title: Enzymatic binding of aminoacyl transfer ribonucleic acid to ribosomes: the study of binding sites of 2' and 3' isomers of aminoacyl transfer ribonucleic acid.
abstract: The mechanism of enzymatic binding of AAtRNA to the acceptor site Escherichia coli ribosomes has been studied using the following aminoacyl oligonucleotides as models of the 3' terminus of AA-tRNA: C-A-Phe, C-A-(2'-Phe)H, and C-A(2'H)Phe. T-psi-C-Gp was used as a model of loop IV of tRNA. The EF-T dependent binding of Phe-tRNA to ribosomes (in the presence of either GTP or GMPPCP) and the GTPase activity associated with EF-T dependent binding of the Phe-tRNA were inhibited by C-A-Phe,C-A(2'Phe)H, and C-A(2'H)Phe. These aminoacyl oligonucleotides inhibit both the formation of ternary complex EF-Tu-GTP-AA-tRNA and the interaction of this complex with the ribosomal A site. The uncoupled EF-Tu dependent GTPase (in the absence of AA-tRNA) was also inhibited by C-A-Phe, C-A(2'Phe)H, and C-A(2'H)Phe, while nonenzymatic binding of Phe-tRNA to the ribosomal A site was inhibited by C-A-Phe and C-A(2'-Phe)H, but not by C-A(2'H)Phe. The tetranucleotide T-psi-C-Gp inhibited both enzyme binding of Phe-tRNA and EF-T dependent GTP hydrolysis. However, inhibition of the latter reaction occured at a lower concentration of T-psi-C-Gp suggesting a specific role of T-psi-C-Gp loop of AA-tRNA in the GTPase reaction. The role of the 2' and 3' isomers of AA-tRNA during enzymatic binding to ribosomes is discussed and it is suggested that 2' leads to 3' transacylation in AA-tRNA is a step which follows GTP hydrolysis but precedes peptide bond formation.
mesh_terms: D001665:Binding Sites; D001667:Binding, Competitive; D004926:Escherichia coli / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D007700:Kinetics; D009843:Oligoribonucleotides / Q000378:metabolism; D010441:Peptide Chain Elongation, Translational; D010445:Peptide Elongation Factors; D010649:Phenylalanine; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism; D011485:Protein Binding; D012270:Ribosomes / Q000378:metabolism*
chemical_list: D009843:Oligoribonucleotides; D010445:Peptide Elongation Factors; D010649:Phenylalanine; D006160:Guanosine Triphosphate; D010727:Phosphoric Diester Hydrolases