title: The reaction of ribosomes with elongation factor Tu.GTP complexes. Aminoacyl-tRNA-independent reactions in the elongation cycle determine the accuracy of protein synthesis.
abstract: The fidelity of protein synthesis depends on the rate constants for the reaction of ribosomes with ternary complexes of elongation factor Tu (EF-Tu), GTP, and aminoacyl (aa)-tRNA. By measuring the rate constants for the reaction of poly(U)-programmed ribosomes with a binary complex of elongation factor (EF-Tu) and GTP we have shown that two of the key rate constants in the former reaction are determined exclusively by ribosome-EF-Tu interactions and are not affected by the aa-tRNA. These are the rate constant for GTP hydrolysis, which plays an important role in the fidelity of ternary complex selection by the ribosome, and the rate constant for EF-Tu.GDP dissociation from the ribosome, which plays an equally important role in subsequent proofreading of the aa-tRNA. We conclude that the fidelities of ternary complex selection and proofreading are fundamentally dependent on ribosome-EF-Tu interactions. These interactions determine the absolute value of the rate constants for GTP hydrolysis and EF-Tu.GDP dissociation. The ribosome then uses these rate constants as internal standards to measure, respectively, the rate constants for ternary complex and aa-tRNA dissociation from the ribosome. These rates, in turn, are highly dependent on whether the ternary complex and aa-tRNA are cognate or near-cognate to the codon being translated.
mesh_terms: D004926:Escherichia coli / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism*; D006868:Hydrolysis; D007700:Kinetics; D046911:Macromolecular Substances; D010444:Peptide Elongation Factor Tu / Q000378:metabolism*; D011072:Poly U / Q000378:metabolism; D014176:Protein Biosynthesis; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism*; D013873:Thionucleotides / Q000378:metabolism
chemical_list: D046911:Macromolecular Substances; D012346:RNA, Transfer, Amino Acyl; D013873:Thionucleotides; C006383:tRNA, N-acetylphenylalanine-; D011072:Poly U; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate; D010444:Peptide Elongation Factor Tu