X-ray structure of a membrane-bound β-glycosidase from the hyperthermophilic Archaeon Pyrococcus horikoshii
X-ray structure of a membrane-bound β-glycosidase from the hyperthermophilic Archaeon Pyrococcus horikoshii
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DOI：
10.1002/prot.20203
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发表时间：
2004-11-01
影响因子：
2.9
通讯作者：
Harata, K
中科院分区：
文献类型：
--
作者：
Akiba, T;Nishio, M;Harata, K
超嗜热菌Pyrococcus horikoshii的β-糖苷酶是一种膜结合酶，其优选底物为烷基-β-糖苷。本研究通过X射线晶体学和对接模拟研究了该酶的特殊结构特征，这些特征赋予了该酶极端的热稳定性和底物偏好性。酶在中性表面活性剂存在下结晶，用分子置换法解析晶体结构，并在2.5埃下精制。该酶的主链折叠属于家族1糖基水解酶共有的（β α）（8）桶结构。活性位点位于桶β链C末端的中心。活动场所的深口袋接受一个。糖单元，并且从那里径向延伸的疏水通道结合底物的非糖部分。寡糖和烷基糖苷的对接模拟表明，具有A长脂肪链的烷基糖苷更容易被对接。容纳在疏水通道中。这种微溶酶在其表面上具有一簇疏水残基，位于活性位点通道的远端，并被一大片带正电荷的残基包围。我们建议，这个疏水区域可以插入到膜中，而周围的带正电荷的残基与膜的内表面上的磷酸基团进行有利的接触。因此，该酶可以粘附在其糖脂底物附近的膜上。(C)2004 Wiley-Liss，Inc.
The beta-glycosidase of the hyperthermophilic Archaeon Pyrococcus horikoshii is a membrane-bound enzyme with the preferred substrate of alkyl-beta-glycosides. In this study, the unusual structural features that confer the extreme thermostability and substrate preferences of this enzyme Were investigated by X-ray crystallography and docking simulation. The enzyme was crystallized in the presence of a neutral surfactant and the crystal structure Was solved by the molecular replacement method And refined at 2.5 Angstrom. The main-chain fold of he enzyme belongs to the (betaalpha)(8) barrel structure common to the family 1 glycosyl hydrolases. The active site is located at the center of the C-termini of the barrel beta-strands. The deep pocket of the active site accepts one. sugar unit, and a hydrophobic channel extending radially from there binds the nonsugar moiety of the substrate. The docking simulation for oligosaccharides and alkylglucosides indicated that alkylglucosides with A long aliphatic chain are easily. accommodated in the hydrophobic channel. This sparingly soluble enzyme has a cluster of hydrophobic residues on its surface, situated at the distal end of the Active site channel and surrounded by a large patch of positively charged residues. We propose that this hydrophobic region can be inserted into the membrane while the surrounding positively charged residues make favorable contacts with phosphate groups on the inner surface of the membrane. The enzyme could thus adhere to the membrane in the proximity of its glycolipid substrate. (C) 2004 Wiley-Liss, Inc.