Transfer RNA Aminoacylation: The conversion of uncharged TRANSFER RNA to AMINO ACYL TRNA.Aminoacylation: A reaction that introduces an aminoacyl group to a molecule. TRANSFER RNA AMINOACYLATION is the first step in GENETIC TRANSLATION.Amino Acyl-tRNA Synthetases: A subclass of enzymes that aminoacylate AMINO ACID-SPECIFIC TRANSFER RNA with their corresponding AMINO ACIDS.Acylation: The addition of an organic acid radical into a molecule.Alanine-tRNA Ligase: An enzyme that activates alanine with its specific transfer RNA. EC 6.1.1.7.Anticodon: The sequential set of three nucleotides in TRANSFER RNA that interacts with its complement in MESSENGER RNA, the CODON, during translation in the ribosome.Leucine-tRNA Ligase: An enzyme that activates leucine with its specific transfer RNA. EC 6.1.1.4.RNA, Transfer, Cys: A transfer RNA which is specific for carrying cysteine to sites on the ribosomes in preparation for protein synthesis.RNA, Transfer, Amino Acyl: Intermediates in protein biosynthesis. The compounds are formed from amino acids, ATP and transfer RNA, a reaction catalyzed by aminoacyl tRNA synthetase. They are key compounds in the genetic translation process.RNA, Transfer: The small RNA molecules, 73-80 nucleotides long, that function during translation (TRANSLATION, GENETIC) to align AMINO ACIDS at the RIBOSOMES in a sequence determined by the mRNA (RNA, MESSENGER). There are about 30 different transfer RNAs. Each recognizes a specific CODON set on the mRNA through its own ANTICODON and as aminoacyl tRNAs (RNA, TRANSFER, AMINO ACYL), each carries a specific amino acid to the ribosome to add to the elongating peptide chains.Phenylalanine-tRNA Ligase: An enzyme that activates phenylalanine with its specific transfer RNA. EC 6.1.1.20.Isoleucine-tRNA Ligase: An enzyme that activates isoleucine with its specific transfer RNA. EC 6.1.1.5.Valine-tRNA Ligase: An enzyme that activates valine with its specific transfer RNA. EC 6.1.1.9RNA, Transfer, Ala: A transfer RNA which is specific for carrying alanine to sites on the ribosomes in preparation for protein synthesis.RNA, Transfer, Leu: A transfer RNA which is specific for carrying leucine to sites on the ribosomes in preparation for protein synthesis.Methionine-tRNA Ligase: An enzyme that activates methionine with its specific transfer RNA. EC 6.1.1.10.Serine-tRNA Ligase: An enzyme that activates serine with its specific transfer RNA. EC 6.1.1.11.RNA, Transfer, Asp: A transfer RNA which is specific for carrying aspartic acid to sites on the ribosomes in preparation for protein synthesis.RNA, Transfer, Val: A transfer RNA which is specific for carrying valine to sites on the ribosomes in preparation for protein synthesis.Aspartate-tRNA Ligase: An enzyme that activates aspartic acid with its specific transfer RNA. EC 6.1.1.12.RNA, Transfer, Ile: A transfer RNA which is specific for carrying isoleucine to sites on the ribosomes in preparation for protein synthesis.Tyrosine-tRNA Ligase: An enzyme that activates tyrosine with its specific transfer RNA. EC 6.1.1.1.Glycine-tRNA Ligase: An enzyme that activates glycine with its specific transfer RNA. EC 6.1.1.14.Lysine-tRNA Ligase: An enzyme that activates lysine with its specific transfer RNA. EC 6.1.1.6.Arginine-tRNA Ligase: An enzyme that activates arginine with its specific transfer RNA. EC 6.1.1.19.Glutamate-tRNA Ligase: An enzyme that activates glutamic acid with its specific transfer RNA. EC 6.1.1.17.Nucleic Acid Conformation: The spatial arrangement of the atoms of a nucleic acid or polynucleotide that results in its characteristic 3-dimensional shape.RNA, Transfer, Pro: A transfer RNA which is specific for carrying proline to sites on the ribosomes in preparation for protein synthesis.RNA, Transfer, Amino Acid-Specific: A group of transfer RNAs which are specific for carrying each one of the 20 amino acids to the ribosome in preparation for protein synthesis.Tryptophan-tRNA Ligase: An enzyme that activates tryptophan with its specific transfer RNA. EC 6.1.1.2.RNA, Transfer, Ser: A transfer RNA which is specific for carrying serine to sites on the ribosomes in preparation for protein synthesis.RNA, Transfer, Trp: A transfer RNA which is specific for carrying tryptophan to sites on the ribosomes in preparation for protein synthesis.Escherichia coli: 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.Threonine-tRNA Ligase: An enzyme that activates threonine with its specific transfer RNA. EC 6.1.1.3.RNA, Transfer, Thr: A transfer RNA which is specific for carrying threonine to sites on the ribosomes in preparation for protein synthesis.RNA, Transfer, Met: A transfer RNA which is specific for carrying methionine to sites on the ribosomes. During initiation of protein synthesis, tRNA(f)Met in prokaryotic cells and tRNA(i)Met in eukaryotic cells binds to the start codon (CODON, INITIATOR).RNA, Transfer, Glu: A transfer RNA which is specific for carrying glutamic acid to sites on the ribosomes in preparation for protein synthesis.RNA, Transfer, Asn: A transfer RNA which is specific for carrying asparagine to sites on the ribosomes in preparation for protein synthesis.RNA, Transfer, Gln: A transfer RNA which is specific for carrying glutamine to sites on the ribosomes in preparation for protein synthesis.RNA, Transfer, Arg: A transfer RNA which is specific for carrying arginine to sites on the ribosomes in preparation for protein synthesis.RNA, Transfer, His: A transfer RNA which is specific for carrying histidine to sites on the ribosomes in preparation for protein synthesis.RNA, Transfer, Tyr: A transfer RNA which is specific for carrying tyrosine to sites on the ribosomes in preparation for protein synthesis.RNA, Transfer, Phe: A transfer RNA which is specific for carrying phenylalanine to sites on the ribosomes in preparation for protein synthesis.RNA Editing: A process that changes the nucleotide sequence of mRNA from that of the DNA template encoding it. Some major classes of RNA editing are as follows: 1, the conversion of cytosine to uracil in mRNA; 2, the addition of variable number of guanines at pre-determined sites; and 3, the addition and deletion of uracils, templated by guide-RNAs (RNA, GUIDE).RNA, Transfer, Gly: A transfer RNA which is specific for carrying glycine to sites on the ribosomes in preparation for protein synthesis.Histidine-tRNA Ligase: An enzyme that activates histidine with its specific transfer RNA. EC 6.1.1.21.Base Sequence: The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.RNA, Bacterial: Ribonucleic acid in bacteria having regulatory and catalytic roles as well as involvement in protein synthesis.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.RNA, Transfer, Lys: A transfer RNA which is specific for carrying lysine to sites on the ribosomes in preparation for protein synthesis.Genetic Code: The meaning ascribed to the BASE SEQUENCE with respect to how it is translated into AMINO ACID SEQUENCE. The start, stop, and order of amino acids of a protein is specified by consecutive triplets of nucleotides called codons (CODON).Kinetics: The rate dynamics in chemical or physical systems.Phenylalanine: An essential aromatic amino acid that is a precursor of MELANIN; DOPAMINE; noradrenalin (NOREPINEPHRINE), and THYROXINE.Diphosphates: Inorganic salts of phosphoric acid that contain two phosphate groups.Substrate Specificity: A characteristic feature of enzyme activity in relation to the kind of substrate on which the enzyme or catalytic molecule reacts.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.Valine: 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.Isoleucine: 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.Amino Acids: 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.Protein Biosynthesis: The biosynthesis of PEPTIDES and PROTEINS on RIBOSOMES, directed by MESSENGER RNA, via TRANSFER RNA that is charged with standard proteinogenic AMINO ACIDS.Tymovirus: A genus of plant viruses, in the family TYMOVIRIDAE, possessing a narrow host range that includes CRUCIFERAE. Transmission occurs by BEETLES and mechanical inoculation.Amination: The creation of an amine. It can be produced by the addition of an amino group to an organic compound or reduction of a nitro group.Thermus thermophilus: A species of gram-negative, aerobic, rod-shaped bacteria found in hot springs of neutral to alkaline pH, as well as in hot-water heaters.Thiouridine: A photoactivable URIDINE analog that is used as an affinity label.Methanobacteriaceae: A family of anaerobic, coccoid to rod-shaped METHANOBACTERIALES. Cell membranes are composed mainly of polyisoprenoid hydrocarbons ether-linked to glycerol. Its organisms are found in anaerobic habitats throughout nature.MELAS Syndrome: A mitochondrial disorder characterized by focal or generalized seizures, episodes of transient or persistent neurologic dysfunction resembling strokes, and ragged-red fibers on muscle biopsy. Affected individuals tend to be normal at birth through early childhood, then experience growth failure, episodic vomiting, and recurrent cerebral insults resulting in visual loss and hemiparesis. The cortical lesions tend to occur in the parietal and occipital lobes and are not associated with vascular occlusion. VASCULAR HEADACHE is frequently associated and the disorder tends to be familial. (From Joynt, Clinical Neurology, 1992, Ch56, p117)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.MERRF Syndrome: A mitochondrial encephalomyopathy characterized clinically by a mixed seizure disorder, myoclonus, progressive ataxia, spasticity, and a mild myopathy. Dysarthria, optic atrophy, growth retardation, deafness, and dementia may also occur. This condition tends to present in childhood and to be transmitted via maternal lineage. Muscle biopsies reveal ragged-red fibers and respiratory chain enzymatic defects. (From Adams et al., Principles of Neurology, 6th ed, p986)Models, Molecular: Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures.Adenosine Monophosphate: Adenine nucleotide containing one phosphate group esterified to the sugar moiety in the 2'-, 3'-, or 5'-position.Binding Sites: The parts of a macromolecule that directly participate in its specific combination with another molecule.Oligoribonucleotides: A group of ribonucleotides (up to 12) in which the phosphate residues of each ribonucleotide act as bridges in forming diester linkages between the ribose moieties.N-Formylmethionine: Effective in the initiation of protein synthesis. The initiating methionine residue enters the ribosome as N-formylmethionyl tRNA. This process occurs in Escherichia coli and other bacteria as well as in the mitochondria of eucaryotic cells.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.RNA Ligase (ATP): An enzyme that catalyzes the conversion of linear RNA to a circular form by the transfer of the 5'-phosphate to the 3'-hydroxyl terminus. It also catalyzes the covalent joining of two polyribonucleotides in phosphodiester linkage. EC 6.5.1.3.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.RNA, Fungal: Ribonucleic acid in fungi having regulatory and catalytic roles as well as involvement in protein synthesis.Structure-Activity Relationship: 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.RNA: A polynucleotide consisting essentially of chains with a repeating backbone of phosphate and ribose units to which nitrogenous bases are attached. RNA is unique among biological macromolecules in that it can encode genetic information, serve as an abundant structural component of cells, and also possesses catalytic activity. (Rieger et al., Glossary of Genetics: Classical and Molecular, 5th ed)Peptide Elongation Factor Tu: A protein found in bacteria and eukaryotic mitochondria which delivers aminoacyl-tRNA's to the A site of the ribosome. The aminoacyl-tRNA is first bound to a complex of elongation factor Tu containing a molecule of bound GTP. The resulting complex is then bound to the 70S initiation complex. Simultaneously the GTP is hydrolyzed and a Tu-GDP complex is released from the 70S ribosome. The Tu-GTP complex is regenerated from the Tu-GDP complex by the Ts elongation factor and GTP.Mosaic Viruses: Viruses which produce a mottled appearance of the leaves of plants.Magnesium: A metallic element that has the atomic symbol Mg, atomic number 12, and atomic weight 24.31. It is important for the activity of many enzymes, especially those involved in OXIDATIVE PHOSPHORYLATION.Yeasts: A general term for single-celled rounded fungi that reproduce by budding. Brewers' and bakers' yeasts are SACCHAROMYCES CEREVISIAE; therapeutic dried yeast is YEAST, DRIED.Base Pairing: Pairing of purine and pyrimidine bases by HYDROGEN BONDING in double-stranded DNA or RNA.Nitrogenous Group Transferases: Enzymes that catalyze the transfer of nitrogenous groups, primarily amino groups, from a donor, generally an amino acid, to an acceptor, usually a 2-oxoacid. EC 2.6.Methionine: A sulfur-containing essential L-amino acid that is important in many body functions.Catalytic Domain: The region of an enzyme that interacts with its substrate to cause the enzymatic reaction.Genes, Suppressor: Genes that have a suppressor allele or suppressor mutation (SUPPRESSION, GENETIC) which cancels the effect of a previous mutation, enabling the wild-type phenotype to be maintained or partially restored. For example, amber suppressors cancel the effect of an AMBER NONSENSE MUTATION.Periodic Acid: A strong oxidizing agent.Alanine: 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.Leucine: An essential branched-chain amino acid important for hemoglobin formation.Catalysis: The facilitation of a chemical reaction by material (catalyst) that is not consumed by the reaction.Ribosomes: Multicomponent ribonucleoprotein structures found in the CYTOPLASM of all cells, and in MITOCHONDRIA, and PLASTIDS. They function in PROTEIN BIOSYNTHESIS via GENETIC TRANSLATION.Ribonuclease T1: An enzyme catalyzing the endonucleolytic cleavage of RNA at the 3'-position of a guanylate residue. EC 3.1.27.3.Codon: A set of three nucleotides in a protein coding sequence that specifies individual amino acids or a termination signal (CODON, TERMINATOR). Most codons are universal, but some organisms do not produce the transfer RNAs (RNA, TRANSFER) complementary to all codons. These codons are referred to as unassigned codons (CODONS, NONSENSE).Lysine: An essential amino acid. It is often added to animal feed.Haloferax volcanii: A species of halophilic archaea found in the Dead Sea.Evolution, Molecular: The process of cumulative change at the level of DNA; RNA; and PROTEINS, over successive generations.RNA, Archaeal: Ribonucleic acid in archaea having regulatory and catalytic roles as well as involvement in protein synthesis.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.Biocatalysis: The facilitation of biochemical reactions with the aid of naturally occurring catalysts such as ENZYMES.Peptide Elongation Factor 1: Peptide elongation factor 1 is a multisubunit protein that is responsible for the GTP-dependent binding of aminoacyl-tRNAs to eukaryotic ribosomes. The alpha subunit (EF-1alpha) binds aminoacyl-tRNA and transfers it to the ribosome in a process linked to GTP hydrolysis. The beta and delta subunits (EF-1beta, EF-1delta) are involved in exchanging GDP for GTP. The gamma subunit (EF-1gamma) is a structural component.Mutagenesis, Site-Directed: Genetically engineered MUTAGENESIS at a specific site in the DNA molecule that introduces a base substitution, or an insertion or deletion.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.Sulfites: Inorganic salts of sulfurous acid.Species Specificity: The restriction of a characteristic behavior, anatomical structure or physical system, such as immune response; metabolic response, or gene or gene variant to the members of one species. It refers to that property which differentiates one species from another but it is also used for phylogenetic levels higher or lower than the species.Geobacillus stearothermophilus: A species of GRAM-POSITIVE ENDOSPORE-FORMING BACTERIA in the family BACILLACEAE, found in soil, hot springs, Arctic waters, ocean sediments, and spoiled food products.Crystallography, X-Ray: The study of crystal structure using X-RAY DIFFRACTION techniques. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)GuanineHydrogen Bonding: A low-energy attractive force between hydrogen and another element. It plays a major role in determining the properties of water, proteins, and other compounds.Plant Viruses: Viruses parasitic on plants higher than bacteria.Suppression, Genetic: Mutation process that restores the wild-type PHENOTYPE in an organism possessing a mutationally altered GENOTYPE. The second "suppressor" mutation may be on a different gene, on the same gene but located at a distance from the site of the primary mutation, or in extrachromosomal genes (EXTRACHROMOSOMAL INHERITANCE).Mitochondrial Diseases: Diseases caused by abnormal function of the MITOCHONDRIA. They may be caused by mutations, acquired or inherited, in mitochondrial DNA or in nuclear genes that code for mitochondrial components. They may also be the result of acquired mitochondria dysfunction due to adverse effects of drugs, infections, or other environmental causes.Peptide Biosynthesis: The production of PEPTIDES or PROTEINS by the constituents of a living organism. The biosynthesis of proteins on RIBOSOMES following an RNA template is termed translation (TRANSLATION, GENETIC). There are other, non-ribosomal peptide biosynthesis (PEPTIDE BIOSYNTHESIS, NUCLEIC ACID-INDEPENDENT) mechanisms carried out by PEPTIDE SYNTHASES and PEPTIDYLTRANSFERASES. Further modifications of peptide chains yield functional peptide and protein molecules.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)Poly U: A group of uridine ribonucleotides in which the phosphate residues of each uridine ribonucleotide act as bridges in forming diester linkages between the ribose moieties.Peptide Elongation Factors: Protein factors uniquely required during the elongation phase of protein synthesis.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.Point Mutation: A mutation caused by the substitution of one nucleotide for another. This results in the DNA molecule having a change in a single base pair.Methanococcus: A genus of anaerobic coccoid METHANOCOCCACEAE whose organisms are motile by means of polar tufts of flagella. These methanogens are found in salt marshes, marine and estuarine sediments, and the intestinal tract of animals.Mutagenesis: Process of generating a genetic MUTATION. It may occur spontaneously or be induced by MUTAGENS.Peptide Chain Elongation, Translational: A process of GENETIC TRANSLATION, when an amino acid is transferred from its cognate TRANSFER RNA to the lengthening chain of PEPTIDES.Hydrolysis: The process of cleaving a chemical compound by the addition of a molecule of water.RNA, Catalytic: RNA that has catalytic activity. The catalytic RNA sequence folds to form a complex surface that can function as an enzyme in reactions with itself and other molecules. It may function even in the absence of protein. There are numerous examples of RNA species that are acted upon by catalytic RNA, however the scope of this enzyme class is not limited to a particular type of substrate.Chemistry: A basic science concerned with the composition, structure, and properties of matter; and the reactions that occur between substances and the associated energy exchange.Tryptophan: An essential amino acid that is necessary for normal growth in infants and for NITROGEN balance in adults. It is a precursor of INDOLE ALKALOIDS in plants. It is a precursor of SEROTONIN (hence its use as an antidepressant and sleep aid). It can be a precursor to NIACIN, albeit inefficiently, in mammals.Archaeoglobus fulgidus: A species of extremely thermophilic, sulfur-reducing archaea. It grows at a maximum temperature of 95 degrees C. in marine or deep-sea geothermal areas.Chemical Phenomena: The composition, conformation, and properties of atoms and molecules, and their reaction and interaction processes.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.Oligonucleotides: Polymers made up of a few (2-20) nucleotides. In molecular genetics, they refer to a short sequence synthesized to match a region where a mutation is known to occur, and then used as a probe (OLIGONUCLEOTIDE PROBES). (Dorland, 28th ed)RNA Nucleotidyltransferases: Enzymes that catalyze the template-directed incorporation of ribonucleotides into an RNA chain. EC 2.7.7.-.Pyrophosphatases: A group of enzymes within the class EC 3.6.1.- that catalyze the hydrolysis of diphosphate bonds, chiefly in nucleoside di- and triphosphates. They may liberate either a mono- or diphosphate. EC 3.6.1.-.Models, Chemical: Theoretical representations that simulate the behavior or activity of chemical processes or phenomena; includes the use of mathematical equations, computers, and other electronic equipment.Cytosine: A pyrimidine base that is a fundamental unit of nucleic acids.UridineArchaea: One of the three domains of life (the others being BACTERIA and Eukarya), formerly called Archaebacteria under the taxon Bacteria, but now considered separate and distinct. They are characterized by: (1) the presence of characteristic tRNAs and ribosomal RNAs; (2) the absence of peptidoglycan cell walls; (3) the presence of ether-linked lipids built from branched-chain subunits; and (4) their occurrence in unusual habitats. While archaea resemble bacteria in morphology and genomic organization, they resemble eukarya in their method of genomic replication. The domain contains at least four kingdoms: CRENARCHAEOTA; EURYARCHAEOTA; NANOARCHAEOTA; and KORARCHAEOTA.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.Protein Conformation: 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).Peptide Chain Initiation, Translational: A process of GENETIC TRANSLATION whereby the formation of a peptide chain is started. It includes assembly of the RIBOSOME components, the MESSENGER RNA coding for the polypeptide to be made, INITIATOR TRNA, and PEPTIDE INITIATION FACTORS; and placement of the first amino acid in the peptide chain. The details and components of this process are unique for prokaryotic protein biosynthesis and eukaryotic protein biosynthesis.Nucleic Acid Denaturation: Disruption of the secondary structure of nucleic acids by heat, extreme pH or chemical treatment. Double strand DNA is "melted" by dissociation of the non-covalent hydrogen bonds and hydrophobic interactions. Denatured DNA appears to be a single-stranded flexible structure. The effects of denaturation on RNA are similar though less pronounced and largely reversible.Base Composition: The relative amounts of the PURINES and PYRIMIDINES in a nucleic acid.Threonine: An essential amino acid occurring naturally in the L-form, which is the active form. It is found in eggs, milk, gelatin, and other proteins.Spermine: A biogenic polyamine formed from spermidine. It is found in a wide variety of organisms and tissues and is an essential growth factor in some bacteria. It is found as a polycation at all pH values. Spermine is associated with nucleic acids, particularly in viruses, and is thought to stabilize the helical structure.Thermodynamics: A rigorously mathematical analysis of energy relationships (heat, work, temperature, and equilibrium). It describes systems whose states are determined by thermal parameters, such as temperature, in addition to mechanical and electromagnetic parameters. (From Hawley's Condensed Chemical Dictionary, 12th ed)Bacterial Proteins: Proteins found in any species of bacterium.RNA, Viral: Ribonucleic acid that makes up the genetic material of viruses.Electrophoresis, Polyacrylamide Gel: Electrophoresis in which a polyacrylamide gel is used as the diffusion medium.Adenosine: A nucleoside that is composed of ADENINE and D-RIBOSE. Adenosine or adenosine derivatives play many important biological roles in addition to being components of DNA and RNA. Adenosine itself is a neurotransmitter.Bacillus subtilis: A species of gram-positive bacteria that is a common soil and water saprophyte.Deoxyribonucleotides: A purine or pyrimidine base bonded to a DEOXYRIBOSE containing a bond to a phosphate group.Chromatography: Techniques used to separate mixtures of substances based on differences in the relative affinities of the substances for mobile and stationary phases. A mobile phase (fluid or gas) passes through a column containing a stationary phase of porous solid or liquid coated on a solid support. Usage is both analytical for small amounts and preparative for bulk amounts.UracilPlasmids: 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.Cell-Free System: A fractionated cell extract that maintains a biological function. A subcellular fraction isolated by ultracentrifugation or other separation techniques must first be isolated so that a process can be studied free from all of the complex side reactions that occur in a cell. The cell-free system is therefore widely used in cell biology. (From Alberts et al., Molecular Biology of the Cell, 2d ed, p166)Serine: A non-essential amino acid occurring in natural form as the L-isomer. It is synthesized from GLYCINE or THREONINE. It is involved in the biosynthesis of PURINES; PYRIMIDINES; and other amino acids.Ribonucleases: Enzymes that catalyze the hydrolysis of ester bonds within RNA. EC 3.1.-.Transcription, Genetic: The biosynthesis of RNA carried out on a template of DNA. The biosynthesis of DNA from an RNA template is called REVERSE TRANSCRIPTION.Conserved Sequence: 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.Adenine: A purine base and a fundamental unit of ADENINE NUCLEOTIDES.Histidine: An essential amino acid that is required for the production of HISTAMINE.Stereoisomerism: The phenomenon whereby compounds whose molecules have the same number and kind of atoms and the same atomic arrangement, but differ in their spatial relationships. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 5th ed)Macromolecular Substances: 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.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)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.Escherichia coli Proteins: Proteins obtained from ESCHERICHIA COLI.RNA-Binding Proteins: Proteins that bind to RNA molecules. Included here are RIBONUCLEOPROTEINS and other proteins whose function is to bind specifically to RNA.Binding, Competitive: The interaction of two or more substrates or ligands with the same binding site. The displacement of one by the other is used in quantitative and selective affinity measurements.