Biomaterial Database

Studies on the binding of acylaminoacyl-tRNA to rat liver 60S ribosomal subunits and its participation in the peptidyltransferase reaction. 1975

B Edens, and H A Thompson, and K Moldave

Peptidyltransferase with rat liver 60S subunits can be measured by the reaction between exogenous acylaminoacyl-tRNA and puromycin to form acylaminoacylpuromycin in the presence of 33% methanol, 0.3 M KCl, and 4 mM MgCl2. An assay system has been developed that allows examination of the binding of acetylphenylalanyl-tRNA to the ribosomal subunit "P" site, the transpeptidation of the 60S-bound substrate to puromycin, and the requirements for these individual steps. Binding of acetylphenylalanyl-tRNA to 60S subunits is stimulated several-fold by the addition of methanol, but the extent of binding in alcohol is the same in 60 as in 300 mM KCl containing solutions. Formation of acetylphenylalanyl-puromycin from 60S-acetylphenylalanyl-tRNA complex and puromycin stringently requires alcohol and the initial rate of the reaction is markedly greater at 300 mM KCl than at 60 mM KCl concentrations. Thus, alcohol and high concentrations of monovalent cation affect the reaction of an event subsequent to the binding of substrate to the "P" site. Preincubation of 60S subunits with poly(U), which stimulates the overall peptidyltransferase reaction, does not affect the amount of acetylphenylalanyl-tRNA that is bound to the particles; however, it markedly stimulates the initial rate of the transpeptidation reaction between 60S-acetylphenylalanyl-tRNA complex and puromycin. The codon specificity and the failure to affect binding with poly(U) suggest a role for the polynucleotide in the alignment or stabilization of the acylaminoacyl-tRNA on the "P" site rather than an effect on binding to either of the two particle sites or on the peptidyltransferase "active center." The effect of 40S subunits, which inhibit the overall peptidyltransferase reaction, on the binding of substrate could not be clearly interpreted since all three preparations, 60S subunits, 40S subunits, and combinations of 60S plus 40S particles, appear to bind acetylphenylalanyl-tRNA in the presence of methanol. However, the initial rate of peptide bond formation is several times greater with 60S-acetylphenylalanyl-tRNA complex than with 60S plus 40S particles containing bound acetylphenylalanyl-tRNA and the addition of 40S subunits to preformed 60S-acetylphenylalanyl-tRNA complex during the transpeptidation phase of the reaction in methanol does not affect the rate of peptide bond formation. Thus, 40S subunits seem to inhibit peptidyltransferase by forming less reactive particles in aqueous solutions. Contd.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008099	Liver	A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances.	Livers
D010455	Peptides	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 considered to be larger versions of peptides that can form into complex structures such as ENZYMES and RECEPTORS.	Peptide,Polypeptide,Polypeptides
D011485	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.	Plasma Protein Binding Capacity,Binding, Protein
D011955	Receptors, Drug	Proteins that bind specific drugs with high affinity and trigger intracellular changes influencing the behavior of cells. Drug receptors are generally thought to be receptors for some endogenous substance not otherwise specified.	Drug Receptors,Drug Receptor,Receptor, Drug
D000217	Acyltransferases	Enzymes from the transferase class that catalyze the transfer of acyl groups from donor to acceptor, forming either esters or amides. (From Enzyme Nomenclature 1992) EC 2.3.	Acyltransferase
D000432	Methanol	A colorless, flammable liquid used in the manufacture of FORMALDEHYDE and ACETIC ACID, in chemical synthesis, antifreeze, and as a solvent. Ingestion of methanol is toxic and may cause blindness.	Alcohol, Methyl,Carbinol,Sodium Methoxide,Wood Alcohol,Alcohol, Wood,Methoxide, Sodium,Methyl Alcohol
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D012270	Ribosomes	Multicomponent ribonucleoprotein structures found in the CYTOPLASM of all cells, and in MITOCHONDRIA, and PLASTIDS. They function in PROTEIN BIOSYNTHESIS via GENETIC TRANSLATION.	Ribosome
D012343	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.	Suppressor Transfer RNA,Transfer RNA,tRNA,RNA, Transfer, Suppressor,Transfer RNA, Suppressor,RNA, Suppressor Transfer