulatory elements and cause unregulated expression of the proto-oncogene resulting in tumor formation.