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首页> 外文期刊>Acta crystallographica.Section D. Biological crystallography >Structure of XynB, a highly thermostable β-1,4-xylanase from Dictyoglomus thermophilum Rt46B.1, at 1.8 A resolution
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Structure of XynB, a highly thermostable β-1,4-xylanase from Dictyoglomus thermophilum Rt46B.1, at 1.8 A resolution

机译：XynB结构,高度耐热性的β1,4-xylanase Dictyoglomus thermophilumRt46B。

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摘要

Microorganisms employ a large array of enzymes to break down the cellulose and hemicelluloses of plant biomass. These enzymes, especially those with high thermal stability, have many uses in biotechnology. We have solved the crystal structure of a β-1,4-xylanase, XynB, from the extremely thermophilic bacterium Dictyoglomus thermophilum, isolate Rt46B.1. The protein crystallized from 1.6 M ammonium sulfate, 0.2 M HEPES pH 7.2 and 10% glycerol, with unit-cell parameters a = b = 91.3, c = 44.9 A and space group P4_3. The structure was solved at high resolution (1.8 A) by X-ray crystallography, using the method of isomorphous replacement with a single mercury derivative, and refined to a final R factor of 18.3% (R_(free) = 22.1%). XynB has the single-domain fold typical of family 11 xylanases, comprising a jelly roll of two highly twisted β-sheets that create a deep substrate-binding cleft. The two catalytic residues, Glu90 and Glu180, occupy this cleft. Compared with other family 11 xylanases, XynB has a greater proportion of polar surface and has a slightly extended C-terminus that, combined with the extension of β-strand A5, gives additional hydrogen bonding and hydrophobic packing. These factors may account for the enhanced thermal stability of the enzyme.
机译：微生物利用酶的大阵纤维素和半纤维素的分解植物生物量。高的热稳定性,有许多用途生物技术。结构的β1 4-xylanase XynB,从极端嗜热细菌Dictyoglomusthermophilum Rt46B.1隔离。硫酸铵结晶从1.6米,0.2米消息灵通的pH值7.2和10%的甘油,晶胞参数a = b = 91.3, c = 44.9和空间P4_3组。由x射线晶体学,决议(1.8)使用同形替换的方法一个水银导数,精制最后R因子为18.3% (R_(免费)= 22.1%)。单极折叠的典型家庭11吗木聚糖酶,包括两个高度果冻卷扭曲的β表,创建一个深substrate-binding间隙。残留物,Glu90 Glu180,占领这个间隙。与其他家庭11木聚糖酶相比,XynB更大比例的极性表面,稍微延长糖基结合扩展的β链A5,给予额外的氢键和疏水包装。因素可能占增强的热酶的稳定性。

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