Genetic code ambiguity -: Cell viability related to severity of editing defects in mutant tRNA synthetases
Genetic code ambiguity -: Cell viability related to severity of editing defects in mutant tRNA synthetases
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DOI：
10.1074/jbc.m208093200
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发表时间：
2002-11-29
影响因子：
4.8
通讯作者：
Schimmel, P
中科院分区：
文献类型：
--
作者：
Nangle, LA;Lagardt, VD;Schimmel, P
遗传密码的规则是在用特定氨基酸氨酰化 tRNA 的反应中建立的。通过编辑活动可以防止代码中的歧义，通过氨酰 tRNA 合成酶的专门水解反应清除不正确的氨酰化。尽管编辑反应早已为人所知，但它们对细胞活力的重要性仍知之甚少。在这里，我们在体外和体内研究了编辑中心的四种不同突变，这些突变降低了缬氨酰-tRNA 合成酶 (ValRS) 的校对活性。四种突变酶在体外清除错误带电的 tRNA 的能力缺陷的严重程度存在定量差异。引人注目的是，在过量浓度的α-氨基丁酸（ValRS 失活的氨基酸之一）存在下，带有这些突变等位基因的细菌菌株的生长被抑制。生长停滞所需的失活氨基酸浓度与体外观察到的编辑缺陷的程度呈反相关。因此，细胞活力直接取决于这些特定编辑反应对遗传密码模糊性的抑制，并且可以根据这些反应的任何扰动进行微调。
The rules of the genetic code are established in reactions that aminoacylate tRNAs with specific amino acids. Ambiguity in the code is prevented by editing activities whereby incorrect aminoacylations are cleared by specialized hydrolytic reactions of aminoacyl tRNA synthetases. Whereas editing reactions have long been known, their significance for cell viability is still poorly understood. Here we investigated in vitro and in vivo four different mutations in the center for editing that diminish the proofreading activity of valyl-tRNA synthetase (ValRS). The four mutant enzymes were shown to differ quantitatively in the severity of the defect in their ability to clear mischarged tRNA in vitro. Strikingly, in the presence of excess concentrations of a-aminobutyrate, one of the amino acids that is misactivated by ValRS, growth of bacterial strains bearing these mutant alleles is arrested. The concentration of misactivated amino acid required for growth arrest correlates in. versely in a rank order with the degree of the editing defect seen in vitro. Thus, cell viability depends directly on the suppression of genetic code ambiguity by these specific editing reactions and is finely tuned to any perturbation of these reactions.