tmRNA-SmpB complex mimics native aminoacyl-tRNAs in the A site of stalled ribosomes
tmRNA-SmpB complex mimics native aminoacyl-tRNAs in the A site of stalled ribosomes
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DOI：
10.1016/j.jsb.2009.10.015
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发表时间：
2010-03-01
影响因子：
3
通讯作者：
Lindahl, Martin
中科院分区：
文献类型：
--
作者：
Cheng, Kimberley;Ivanova, Natalia;Lindahl, Martin
细菌核糖体在错误的、经常被截断的、缺少终止密码子的mRNAs上停滞不前，可以通过反式翻译来挽救。它依赖于一种RNA分子(TmRNA)，能够用自己的开放阅读框架(ORF)取代有缺陷的mRNA。TmRNAORF的翻译会导致错误蛋白的标记，以便降解并从核糖体中释放出来。我们用单颗粒冷冻电子显微镜观察了在延伸因子Tu(EF-Tu)上GTP水解后的70年代大肠杆菌核糖体上tmRNA及其辅助蛋白SmpB的情况。三维重建和异质性分析得到了位于核糖体A位的tmRNA-SmpB复合体的15A分辨率结构，这表明SmpB模拟了tRNA的tRNA样结构域中缺失的天然tRNA的反密码子和D茎。我们得出结论，在蛋白质伸长过程中，tmRNA-SmpB复合体非常像氨基酰-tRNA一样适应于核糖体A位。(C)2009 Elsevier Inc.保留所有权利。
Bacterial ribosomes stalled on faulty, often truncated, mRNAs lacking stop codons are rescued by trans-translation. It relies on an RNA molecule (tmRNA) capable of replacing the faulty mRNA with its own open reading frame (ORF). Translation of tmRNA ORF results in the tagging of faulty protein for degradation and its release from the ribosome. We used single-particle cryo-electron microscopy to visualize tmRNA together with its helper protein SmpB on the 70S Escherichia coli ribosome in states subsequent to GTP hydrolysis on elongation factor Tu (EF-Tu). Three-dimensional reconstruction and heterogeneity analysis resulted in a 15 A resolution structure of the tmRNA-SmpB complex accommodated in the A site of the ribosome, which shows that SmpB mimics the anticodon- and D-stem of native tRNAs missing in the tRNA-like domain of tmRNA. We conclude that the tmRNA-SmpB complex accommodates in the ribosomal A site very much like an aminoacyl-tRNA during protein elongation. (C) 2009 Elsevier Inc. All rights reserved.