Spontaneous reverse movement of mRNA-bound tRNA through the ribosome
Spontaneous reverse movement of mRNA-bound tRNA through the ribosome
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DOI：
10.1038/nsmb1221
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发表时间：
2007-04-01
影响因子：
16.8
通讯作者：
Rodnina, Marina V.
中科院分区：
文献类型：
--
作者：
Konevega, Andrey L.;Fischer, Niels;Rodnina, Marina V.
在蛋白质合成的易位步骤中，与信使RNA结合的两个转移RNA（tRNA-mRNA）的复合物穿过核糖体。该反应由细菌中称为EF-G的延伸因子促进，其由GTP水解提供动力，诱导核糖体的开放解锁构象，从而允许自发的tRNA-mRNA运动。在这里，我们表明，在EF-G的情况下，有自发向后运动，或retrotranslocation，两个tRNA结合mRNA。当同源E位点tRNA移动到P位点时，亲和力的增加驱动反向易位，这补偿了伴随肽基-tRNA从P位点移动到A位点的亲和力损失。这些结果支持转运过程中tRNA运动的扩散模型。在细胞中，tRNA的运动被EF-G偏向于向前的方向，EF-G起到布朗棘轮的作用，阻止tRNA向后运动。
During the translocation step of protein synthesis, a complex of two transfer RNAs bound to messenger RNA (tRNA-mRNA) moves through the ribosome. The reaction is promoted by an elongation factor, called EF-G in bacteria, which, powered by GTP hydrolysis, induces an open, unlocked conformation of the ribosome that allows for spontaneous tRNA-mRNA movement. Here we show that, in the absence of EF-G, there is spontaneous backward movement, or retrotranslocation, of two tRNAs bound to mRNA. Retrotranslocation is driven by the gain in affinity when a cognate E-site tRNA moves into the P site, which compensates the affinity loss accompanying the movement of peptidyl-tRNA from the P to the A site. These results lend support to the diffusion model of tRNA movement during translocation. In the cell, tRNA movement is biased in the forward direction by EF-G, which acts as a Brownian ratchet and prevents backward movement.