Crystal structure of glutamyl-queuosine tRNAAsp synthetase complexed with L-glutamate:: Structural elements mediating tRNA-independent activation of glutamate and glutamylation of tRNAAsp anticodon
Crystal structure of glutamyl-queuosine tRNAAsp synthetase complexed with L-glutamate:: Structural elements mediating tRNA-independent activation of glutamate and glutamylation of tRNAAsp anticodon
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DOI：
10.1016/j.jmb.2008.06.053
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发表时间：
2008-09-19
影响因子：
5.6
通讯作者：
Kern, Daniel
中科院分区：
文献类型：
--
作者：
Blaise, Mickael;Olieric, Vincent;Kern, Daniel
大肠杆菌谷氨酰-核糖核酸合成酶(Glu-Q-RS)是谷氨酰-tRNA合成酶(GluRS)催化核心的类似物，它催化tRNA(Asp)摆动位置上的队列糖谷氨化。尽管Glu-Q-RS和GluRS在结构上有重要的相似之处，但它们的功能性质却截然不同。这两种酶唯一的共同特征是激活Glu形成Glu-AMP，这是转移RNA(TRNA)氨基酰化的中间产物。然而，这两种酶的不同之处在于选择同源氨基酸的机制及其激活机制。而GluRS只在同源tRNA(Glu)存在的情况下选择L-Glu并激活它，而Glu-Q-RS在没有tRNA的情况下形成Glu-AMP。此外，当GluRS将激活的Glu转移到同源tRNA的3‘接受端(Glu)时，Glu-Q-RS将激活的Glu转移到位于非同源tRNA(Asp)反密码子环中的Q34。为了深入了解导致不同氨基酸活化机制的结构元素，我们求解了Glu-Q-RS与Glu的络合物的三维结构，并将其与GluRS.Glu络合物的结构进行了比较。比较了Glu-Q-RS和GluRS的催化位置，结合氨基酸结合实验表明，有限数量的残基决定了两种酶识别和激活氨基酸的不同催化性能。此外，为了探索这两种酶不同氨酰化特性的结构基础，并理解为什么Glu-Q-RS只对34位含有queuosine的tRNA中的tRNA(Asp)进行谷氨酰化，我们进行了tRNA突变分析，以寻找决定Glu-Q-RS识别的tRNA(Asp)元件。对tRNA(Asp)和tRNA(Asn)的分析表明，38位C的存在对Q34的谷氨酰化至关重要。这些结果在tRNA谷氨酰化系统的进化和适应的背景下进行了讨论。(C)2008爱思唯尔有限公司。保留所有权利。
Glutamyl-queuosine tRNA(Asp) synthetase (Glu-Q-RS) from Escherichia coli is a paralog of the catalytic core of glutamyl-tRNA synthetase (GluRS) that catalyzes glutamylation of queuosine in the wobble position of tRNA(Asp). Despite important structural similarities, Glu-Q-RS and GluRS diverge strongly by their functional properties. The only feature common to both enzymes consists in the activation of Glu to form Glu-AMP, the intermediate of transfer RNA (tRNA) aminoacylation. However, both enzymes differ by the mechanism of selection of the cognate amino acid and by the mechanism of its activation. Whereas GluRS selects L-Glu and activates it only in the presence of the cognate tRNA(Glu), Glu-Q-RS forms Glu-AMP in the absence of tRNA. Moreover, while GluRS transfers the activated Glu to the 3' accepting end of the cognate tRNA(Glu), Glu-Q-RS transfers the activated Glu to Q34 located in the anticodon loop of the noncognate tRNA(Asp). In order to gain insight into the structural elements leading to distinct mechanisms of amino acid activation, we solved the three-dimensional structure of Glu-Q-RS complexed to Glu and compared it to the structure of the GluRS.Glu complex. Comparison of the catalytic site of Glu-Q-RS with that of GluRS, combined with binding experiments of amino acids, shows that a restricted number of residues determine distinct catalytic properties of amino acid recognition and activation by the two enzymes. Furthermore, to explore the structural basis of the distinct aminoacylation properties of the two enzymes and to understand why Glu-Q-RS glutamylates only tRNA(Asp) among the tRNAs possessing queuosine in position 34, we performed a tRNA mutational analysis to search for the elements of tRNA(Asp) that determine recognition by Glu-Q-RS. The analyses made on tRNA(Asp) and tRNA(Asn) show that the presence of a C in position 38 is crucial for glutamylation of Q34. The results are discussed in the context of the evolution and adaptation of the tRNA glutamylation system. (c) 2008 Elsevier Ltd. All rights reserved.