Pallesen Jesper, Hashem Yaser, Korkmaz Gürkan, Koripella Ravi Kiran, Huang Chenhui, Ehrenberg Måns, Sanyal Suparna, Frank Joachim
Department of Biochemistry and Molecular Biophysics , Howard Hughes Medical Institute, Columbia University , New York City , United States.
Elife. 2013 Jun 4;2:e00411. doi: 10.7554/eLife.00411.
Termination of messenger RNA translation in Bacteria and Archaea is initiated by release factors (RFs) 1 or 2 recognizing a stop codon in the ribosomal A site and releasing the peptide from the P-site transfer RNA. After release, RF-dissociation is facilitated by the G-protein RF3. Structures of ribosomal complexes with RF1 or RF2 alone or with RF3 alone-RF3 bound to a non-hydrolyzable GTP-analog-have been reported. Here, we present the cryo-EM structure of a post-termination ribosome containing both apo-RF3 and RF1. The conformation of RF3 is distinct from those of free RF3•GDP and ribosome-bound RF3•GDP(C/N)P. Furthermore, the conformation of RF1 differs from those observed in RF3-lacking ribosomal complexes. Our study provides structural keys to the mechanism of guanine nucleotide exchange on RF3 and to an L12-mediated ribosomal recruitment of RF3. In conjunction with previous observations, our data provide the foundation to structurally characterize the complete action cycle of the G-protein RF3. DOI:http://dx.doi.org/10.7554/eLife.00411.001.
在细菌和古生菌中，信使核糖核酸（mRNA）翻译的终止由释放因子（RF）1或2启动，它们识别核糖体A位点的终止密码子，并从P位点转运核糖核酸（tRNA）上释放肽链。释放后，G蛋白RF3促进RF的解离。已报道了核糖体复合物与单独的RF1或RF2或与单独的RF3（RF3与不可水解的GTP类似物结合）的结构。在此，我们展示了包含脱辅基RF3和RF1的终止后核糖体的冷冻电镜结构。RF3的构象不同于游离的RF3•GDP和核糖体结合的RF3•GDP(C/N)P的构象。此外，RF1的构象不同于在缺乏RF3的核糖体复合物中观察到的构象。我们的研究为RF3上鸟嘌呤核苷酸交换机制以及L12介导的RF3核糖体募集提供了结构关键。结合先前的观察结果，我们的数据为从结构上表征G蛋白RF3的完整作用循环奠定了基础。DOI:http://dx.doi.org/10.7554/eLife.00411.001
