A two-step chemical mechanism for ribosome-catalysed peptide bond formation.
A two-step chemical mechanism for ribosome-catalysed peptide bond formation.
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DOI：
10.1038/nature10248
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发表时间：
2011-07-17
期刊：
影响因子：
64.8
通讯作者：
Strobel, Scott A.
中科院分区：
文献类型：
--
作者：
Hiller, David A.;Singh, Vipender;Zhong, Minghong;Strobel, Scott A.
蛋白质合成的化学步骤，即肽键的形成，是由核糖体的大亚基催化的。晶体结构表明，形成肽键的活性位点完全由RNA组成。最近的工作集中在RNA活性位点如何能够以适合蛋白质合成的速率催化这种基本的生物反应。基于重要的核糖体功能基团的缺乏，缺乏对pH的依赖性，以及熵对催化的主要贡献，已经提出核糖体的作用仅限于使底物紧密接近。另外，肽基-tRNA的2′-羟基的重要性和接近零的布朗斯台德系数被认为是核糖体协调质子转移网络的证据。在这里，我们报告的过渡态的肽键形成的基础上，在五个位置的反应中心的肽基-tRNA模拟物的动力学同位素效应分析。我们的研究结果表明，与未催化的反应相比，四面体中间体的形成和亲核氮的质子转移都发生在限速步骤中。与先前的提议不同，该反应不是完全一致的，而是四面体中间体的分解发生在单独的快速步骤中。这表明，除了底物定位，核糖体是通过改变限速过渡态的化学催化。
The chemical step of protein synthesis, peptide bond formation, is catalyzed by the large subunit of the ribosome. Crystal structures have demonstrated that the active site for peptide bond formation is composed entirely of RNA. Recent work has focused on how an RNA active site is able to catalyze this fundamental biological reaction at a suitable rate for protein synthesis. Based on the absence of important ribosomal functional groups, lack of a dependence on pH, and the dominant contribution of entropy to catalysis, it has been suggested that the role of the ribosome is limited to bringing the substrates into close proximity. Alternatively, the importance of the 2′-hydroxyl of the peptidyl-tRNA and a Bronsted coefficient near zero were taken as evidence that the ribosome coordinates a proton-transfer network. Here we report the transition state of peptide bond formation based upon kinetic isotope effect analysis at five positions at the reaction center of a peptidyl-tRNA mimic. Our results indicate that in contrast to the uncatalyzed reaction, formation of the tetrahedral intermediate and proton-transfer from the nucleophilic nitrogen both occur in the rate-limiting step. Unlike previous proposals, the reaction is not fully concerted, instead breakdown of the tetrahedral intermediate occurs in a separate fast step. This suggests that in addition to substrate positioning, the ribosome is contributing to chemical catalysis by changing the rate-limiting transition state.
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影响因子：
--
作者：
Kingery, David A.;Pfund, Emmanuel;Strobel, Scott A.
通讯作者：
Strobel, Scott A.
DOI：
10.1073/pnas.0914192107
发表时间：
2010-02-02
影响因子：
11.1
作者：
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通讯作者：
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作者：
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通讯作者：
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