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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >A domain for editing by an archaebacterial tRNA synthetase
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A domain for editing by an archaebacterial tRNA synthetase

机译：由古细菌tRNA合成酶编辑的结构域

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摘要

The rules of the genetic code are established by aminoacylations of transfer RNAs by aminoacyl tRNA synthetases. New codon assignments, and the introduction of new kinds of amino acids, are blocked by vigorous tRNA-dependent editing reactions occurring at hydrolytic sites embedded within specialized domains in the synthetases. For some synthetases, these domains were present at the time of the last common ancestor and were fixed in evolution through all three of the kingdoms of life. Significantly, a well characterized domain for editing found in bacterial and eukaryotic threonyl- and all alanyl-tRNA synthetases is missing from archaebacterial threonine enzymes. Here we show that the archaebacterial Methanosarcina mazei ThrRS efficiently misactivates serine, but does not fuse serine to tRNA. Consistent with this observation, the enzyme cleared serine that was linked to threonine-specific tRNAs. M. mazei and most other archaebacterial ThrRSs have a domain, N2(A), fused to the N terminus and not found in bacterial or eukaryotic orthologs. Mutations at conserved residues in this domain led to an inability to clear threonine-specific tRNA mischarged with serine. Thus, these results demonstrate a domain for editing that is distinct from all others, is restricted to just one branch of the tree of life, and was most likely added to archaebacterial ThrRSs after the eukaryote/archaebacteria split.
机译：通过氨基酰基tRNA合成酶通过转移RNA的氨基酰化来建立遗传密码规则。新的密码子分配和新的氨基酸的引入被强大的tRNA依赖性编辑反应所阻断，该反应发生在合成位点内特定结构域内嵌入的水解位点。对于某些合成而言，这些域存在于最后一个共同祖先的时代，并且在生命的所有三个王国中被固定化。重要的是，古细菌苏氨酸酶缺少在细菌和真核苏氨酸-和所有丙氨酰-tRNA合成酶中发现的特征良好的编辑域。在这里，我们显示古细菌甲烷八叠球菌ThrRS有效地激活丝氨酸，但不会将丝氨酸融合到tRNA。与该观察结果一致，该酶清除了与苏氨酸特异性tRNA相关的丝氨酸。马氏甲烷八叠球菌和大多数其他古细菌ThrRSs具有一个域N2（A），与N末端融合，在细菌或真核直系同源物中未发现。该结构域中保守残基的突变导致无法清除丝氨酸带错的苏氨酸特异性tRNA。因此，这些结果证明了一个与所有其他域截然不同的编辑域，仅限于生命树的一个分支，并且最有可能在真核生物/古细菌分裂后添加到古细菌ThrRS中。

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