Center for Molecular Biology of RNA and Department of Molecular, Cell and Developmental Biology, University of California at Santa Cruz, Santa Cruz, CA 95064, USA.
Science. 2014 Sep 5;345(6201):1188-91. doi: 10.1126/science.1255030.
Coupled translocation of messenger RNA and transfer RNA (tRNA) through the ribosome, a process catalyzed by elongation factor EF-G, is a crucial step in protein synthesis. The crystal structure of a bacterial translocation complex describes the binding states of two tRNAs trapped in mid-translocation. The deacylated P-site tRNA has moved into a partly translocated pe/E chimeric hybrid state. The anticodon stem-loop of the A-site tRNA is captured in transition toward the 30S P site, while its 3' acceptor end contacts both the A and P loops of the 50S subunit, forming an ap/ap chimeric hybrid state. The structure shows how features of ribosomal RNA rearrange to hand off the A-site tRNA to the P site, revealing an active role for ribosomal RNA in the translocation process.
核糖体中介导信使 RNA 和转移 RNA（tRNA）的偶联转位，这一过程由延伸因子 EF-G 催化，是蛋白质合成的关键步骤。一个细菌转位复合物的晶体结构描述了两个被捕获在转位过程中间的 tRNA 的结合状态。去酰化的 P 位 tRNA 已进入部分转位的 pe/E 嵌合混合状态。A 位 tRNA 的反密码子茎环被捕获在向 30S P 位转变的过程中，而其 3' 受体末端与 50S 亚基的 A 环和 P 环都接触，形成 ap/ap 嵌合混合状态。该结构显示了核糖体 RNA 如何通过重排来将 A 位 tRNA 递送至 P 位，揭示了核糖体 RNA 在转位过程中的活跃作用。
