转运RNA在核糖体中的反向易位。
Reverse translocation of tRNA in the ribosome.
作者信息
Shoji Shinichiro, Walker Sarah E, Fredrick Kurt
机构信息
Department of Microbiology, The Ohio State University, Columbus, Ohio 43210, USA.
出版信息
Mol Cell. 2006 Dec 28;24(6):931-42. doi: 10.1016/j.molcel.2006.11.025.
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.
一种广泛持有的观点是，tRNA在核糖体中的定向移动由一种内在机制决定，并通过转肽作用以热力学方式驱动。在这里，我们表明，在某些核糖体复合物中，转位前（PRE）状态在热力学上比转位后（POST）状态更有利。当从处于POST状态的核糖体中耗尽EF-G时，或者当将tRNA添加到含有P位点tRNA的核糖体的E位点时，会观察到从POST状态到PRE状态的自发且高效的转变。在后一种测定中，tRNA移动速率因链霉素和新霉素而增加，因四环素而降低，并且不受tRNA的酰化状态影响。在一种情况下，我们提供证据表明复合物转变是通过反向转位发生的（即，tRNA分别从E位点和P位点直接移动到P位点和A位点）。这些发现对转位的能量学具有重要意义。
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