New insights into the enzymatic role of EF-G in ribosome recycling.
New insights into the enzymatic role of EF-G in ribosome recycling.
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关于 EF-G 在核糖体回收中酶作用的新见解
DOI：
10.1093/nar/gkv995
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发表时间：
2015-12-02
影响因子：
14.9
通讯作者：
Qin Y
中科院分区：
文献类型：
--
作者：
Zhang D;Yan K;Zhang Y;Liu G;Cao X;Song G;Xie Q;Gao N;Qin Y
在翻译过程中，延伸因子G（EF-G）在tRNA转位中起催化作用，在核糖体循环中起促进作用。EF-G通过稳定旋转的核糖体并与核糖体再循环因子（RRF）相互作用，诱导RRF的结构域旋转，进而分裂主要的亚基间桥，从而将核糖体分离成亚基进行再循环。本文采用系统突变、FRET分析和cryo-EM单颗粒方法，分析了EF-G/RRF与后终止复合物（PoTC）之间的相互作用。我们的数据显示，在EF-G结构域IV的尖端区域的两个保守的环（环I和II）具有不同的作用，在tRNA易位和核糖体回收。具体而言，环II可能直接参与破坏PoTC中螺旋44（来自30 S亚基的h44）和螺旋69（来自50 S亚基的H69）之间的主要亚基间桥B2 a。因此，我们的数据表明一种新的核糖体回收机制，需要EF-G的积极参与。除了支持RRF之外，EF-G还通过其环II在使B2 a不稳定中发挥酶促作用。
During translation, elongation factor G (EF-G) plays a catalytic role in tRNA translocation and a facilitative role in ribosome recycling. By stabilizing the rotated ribosome and interacting with ribosome recycling factor (RRF), EF-G was hypothesized to induce the domain rotations of RRF, which subsequently performs the function of splitting the major intersubunit bridges and thus separates the ribosome into subunits for recycling. Here, with systematic mutagenesis, FRET analysis and cryo-EM single particle approach, we analyzed the interplay between EF-G/RRF and post termination complex (PoTC). Our data reveal that the two conserved loops (loop I and II) at the tip region of EF-G domain IV possess distinct roles in tRNA translocation and ribosome recycling. Specifically, loop II might be directly involved in disrupting the main intersubunit bridge B2a between helix 44 (h44 from the 30S subunit) and helix 69 (H69 from the 50S subunit) in PoTC. Therefore, our data suggest a new ribosome recycling mechanism which requires an active involvement of EF-G. In addition to supporting RRF, EF-G plays an enzymatic role in destabilizing B2a via its loop II.