SecM-stalled ribosomes adopt an altered geometry at the peptidyl transferase center.
SecM-stalled ribosomes adopt an altered geometry at the peptidyl transferase center.
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DOI：
10.1371/journal.pbio.1000581
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发表时间：
2011-01-18
期刊：
影响因子：
9.8
通讯作者：
Beckmann R
中科院分区：
文献类型：
--
作者：
Bhushan S;Hoffmann T;Seidelt B;Frauenfeld J;Mielke T;Berninghausen O;Wilson DN;Beckmann R
核糖体的结构在SecM肽的翻译过程中停滞，提供了对大亚基活性位点失活的机制的深入了解。当新生多肽链合成时，它们通过核糖体大亚基中的隧道。特定的新生链和核糖体隧道之间的相互作用被用来诱导基因表达调控的翻译停滞。一个充分表征的实例是大肠杆菌SecM（分泌监测器）基因产物，其诱导停滞以上调下游secA基因的翻译起始，这是蛋白质输出所需的。虽然许多SecM和核糖体隧道的关键组成部分已被确定，了解的机制，其中的肽基转移酶中心的核糖体被灭活一直缺乏。在这里，我们提出了一个冷冻电子显微镜重建的SecM停滞的核糖体新生链复合物在5.6 ℃。虽然没有级联的rRNA构象变化是明显的，这种结构揭示了SecM和核糖体隧道的关键残基之间的直接相互作用。此外，转移的位置的tRNA新生肽键的SecM-tRNA提供了一个理由，肽基转移酶中心沉默，条件是同时存在的一个Pro-tRNAPro在核糖体的A位点。这些结果表明，一个独特的变构机制，调节翻译延长的SecM失速肽。在所有细胞中，核糖体都负责制造蛋白质。当蛋白质合成时，它们通过核糖体中的隧道，一些生长的蛋白质与隧道相互作用，导致蛋白质合成停滞。在这里，我们使用冷冻电子显微镜，以确定在大肠杆菌分泌监控（SecM）多肽链的翻译过程中停滞的核糖体的结构。该结构揭示了SecM肽通过隧道的路径以及与隧道组分相互作用的位点。有趣的是，结构显示转移RNA（tRNA）的位置发生了变化，生长中的SecM多肽链与之相连。由于蛋白质合成过程中的肽键形成需要精确放置底物，即肽基-tRNA和传入的氨基酰基-tRNA，因此提出SecM-tRNA的这种转变解释了为什么不能发生肽键形成和翻译停滞。
A structure of a ribosome stalled during translation of the SecM peptide provides insight into the mechanism by which the large subunit active site is inactivated. As nascent polypeptide chains are synthesized, they pass through a tunnel in the large ribosomal subunit. Interaction between specific nascent chains and the ribosomal tunnel is used to induce translational stalling for the regulation of gene expression. One well-characterized example is the Escherichia coli SecM (secretion monitor) gene product, which induces stalling to up-regulate translation initiation of the downstream secA gene, which is needed for protein export. Although many of the key components of SecM and the ribosomal tunnel have been identified, understanding of the mechanism by which the peptidyl transferase center of the ribosome is inactivated has been lacking. Here we present a cryo-electron microscopy reconstruction of a SecM-stalled ribosome nascent chain complex at 5.6 Å. While no cascade of rRNA conformational changes is evident, this structure reveals the direct interaction between critical residues of SecM and the ribosomal tunnel. Moreover, a shift in the position of the tRNA–nascent peptide linkage of the SecM-tRNA provides a rationale for peptidyl transferase center silencing, conditional on the simultaneous presence of a Pro-tRNAPro in the ribosomal A-site. These results suggest a distinct allosteric mechanism of regulating translational elongation by the SecM stalling peptide. In all cells, ribosomes perform the job of making proteins. As the proteins are synthesized they pass through a tunnel in the ribosome, and some growing proteins interact with the tunnel, leading to stalling of protein synthesis. Here, we used cryo-electron microscopy to determine the structure of a ribosome stalled during the translation of the Escherichia coli secretion monitor (SecM) polypeptide chain. The structure reveals the path of the SecM peptide through the tunnel as well as the sites of interaction with the tunnel components. Interestingly, the structure shows a shift in the position of the transfer RNA (tRNA) to which the growing SecM polypeptide chain is attached. Since peptide bond formation during protein synthesis requires precise placement of the substrates, namely, the peptidyl-tRNA and the incoming amino acyl-tRNA, it is proposed that this shift in the SecM-tRNA explains why peptide bond formation cannot occur and translation stalls.
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DOI：
10.1016/j.bbrc.2010.01.073
发表时间：
2010-02-26
影响因子：
3.1
作者：
Ito, Koreaki;Chiba, Shinobu;Pogliano, Kit
通讯作者：
Pogliano, Kit
DOI：
10.1107/s0907444904019158
发表时间：
2004-12-01
影响因子：
2.2
作者：
Emsley, P;Cowtan, K
通讯作者：
Cowtan, K
DOI：
10.1073/pnas.172404099
发表时间：
2002-09-03
影响因子：
11.1
作者：
Hansen, JL;Schmeing, TM;Steitz, TA
通讯作者：
Steitz, TA
影响因子：
3.2
作者：
Lawrence, Marlon G.;Lindahl, Lasse;Zengel, Janice M.
通讯作者：
Zengel, Janice M.
影响因子：
16
作者：
Cruz-Vera, LR;Rajagopal, S;Yanofsky, C
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Yanofsky, C