The role of translocation in ribosomal accuracy. Translocation rates for cognate and noncognate aminoacyl- and peptidyl-tRNAs on Escherichia coli ribosomes.
The ribosomal translocation, as measured in vitro by peptide formation on poly(U)-programmed Escherichia coli ribosomes in the presence of ternary complex, deacylated tRNA or N-acetyl-Phe-tRNA, and elongation factor G, is the rate-limiting step of protein synthesis. Elongation factor G stimulates the spontaneous translocation by a factor of about 500. N-Acetyl-Phe-Phe-tRNA(Phe E. coli) is translocated with a rate constant of 1-2 s-1 at 25 degrees C. Translocation of N-acetyl-Phe-Phe-tRNA(Phe yeast) and N-acetyl-Phe-Leu-tRNA(Leu E. coli) under identical conditions proceeds with a rate by about a factor of 2 and 10, respectively, more slowly. The translocation rate, therefore, is influenced by the nature of the tRNAs in the A-site. We can show, furthermore, that also the tRNA in the P-site, and presumably in the E-site as well, influences the rate of translocation. Reduced rates of translocation of noncognate peptidyl-tRNAs are accompanied by preferential dissociation of these tRNAs at the beginning of the translation of a mRNA.
Gast
F U
FU
Peters
F
F
Pingoud
A
A
D004926:Escherichia coli / Q000235:genetics; D020653:Peptide Elongation Factor G; D010445:Peptide Elongation Factors / Q000494:pharmacology; D010455:Peptides / Q000235:genetics*; D011072:Poly U / Q000378:metabolism; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism*; D012270:Ribosomes / Q000502:physiology*; D012441:Saccharomyces cerevisiae / Q000235:genetics; D014178:Translocation, Genetic
D020653:Peptide Elongation Factor G; D010445:Peptide Elongation Factors; D010455:Peptides; D012333:RNA, Messenger; D012346:RNA, Transfer, Amino Acyl; C006383:tRNA, N-acetylphenylalanine-; D011072:Poly U