Laalami S, Putzer H, Plumbridge J A, Grunberg-Manago M
Institut de Biologie Physico-Chimique, URA 1139, Paris, France.
J Mol Biol. 1991 Jul 20;220(2):335-49. doi: 10.1016/0022-2836(91)90017-z.
We have constructed strains carrying null mutations in the chromosomal copy of the gene for translational initiation factor (IF) 2 (infB). A functional copy of the infB gene is supplied in trans by a thermosensitive lysogenic lambda phage integrated at att lambda. These strains enabled us to test in vivo the importance of different structural elements of IF2 expressed from genetically engineered plasmid constructs. We found that, as expected, the gene for IF2 is essential. However, a protein consisting of the C-terminal 55,000 Mr fragment of the wild-type IF2 protein is sufficient to allow growth when supplied in excess. This result suggests that the catalytic properties are localized in the C-terminal half of the protein, which includes the G-domain, and that this fragment is sufficient to complement the IF2 deficiency in the infB deletion strain.
我们构建了在翻译起始因子（IF）2（infB）基因的染色体拷贝中携带无效突变的菌株。infB基因的功能拷贝由整合在att λ处的温度敏感溶原性λ噬菌体反式提供。这些菌株使我们能够在体内测试从基因工程质粒构建体表达的IF2不同结构元件的重要性。我们发现，正如预期的那样，IF2基因是必需的。然而，当过量提供时，由野生型IF2蛋白的C末端55,000 Mr片段组成的蛋白质足以支持生长。这一结果表明，催化特性定位于该蛋白质的C末端一半，其中包括G结构域，并且该片段足以补充infB缺失菌株中的IF2缺陷。
