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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >A freestanding proofreading domain is required for protein synthesis quality control in Archaea.
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A freestanding proofreading domain is required for protein synthesis quality control in Archaea.

机译：一个独立的校对域是古细菌蛋白质合成质量控制所必需的。

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摘要

Threonyl-tRNA synthetase (ThrRS) participates in protein synthesis quality control by selectively editing the misacylated species Ser-tRNA(Thr). In bacteria and eukaryotes the editing function of ThrRS resides in a highly conserved N-terminal domain distant from the active site. Most archaeal ThrRS proteins are devoid of this editing domain, suggesting evolutionary divergence of quality-control mechanisms. Here we show that archaeal editing of Ser-tRNAThr is catalyzed by a domain unrelated to, and absent from, bacterial and eukaryotic ThrRSs. Despite the lack of sequence homology, the archaeal and bacterial editing domains are both reliant on a pair of essential histidine residues suggestive of a common catalytic mechanism. Whereas the archaeal editing module is most commonly part of full-length ThrRS, several crenarchaeal species contain individual genes encoding the catalytic (ThrRS-cat) and editing domains (ThrRS-ed). Sulfolobus solfataricus ThrRS-cat was shown to synthesize both Thr-tRNAThr and Ser-tRNAThr and to lack editing activity against Ser-tRNAThr. In contrast, ThrRS-ed lacks aminoacylation activity but can act as an autonomous protein in trans to hydrolyze specifically Ser-tRNAThr, or it can be fused to ThrRS-cat to provide the same function in cis. Deletion analyses indicate that ThrRS-ed is dispensable for growth of S. solfataricus under standard conditions but is required for normal growth in media with elevated serine levels. The growth phenotype of the ThrRS-ed deletion strain suggests that retention of the discontinuous ThrRS quaternary structure relates to specific physiological requirements still evident in certain Archaea.
机译：苏糖基-tRNA合成酶（ThrRS）通过选择性编辑错误酰化的物种Ser-tRNA（Thr）参与蛋白质合成质量控制。在细菌和真核生物中，ThrRS的编辑功能位于远离活性位点的高度保守的N末端域。大多数古细菌ThrRS蛋白没有此编辑域，表明质量控制机制的进化差异。在这里，我们显示Ser-tRNAThr的古细菌编辑是由与细菌和真核ThrRS不相关且不存在的域催化的。尽管缺乏序列同源性，古细菌和细菌编辑域都依赖于一对必需的组氨酸残基，暗示了共同的催化机制。尽管古细菌编辑模块是全长ThrRS的最常见组成部分，但一些小月牙鱼物种包含编码催化性（ThrRS-cat）和编辑域（ThrRS-ed）的单个基因。研究表明，Sulfolobus solfataricus ThrRS-cat可以合成Thr-tRNAThr和Ser-tRNAThr，并且缺乏针对Ser-tRNAThr的编辑活性。相反，ThrRS-ed缺乏氨基酰化活性，但可以作为自主蛋白反式水解以特异性水解Ser-tRNAThr，或者可以与ThrRS-cat融合以提供顺式相同的功能。缺失分析表明，在标准条件下，ThrRS-ed对于S. solfataricus的生长是必不可少的，但是在丝氨酸水平升高的培养基中正常生长是必需的。 ThrRS-ed缺失菌株的生长表型表明，不连续的ThrRS四级结构的保留与某些古细菌中仍然明显的特定生理要求有关。

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