PMID:9698545
| Citation |
Karimi, R, Pavlov, MY, Heurgué-Hamard, V, Buckingham, RH and Ehrenberg, M (1998) Initiation factors IF1 and IF2 synergistically remove peptidyl-tRNAs with short polypeptides from the P-site of translating Escherichia coli ribosomes. J. Mol. Biol. 281:241-52 |
|---|---|
| Abstract |
A novel function of initiation factors IF1 and IF2 in Escherichia coli translation has been identified. It is shown that these factors efficiently catalyse dissociation of peptidyl-tRNAs with polypeptides of different length from the P-site of E. coli ribosomes, and that the simultaneous presence of both factors is required for induction of drop-off. The factor-induced drop-off occurs with both sense and stop codons in the A-site and competes with peptide elongation or termination. The efficiency with which IF1 and IF2 catalyse drop-off decreases with increasing length of the nascent polypeptide, but is quite significant for hepta-peptidyl-tRNAs, the longest polypeptide chains studied. In the absence of IF1 and IF2 the rate of drop-off varies considerably for different peptidyl-tRNAs, and depends both on the length and sequence of the nascent peptide. Efficient factor-catalysed drop-off requires GTP but not GTP hydrolysis, as shown in experiments without guanine nucleotides, with GDP or with the non-cleavable analogue GMP-PNP.Simultaneous overexpression of IF1 and IF2 in vivo inhibits cell growth specifically in some peptidyl-tRNA hydrolase deficient mutants, suggesting that initiation factor-catalysed drop-off of peptidyl-tRNA can occur on a significant scale in the bacterial cell. Consequences for the bacterial physiology of this previously unknown function of IF1 and IF2 are discussed. |
| Links |
PubMed Online version:10.1006/jmbi.1998.1953 |
| Keywords |
Carboxylic Ester Hydrolases/metabolism; Escherichia coli/genetics; Escherichia coli/growth & development; Guanosine Triphosphate/physiology; Oligopeptides/metabolism; Peptide Initiation Factors/metabolism; Peptide Initiation Factors/pharmacology; Prokaryotic Initiation Factor-2; Protein Biosynthesis/physiology; RNA, Transfer, Amino Acyl/metabolism; RNA, Transfer, Met/metabolism; Ribosomes/metabolism |
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