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首页> 外文期刊>Journal of Molecular Biology >Ligand bound structures of a glycosyl hydrolase family 30 glucuronoxylan xylanohydrolase.
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Ligand bound structures of a glycosyl hydrolase family 30 glucuronoxylan xylanohydrolase.

机译：糖基水解酶家族30的葡糖醛酸木聚糖木聚糖水解酶的配体结合结构。

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摘要

Xylanases of glycosyl hydrolase family 30 (GH30) have been shown to cleave beta-1,4 linkages of 4-O-methylglucuronoxylan (MeGX(n)) as directed by the position along the xylan chain of an alpha-1,2-linked 4-O-methylglucuronate (MeGA) moiety. Complete hydrolysis of MeGX(n) by these enzymes results in singly substituted aldouronates having a 4-O-methylglucuronate moiety linked to a xylose penultimate from the reducing terminal xylose and some number of xylose residues toward the nonreducing terminus. This novel mode of action distinguishes GH30 xylanases from the more common xylanase families that cleave MeGX(n) in accessible regions. To help understand this unique biochemical function, we have determined the structure of XynC in its native and ligand-bound forms. XynC structure models derived from diffraction data of XynC crystal soaks with the simple sugar glucuronate (GA) and the tetrameric sugar 4-O-methyl-aldotetrauronate resulted in models containing GA and 4-O-methyl-aldotriuronate, respectively. Each is observed in two locations within XynC surface openings. Ligand coordination occurs within the XynC catalytic substrate binding cleft and on the structurally fused side beta-domain, demonstrating a substrate targeting role for this putative carbohydrate binding module. Structural data reveal that GA acts as a primary functional appendage for recognition and hydrolysis of the MeGX(n) polymer by the protein. This work compares the structure of XynC with a previously reported homologous enzyme, XynA, from Erwinia chrysanthemi and analyzes the ligand binding sites. Our results identify the molecular interactions that define the unique function of XynC and homologous GH30 enzymes.
机译：糖基水解酶家族30（GH30）的木聚糖酶已显示可切割4-O-甲基葡糖醛酸木聚糖（MeGX（n））的β-1,4键，如沿α-1,2-连接的木聚糖链的位置所示4-O-甲基葡萄糖醛酸（MeGA）部分。这些酶对MeGX（n）的完全水解会导致单取代的醛糖醛酸酯具有4-O-甲基葡糖醛酸酯部分，从还原性末端木糖连接到倒数第二个木糖，并且有一些木糖残基朝向非还原性末端。这种新颖的作用方式将GH30木聚糖酶与更常见的木聚糖酶家族区分开来，该家族的木聚糖酶家族在可及区域切割MeGX（n）。为了帮助理解这种独特的生化功能，我们确定了XynC天然和配体结合形式的结构。 XynC结构模型是从XynC晶体用简单的葡萄糖醛糖酸酯（GA）和四聚糖4-O-甲基-醛糖四氢酸酯浸泡得到的衍射数据得出的，分别生成包含GA和4-O-甲基-醛糖三酸酯的模型。在XynC表面开口内的两个位置观察到每个。配体配位发生在XynC催化底物结合裂隙内和结构融合侧β结构域上，表明该假定的碳水化合物结合模块具有底物靶向作用。结构数据表明，GA充当主要功能性附件，可识别和水解MeGX（n）聚合物。这项工作将XynC的结构与先前报道的来自菊花欧文氏菌的同源酶XynA进行了比较，并分析了配体结合位点。我们的结果确定了定义XynC和同源GH30酶独特功能的分子相互作用。

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