Das Gautam, Thotala Dinesh Kumar, Kapoor Suman, Karunanithi Sheelarani, Thakur Suman S, Singh N Sadananda, Varshney Umesh
Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, Karnataka, India.
EMBO J. 2008 Mar 19;27(6):840-51. doi: 10.1038/emboj.2008.20. Epub 2008 Feb 21.
Translation initiation from the ribosomal P-site is the specialty of the initiator tRNAs (tRNA(fMet)). Presence of the three consecutive G-C base pairs (G29-C41, G30-C40 and G31-C39) in their anticodon stems, a highly conserved feature of the initiator tRNAs across the three kingdoms of life, has been implicated in their preferential binding to the P-site. How this feature is exploited by ribosomes has remained unclear. Using a genetic screen, we have isolated an Escherichia coli strain, carrying a G122D mutation in folD, which allows initiation with the tRNA(fMet) containing mutations in one, two or all the three G-C base pairs. The strain shows a severe deficiency of methionine and S-adenosylmethionine, and lacks nucleoside methylations in rRNA. Targeted mutations in the methyltransferase genes have revealed a connection between the rRNA modifications and the fundamental process of the initiator tRNA selection by the ribosome.
从核糖体P位点起始翻译是起始tRNA（tRNA(fMet)）的特性。在其反密码子茎中存在三个连续的G-C碱基对（G29-C41、G30-C40和G31-C39），这是生命三界中起始tRNA的高度保守特征，与它们优先结合到P位点有关。核糖体如何利用这一特征仍不清楚。通过遗传筛选，我们分离出了一株大肠杆菌菌株，其folD基因携带G122D突变，该突变允许含有一个、两个或所有三个G-C碱基对突变的tRNA(fMet)起始翻译。该菌株表现出严重的甲硫氨酸和S-腺苷甲硫氨酸缺乏，并且rRNA中缺乏核苷甲基化。甲基转移酶基因的靶向突变揭示了rRNA修饰与核糖体选择起始tRNA的基本过程之间的联系。
