Meskauskas Arturas, Dinman Jonathan D
Department of Cell Biology and Molecular Genetics, Microbiology Building Rm. 2135, University of Maryland, College Park, MD 20742, USA.
Nucleic Acids Res. 2008 Nov;36(19):6175-86. doi: 10.1093/nar/gkn642. Epub 2008 Oct 2.
Although ribosomal RNAs (rRNAs) comprise the bulk of the ribosome and carry out its main functions, ribosomal proteins also appear to play important structural and functional roles. Many ribosomal proteins contain long, nonglobular domains that extend deep into the rRNA cores. In eukaryotes and Archaea, ribosomal protein L3 contains two such extended domains tethered to a common globular hub, thus providing an excellent model to address basic questions relating to ribosomal protein structure/function relationships. Previous work in our laboratory identified the central 'W-finger' extension of yeast L3 in helping to coordinate ribosomal functions. New studies on the 'N-terminal' extension in yeast suggest that it works with the W-finger to coordinate opening and closing of the corridor through which the 3' end of aa-tRNA moves during the process of accommodation. Additionally, the effect of one of the L3 N-terminal extension mutants on the interaction between C75 of the aa-tRNA and G2921 (Escherichia coli G2553) of 25S rRNA provides the first evidence of the effect of a ribosomal protein on aa-tRNA positioning and peptidyltransfer, possibly through the induced fit model. A model is presented describing how all three domains of L3 may function together as a 'rocker switch' to coordinate the stepwise processes of translation elongation.
尽管核糖体RNA（rRNA）构成了核糖体的主体并执行其主要功能，但核糖体蛋白似乎也发挥着重要的结构和功能作用。许多核糖体蛋白含有长的、非球状结构域，这些结构域深入rRNA核心。在真核生物和古细菌中，核糖体蛋白L3包含两个这样的延伸结构域，它们与一个共同的球状中心相连，因此为解决与核糖体蛋白结构/功能关系相关的基本问题提供了一个极好的模型。我们实验室之前的工作确定了酵母L3的中央“W指”延伸在帮助协调核糖体功能方面的作用。对酵母中“N端”延伸的新研究表明，它与W指协同作用，以协调在接纳过程中aa-tRNA的3'端移动所经过的通道的打开和关闭。此外，L3 N端延伸突变体之一对aa-tRNA的C75与25S rRNA的G2921（大肠杆菌G2553）之间相互作用的影响，首次证明了核糖体蛋白可能通过诱导契合模型对aa-tRNA定位和肽基转移的作用。本文提出了一个模型，描述了L3的所有三个结构域如何作为一个“翘板开关”共同发挥作用，以协调翻译延伸的逐步过程。
