THE ACTIVE-SITE OF YEAST ASPARTYL-TRANSFER-RNA SYNTHETASE - STRUCTURAL AND FUNCTIONAL-ASPECTS OF THE AMINOACYLATION REACTION
THE ACTIVE-SITE OF YEAST ASPARTYL-TRANSFER-RNA SYNTHETASE - STRUCTURAL AND FUNCTIONAL-ASPECTS OF THE AMINOACYLATION REACTION
复制标题
DOI：
10.1002/j.1460-2075.1994.tb06265.x
复制
发表时间：
1994-01-15
期刊：
影响因子：
11.4
通讯作者：
MORAS, D
中科院分区：
文献类型：
--
作者：
CAVARELLI, J;ERIANI, G;MORAS, D
酵母天冬氨酰-tRNA合成酶(ASPR)及其底物形成的各种复合体的晶体结构提供了对应于氨基酰化反应不同步骤的活性部位的快照。将tRNA-ASprs的天然晶体浸泡在含有另外两种底物的溶液中，即ATP(或其类似物AMPPcP)和天冬氨酸。当所有底物都存在于晶体中时，这会导致天冬氨酸腺苷和/或天冬氨酰-tRNA的形成。提出了一种II类特异的氨酰化反应途径，解释了这两类之间已知的功能差异，同时保留了一个共同的框架。具有II类AAR特征的扩展签名序列(基序2和3)构成基本功能单元。ATP分子采用弯曲构象，由Motif 3的不变Arg531和与焦磷酸基团配位的镁离子和两个类别不变的酸性残基稳定。天冬氨酸底物由一个II类不变的酸性残基Asp342定位，它与氨基相互作用，并由天冬氨酸合成酶家族保守的氨基酸定位。与底物接触的氨基酸已经通过定点突变进行了功能研究。
The crystal structures of the various complexes formed by yeast aspartyl-tRNA synthetase (AspRS) and its substrates provide snapshots of the active site corresponding to different steps of the aminoacylation reaction. Native crystals of the binary complex tRNA-AspRS were soaked in solutions containing the two other substrates, ATP (or its analog AMPPcP) and aspartic acid. When all substrates are present in the crystal, this leads to the formation of the aspartyl-adenylate and/or the aspartyl-tRNA. A class II-specific pathway for the aminoacylation reaction is proposed which explains the known functional differences between the two classes while preserving a common framework. Extended signature sequences characteristic of class II aaRS (motifs 2 and 3) constitute the basic functional unit. The ATP molecule adopts a bent conformation, stabilized by the invariant Arg531 of motif 3 and a magnesium ion coordinated to the pyrophosphate group and to two class-invariant acidic residues. The aspartic acid substrate is positioned by a class II invariant acidic residue, Asp342, interacting with the amino group and by amino acids conserved in the aspartyl synthetase family. The amino acids in contact with the substrates have been probed by site-directed mutagenesis for their functional implication.