Structural Basis for Polyproline-Mediated Ribosome Stalling and Rescue by the Translation Elongation Factor EF-P
Structural Basis for Polyproline-Mediated Ribosome Stalling and Rescue by the Translation Elongation Factor EF-P
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DOI：
10.1016/j.molcel.2017.10.014
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发表时间：
2017-11-02
期刊：
影响因子：
16
通讯作者：
Wilson, Daniel N.
中科院分区：
文献类型：
--
作者：
Huter, Paul;Arenz, Stefan;Wilson, Daniel N.
核糖体合成含有连续脯氨酸残基的蛋白质变得停滞，需要通过独特修饰的翻译延伸因子（细菌中的EF-P）或古细菌/真核生物a/eIF5A的作用进行拯救。到目前为止，没有EF-P或eIF5A的结构与翻译核糖体在多聚脯氨酸延伸处停滞的复合物，因此缺乏对EF-P/eIF5A如何拯救这些停滞的核糖体的结构洞察。在这里，我们提出了冷冻EM结构的核糖体停滞在脯氨酸伸展，没有和修改EF-P。结构表明，有利的构象的聚脯氨酸含有新生链是不兼容的肽出口隧道的核糖体，并导致不稳定的peptidyltRNA。EF-P的结合稳定了P位点tRNA，特别是通过其修饰和CCA末端之间的相互作用，从而加强了含聚脯氨酸的新生链的替代构象，这允许有利于肽键形成的底物几何形状。
Ribosomes synthesizing proteins containing consecutive proline residues become stalled and require rescue via the action of uniquely modified translation elongation factors, EF-P in bacteria, or archaeal/eukaryotic a/eIF5A. To date, no structures exist of EF-P or eIF5A in complex with translating ribosomes stalled at polyproline stretches, and thus structural insight into how EF-P/eIF5A rescue these arrested ribosomes has been lacking. Here we present cryo-EM structures of ribosomes stalled on proline stretches, without and with modified EF-P. The structures suggest that the favored conformation of the polyproline-containing nascent chain is incompatible with the peptide exit tunnel of the ribosome and leads to destabilization of the peptidyltRNA. Binding of EF-P stabilizes the P-site tRNA, particularly via interactions between its modification and the CCA end, thereby enforcing an alternative conformation of the polyproline-containing nascent chain, which allows a favorable substrate geometry for peptide bond formation.