Amino-Acid-Dependent Shift in tRNA Synthetase Editing Mechanisms

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• 作者：Jaya Sarkar ; Susan A. Martinis
• 刊名：Journal of the American Chemical Society
• 出版年：2011
• 出版时间：November 23, 2011
• 年：2011
• 卷：133
• 期：46
• 页码：18510-18513
• 全文大小：725K
• 年卷期：v.133,no.46(November 23, 2011)
• ISSN：1520-5126

文摘

Many aminoacyl-tRNA synthetases prevent mistranslation by relying upon proofreading activities at multiple stages of the aminoacylation reaction. In leucyl-tRNA synthetase (LeuRS), editing activities that precede or are subsequent to tRNA charging have been identified. Although both are operational, either the pre- or post-transfer editing activity can predominate. Yeast cytoplasmic LeuRS (ycLeuRS) misactivates structurally similar noncognate amino acids including isoleucine and methionine. We show that ycLeuRS has a robust post-transfer editing activity that efficiently clears tRNA^Leu mischarged with isoleucine. In comparison, the enzyme鈥檚 post-transfer hydrolytic activity against tRNA^Leu mischarged with methionine is weak. Rather, methionyl-adenylate is cleared robustly via an enzyme-mediated pre-transfer editing activity. We hypothesize that, similar to E. coli LeuRS, ycLeuRS has coexisting functional pre- and post-transfer editing activities. In the case of ycLeuRS, a shift between the two editing pathways is triggered by the identity of the noncognate amino acid.