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首页> 外文期刊>Journal of Molecular Biology >Prevention of mis-aminoacylation of a dual-specificity aminoacyl-tRNA synthetase.
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Prevention of mis-aminoacylation of a dual-specificity aminoacyl-tRNA synthetase.

机译：防止双重特异性氨基酰基-tRNA合成酶的错误氨基酰化。

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摘要

Accurate aminoacylation of tRNAs by aminoacyl-tRNA synthetase is essential for the fidelity of protein synthesis. For Methanococcus jannaschii tRNA(Pro), accuracy is difficult because the cognate prolyl-tRNA synthetase also recognizes and aminoacylates tRNA(Cys) with cysteine. We show here that the unmodified transcript of M. jannaschii tRNA(Pro) is indeed mis-acylated with cysteine. However, the origin of mis-charging is not at the anticodon or acceptor stem, the two hotspots for tRNA(Pro) and tRNA(Cys) identity determinants. Instead, replacement of the D loop in the tRNA core with that of tRNA(Cys) suppresses mis-charging with cysteine without compromising the activity of aminoacylation with proline. The reduced level of cysteine activity of the chimera is not due an editing response of the synthetase and is consistent with a relaxed sensitivity of the tRNA to the analog thiaproline in aminoacylation with cysteine. We suggest that mis-acylation is not due to the presence of cysteine determinants, but to a mis-placed 3' end into the cysteine catalytic site that activates and transfers cysteine to the tRNA. Prevention of mis-placement by alteration of the core structure or by nucleotide modifications in the tRNA illustrates a novel strategy of the dual-specificity synthetase.
机译：氨酰基-tRNA合成酶对tRNA进行准确的氨酰化对于蛋白质合成的保真度至关重要。对于詹氏甲烷球菌tRNA（Pro），准确性很困难，因为相关的脯氨酰tRNA合成酶还可以识别半胱氨酸tRNA（Cys）并将其氨酰化。我们在这里显示，M。jannaschii tRNA（Pro）的未修饰转录本确实被半胱氨酸错误酰化。但是，误充电的根源不是反密码子或受体茎，tRNA（Pro）和tRNA（Cys）身份决定因素是两个热点。相反，用tRNA（Cys）替换tRNA核心中的D环可抑制半胱氨酸带错电荷，而不会损害脯氨酸的氨酰化活性。嵌合体半胱氨酸活性水平的降低不是由于合成酶的编辑反应，并且与在半胱氨酸氨基酰化中tRNA对类似的噻脯氨酸的松弛敏感性相一致。我们建议错误的酰化不是由于半胱氨酸决定簇的存在，而是由于错位的3'端进入激活并转移半胱氨酸到tRNA的半胱氨酸催化位点。通过核心结构的改变或tRNA中核苷酸的修饰来防止错位，说明了双特异性合成酶的新策略。

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