Nature:核糖體的校對功能

專題：Nature報導

體外蛋白質合成研究一直不能完全解釋文獻中所報導的活體蛋白質合成所具有的保真度。DNA 和RNA聚合酶複合物（它們將氨醯基- tRNA輸送到核糖體A-點上）具有校對功能，但此前這種活性一直沒有在核糖體本身中發現。

現在，Hani Zaher 和 Rachel Green發現了一個以前沒有定性的、用於保證蛋白質合成的保真度的體系，該體系在肽鍵形成之後發揮作用。如果一個不正確的胺基酸被吸收進了一個正在生長的多肽鏈中，那麼在核糖體的活性點上特異性一般就會丟失，導致錯誤累積，觸發肽合成的過早結束。這種「後肽基轉移編輯」（post-peptidyl transfer editing），在某種程度上可以解釋活體蛋白質合成中所達到的給人印象深刻的保真度。（生物谷Bioon.com）

生物谷推薦原始出處：

Nature 457, 161-166 (8 January 2009) | doi:10.1038/nature07582

Quality control by the ribosome following peptide bond formation

Hani S. Zaher1 & Rachel Green1

1 Howard Hughes Medical Institute, Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA

The overall fidelity of protein synthesis has been thought to rely on the combined accuracy of two basic processes: the aminoacylation of transfer RNAs with their cognate amino acid by the aminoacyl-tRNA synthetases, and the selection of cognate aminoacyl-tRNAs by the ribosome in cooperation with the GTPase elongation factor EF-Tu. These two processes, which together ensure the specific acceptance of a correctly charged cognate tRNA into the aminoacyl (A) site, operate before peptide bond formation. Here we report the identification of an additional mechanism that contributes to high fidelity protein synthesis after peptidyl transfer, using a well-defined in vitro bacterial translation system. In this retrospective quality control step, the incorporation of an amino acid from a non-cognate tRNA into the growing polypeptide chain leads to a general loss of specificity in the A site of the ribosome, and thus to a propagation of errors that results in abortive termination of protein synthesis.