HUMAN CYTOPLASMIC ISOLEUCYL-TRANSFER-RNA SYNTHETASE - SELECTIVE DIVERGENCE OF THE ANTICODON-BINDING DOMAIN AND ACQUISITION OF A NEW STRUCTURAL UNIT
HUMAN CYTOPLASMIC ISOLEUCYL-TRANSFER-RNA SYNTHETASE - SELECTIVE DIVERGENCE OF THE ANTICODON-BINDING DOMAIN AND ACQUISITION OF A NEW STRUCTURAL UNIT
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DOI：
10.1073/pnas.91.16.7435
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发表时间：
1994-08-02
影响因子：
11.1
通讯作者：
NODA, T
中科院分区：
文献类型：
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作者：
SHIBA, K;SUZUKI, N;NODA, T
我们在这里表明，I类人细胞质异亮氨酰-tRNA合成酶是一个非常大的多肽（1266 aa），它不同于其在低等真核生物和原核生物中的同系物，具有第三个结构域的两个重复的近似90-aa序列附加到其C-末端。虽然大肠杆菌的提取物不能用异亮氨酸氨酰化哺乳动物的tRNA，但克隆的人基因在大肠杆菌中的表达。大肠杆菌导致哺乳动物tRNA底物带电。附加的第三个结构域是用于检测这种氨酰化活性的，并且可能是在哺乳动物细胞中组装多合成酶复合物所需要的。对大肠杆菌异亮氨酰-tRNA合成酶共有的其余两个结构域的序列进行比对。从大肠杆菌到人的转化揭示了tRNA受体螺旋相互作用和催化所需的结构域比与反密码子相互作用所需的结构域具有更大的选择压力。这一结果可能对氨基酸的操作RNA代码的历史发展有影响。
We show here that the class I human cytoplasmic isoleucyl-tRNA synthetase is an exceptionally large polypeptide (1266 aa) which, unlike its homologues in lower eukaryotes and prokaryotes, has a third domain of two repeats of an approximate to 90-aa sequence appended to its C-terminal end. While extracts of Escherichia call do not aminoacylate mammalian tRNA with isoleucine, expression of the cloned human gene in E. coli results in charging of the mammalian tRNA substrate. The appended third domain is dispensable for detection of this aminoacylation activity and may be needed for assembly of a multisynthetase complex in mammalian cells. Alignment of the sequences of the remaining two domains shared by isoleucyl-tRNA synthetases from E. coli to human reveals a much greater selective pressure on the domain needed for tRNA acceptor helix interactions and catalysis than on the domain needed for interactions with the anticodon. This result may have implications for the historical development of an operational RNA code for amino acids.