Center for Molecular Biology of RNA and Department of Molecular, Cell and Developmental Biology, University of California at Santa Cruz, CA 95064, USA.
RNA. 2012 Feb;18(2):230-40. doi: 10.1261/rna.031187.111. Epub 2011 Dec 20.
The class II release factor RF3 is a GTPase related to elongation factor EF-G, which catalyzes release of class I release factors RF1 and RF2 from the ribosome after termination of protein synthesis. The 3.3 Å crystal structure of the RF3·GDPNP·ribosome complex provides a high-resolution description of interactions and structural rearrangements that occur when binding of this translational GTPase induces large-scale rotational movements in the ribosome. RF3 induces a 7° rotation of the body and 14° rotation of the head of the 30S ribosomal subunit, and itself undergoes inter- and intradomain conformational rearrangements. We suggest that ordering of critical elements of switch loop I and the P loop, which help to form the GTPase catalytic site, are caused by interactions between the G domain of RF3 and the sarcin-ricin loop of 23S rRNA. The rotational movements in the ribosome induced by RF3, and its distinctly different binding orientation to the sarcin-ricin loop of 23S rRNA, raise interesting implications for the mechanism of action of EF-G in translocation.
RF3 是 II 类释放因子，与延伸因子 EF-G 相关，可催化蛋白质合成终止后核糖体上 I 类释放因子 RF1 和 RF2 的释放。RF3·GDPNP·核糖体复合物的 3.3 Å 晶体结构提供了一个高分辨率的描述，描述了当这种翻译 GTP 酶结合时，如何诱导核糖体发生大规模旋转运动，从而发生相互作用和结构重排。RF3 诱导 30S 核糖体亚基的主体旋转 7°，头部旋转 14°，自身经历了结构域间和结构域内的构象重排。我们认为，帮助形成 GTP 酶催化位点的开关环 I 和 P 环的关键元素的有序性是由 RF3 的 G 结构域与 23S rRNA 的 Sarcin-Ricin 环之间的相互作用引起的。RF3 诱导的核糖体旋转，以及其与 23S rRNA 的 Sarcin-Ricin 环的明显不同的结合方向，对 EF-G 在易位过程中的作用机制提出了有趣的启示。
