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首页> 外文期刊>Biochemistry >Crystal structure analysis of the activation of histidine by Thermus thermophilus histidyl-tRNA synthetase.
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Crystal structure analysis of the activation of histidine by Thermus thermophilus histidyl-tRNA synthetase.

机译：嗜热栖热菌组氨酸-tRNA合成酶激活组氨酸的晶体结构分析。

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摘要

The crystal structure at 2.7 A resolution of histidyl-tRNA synthetase (HisRS) from Thermus thermophilus in complex with its amino acid substrate histidine has been determined. In the crystal asymmetric unit there are two homodimers, each subunit containing 421 amino acid residues. Each monomer of the enzyme consists of three domains: (1) an N-terminal catalytic domain containing a six-stranded antiparallel beta-sheet and the three motifs common to all class II aminoacyl-tRNA synthetases, (2) a 90-residue C-terminal alpha/beta domain which is common to most class IIa synthetases and is probably involved in recognizing the anticodon stem-loop of tRNA(His), and (3) a HisRS-specific alpha-helical domain inserted into the catalytic domain, between motifs II and III. The position of the insertion domain above the catalytic site suggests that it could clamp onto the acceptor stem of the tRNA during aminoacylation. Two HisRS-specific peptides, 259-RGLDYY and 285-GGRYDG, are intimately involved in forming the binding site for the histidine, a molecule of which is found in the active site of each monomer. The structure of HisRS in complex with histidyl adenylate, produced enzymatically in the crystal, has been determined at 3.2 A resolution. This structure shows that the HisRS-specific Arg-259 interacts directly with the alpha-phosphate of the adenylate on the opposite side to the usual conserved motif 2 arginine. Arg-259 thus substitutes for the divalent cation observed in seryl-tRNA synthetase and plays a crucial catalytic role in the mechanism of histidine activation.
机译：已经确定了嗜热栖热菌及其氨基酸底物组氨酸的2.7 A分辨率的组氨酸-tRNA合成酶（HisRS）的晶体结构。在晶体不对称单元中，有两个同二聚体，每个亚基包含421个氨基酸残基。该酶的每个单体均由三个结构域组成：（1）包含六链反平行β-折叠的N末端催化结构域和所有II类氨酰基-tRNA合成酶共有的三个基序，（2）90个残基的C -末端α/β结构域，是大多数IIa类合成酶共有的，可能参与识别tRNA（His）的反密码子茎环，以及（3）插入催化结构域之间的HisRS特异性α-螺旋结构域之间，图案II和III。插入位点在催化位点上方的位置表明，它可以在氨基酰化过程中夹在tRNA的受体茎上。两种HisRS特异性肽259-RGLDYY和285-GGRYDG与形成组氨酸的结合位点密切相关，在每个单体的活性位点均发现了其分子。晶体中酶促产生的与组氨酸腺苷酸复合的HisRS结构已在3.2 A的分辨率下测定。这种结构表明，HisRS特异的Arg-259与通常保守的基序2精氨酸相反的一侧与腺苷酸的α-磷酸直接相互作用。因此，Arg-259替代了在seryl-tRNA合成酶中观察到的二价阳离子，并在组氨酸激活机制中起着至关重要的催化作用。

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