Initiation factors IF1 and IF2 synergistically remove peptidyl-tRNAs with short polypeptides from the P-site of translating Escherichia coli ribosomes
Initiation factors IF1 and IF2 synergistically remove peptidyl-tRNAs with short polypeptides from the P-site of translating Escherichia coli ribosomes
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DOI：
10.1006/jmbi.1998.1953
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发表时间：
1998-08-14
影响因子：
5.6
通讯作者：
Ehrenberg, M
中科院分区：
文献类型：
--
作者：
Karimi, R;Pavlov, MY;Ehrenberg, M
起始因子IF 1和IF 2在大肠杆菌翻译中的一个新功能已被鉴定。结果表明，这些因子有效地催化肽基-tRNA与不同长度的多肽从E.大肠杆菌核糖体，这两个因素的同时存在是诱导脱落所必需的。因子诱导的脱落发生在A位点的有义密码子和终止密码子中，并与肽的延伸或终止竞争。IF 1和IF 2催化脱落的效率随着新生多肽长度的增加而降低，但对于所研究的最长多肽链七肽基-tRNA来说非常显着。在不存在IF 1和IF 2的情况下，对于不同的肽基-tRNA，下降的速率变化很大，并且取决于新生肽的长度和序列。有效的因子催化的下降需要GTP，但不是GTP水解，如在实验中所示，没有鸟嘌呤核苷酸，GDP或与不可裂解的类似物GMP-PNP。同时过表达的IF 1和IF 2在体内抑制细胞生长，特别是在一些肽基-tRNA水解酶缺陷的突变体，这表明起始因子催化的下降肽基-tRNA可以发生在一个显着的规模在细菌细胞。这种以前未知的功能IF 1和IF 2的细菌生理学的后果进行了讨论。(C)北京：科学出版社.
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 noncleavable 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. (C) 1998 Academic Press.