Ribosome hijacking: a role for small protein B during trans-translation
Ribosome hijacking: a role for small protein B during trans-translation
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DOI：
10.1038/embor.2008.243
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发表时间：
2009-02-01
期刊：
影响因子：
7.7
通讯作者：
Felden, Brice
中科院分区：
文献类型：
--
作者：
Nonin-Lecomte, Sylvie;Germain-Amiot, Noella;Felden, Brice
核糖体对密码子-反密码子配对的严格识别确保了蛋白质合成的准确性和保真度。在真细菌中，翻译监测和核糖体拯救是通过‘tmRNA-SmpB’系统(转移信使RNA-小蛋白B)执行的。值得注意的是，在没有密码子-反密码子相互作用的情况下，氨酰化tmRNA进入和适应停滞的核糖体，而是在SmpB存在的情况下。在这里，我们证明了在一个停滞的核糖体中，SmpB与三个普遍保守的碱基G530、A1492和A1493相互作用，形成30S亚单位解码中心，在这个中心发生典型的密码子反密码子配对。通过核磁共振鉴定了一个小的解码中心的A1492和A1493位置的足迹，以及一组保守的SmpB氨基酸上的足迹。这些残基上的突变体表现出与Delta smpB菌株相同的生长缺陷。SmpB蛋白与启动因子1在功能和结构上都有相似之处，被认为是密码子和反密码子之间配对的功能模拟。
Tight recognition of codon-anticodon pairings by the ribosome ensures the accuracy and fidelity of protein synthesis. In eubacteria, translational surveillance and ribosome rescue are performed by the 'tmRNA-SmpB' system (transfer messenger RNA-small protein B). Remarkably, entry and accommodation of aminoacylated-tmRNA into stalled ribosomes occur without a codon-anticodon interaction but in the presence of SmpB. Here, we show that within a stalled ribosome, SmpB interacts with the three universally conserved bases G530, A1492 and A1493 that form the 30S subunit decoding centre, in which canonical codon anticodon pairing occurs. The footprints at positions A1492 and A1493 of a small decoding centre, as well as on a set of conserved SmpB amino acids, were identified by nuclear magnetic resonance. Mutants at these residues display the same growth defects as for Delta smpB strains. The SmpB protein has functional and structural similarities with initiation factor 1, and is proposed to be a functional mimic of the pairing between a codon and an anticodon.