Reverse translocation of tRNA in the ribosome
Reverse translocation of tRNA in the ribosome
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DOI：
10.1016/j.molcel.2006.11.025
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发表时间：
2006-12-28
期刊：
影响因子：
16
通讯作者：
Fredrick, Kurt
中科院分区：
文献类型：
--
作者：
Shoji, Shinichiro;Walker, Sarah E.;Fredrick, Kurt
一种广泛持有的观点是，核糖体中tRNA的方向运动是由内在机制决定的，并由转肽作用在热力学上驱动。在这里，我们表明，在某些核糖体复合物中，前易位（PRE）状态在遗传学上优于后易位（POST）状态。当EF-G从处于POST状态的核糖体中耗尽时，或者当tRNA被添加到含有P-位点tRNA的核糖体的E位点时，观察到从POST到PRE状态的自发和有效的转化。在后一种测定中，tRNA移动的速率被链霉素和新霉素增加，被四环素降低，并且不受tRNA的酰化状态的影响。在一种情况下，我们提供的证据表明，复杂的转换发生的反向易位（即，分别将tRNA从E和P位点直接移动到P和A位点）。这些发现对易位的能量学具有重要意义。
A widely held view is that directional movement of tRNA in the ribosome is determined by an intrinsic mechanism and driven thermodynamically by transpeptidation. Here, we show that, in certain ribosomal complexes, the pretranslocation (PRE) state is thermodynamically favored over the posttranslocation (POST) state. Spontaneous and efficient conversion from the POST to PRE state is observed when EF-G is depleted from ribosomes in the POST state or when tRNA is added to the E site of ribosomes containing P-site tRNA. In the latter assay, the rate of tRNA movement is increased by streptomycin and neomycin, decreased by tetracycline, and not affected by the acylation state of the tRNA. In one case, we provide evidence that complex conversion occurs by reverse translocation (i.e., direct movement of the tRNAs from the E and P sites to the P and A sites, respectively). These findings have important implications for the energetics of translocation.