tRNA Translocation by the Eukaryotic 80S Ribosome and the Impact of GTP Hydrolysis
tRNA Translocation by the Eukaryotic 80S Ribosome and the Impact of GTP Hydrolysis
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DOI：
10.1016/j.celrep.2018.11.040
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发表时间：
2018-12-04
期刊：
影响因子：
8.8
通讯作者：
Budkevich, Tatyana V.
中科院分区：
文献类型：
--
作者：
Flis, Julia;Holm, Mikael;Budkevich, Tatyana V.
易位使trna2mrna模块在蛋白质合成的延伸阶段定向穿过核糖体。虽然已知易位会在核糖体和tRNA底物中引起大的构象变化，但确保蛋白质合成机制这一关键方面的速度和保真度的精心安排的事件尚未完全阐明。在这里，我们展示了哺乳动物核糖体上易位中间体的三种高分辨率结构，与细菌不同，含有易位酶eEF2和完整tRNA2 mRNA模块的核糖体复合物被不可水解的GTP类似物GMPPNP捕获。与观察到的结构一致，单分子成像显示GTP水解主要促进了速率限制，即易位的最后步骤，这是因子解离所必需的，并且在细菌和哺乳动物系统中由E位点的deacyl-tRNA解离速率不同地调节。
Translocation moves the tRNA2, mRNA module directionally through the ribosome during the elongation phase of protein synthesis. Although translocation is known to entail large conformational changes within both the ribosome and tRNA substrates, the orchestrated events that ensure the speed and fidelity of this critical aspect of the protein synthesis mechanism have not been fully elucidated. Here, we present three high-resolution structures of intermediates of translocation on the mammalian ribosome where, in contrast to bacteria, ribosomal complexes containing the translocase eEF2 and the complete tRNA2, mRNA module are trapped by the non-hydrolyzable GTP analog GMPPNP. Consistent with the observed structures, single-molecule imaging revealed that GTP hydrolysis principally facilitates rate-limiting, final steps of translocation, which are required for factor dissociation and which are differentially regulated in bacterial and mammalian systems by the rates of deacyl-tRNA dissociation from the E site.