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首页> 外文期刊>Acta crystallographica.Section D. Biological crystallography >A new crystal form of XT6 enables a significant improvement of its diffraction quality and resolution
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A new crystal form of XT6 enables a significant improvement of its diffraction quality and resolution

机译：一个新的水晶XT6使一个重要形式改善其衍射质量和决议

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摘要

Xylanases (1,4-beta-D-xylan xylanhydrolases; EC 3.2.1.8) hydrolyze the 1,4-beta-D-xylopyranosyl linkage of xylans. The detailed structural characterization of these enzymes is of interest for the elucidation of their catalytic mechanism and for their rational modification toward improved stability and specificity. An extracellular xylanase from Geobacillus stearothermophilus T-6 (XT6) has recently been cloned, overexpressed, purified and biochemically characterized. Previous crystallographic efforts resulted in a hexagonal crystal form, which subsequently proved to be of limited use for structural analysis, mainly because of its relatively poor diffraction quality and resolution. A systematic search for more suitable crystals of XT6 recently resulted in a new crystal form of this enzyme with significantly improved diffraction characteristics. The new crystals belong to a C-centred monoclinic crystal system (space group C2), with unit-cell parameters a=121.5, b=61.7, c=89.1 Angstrom, beta=119.7degrees. These crystals diffract X-rays to better than 1.5 Angstrom resolution, showing a very clear diffraction pattern of relatively high quality. The crystals are mechanically strong and exhibit excellent radiation-stability when frozen under cold nitrogen gas. A full diffraction data set to 1.45 Angstrom resolution (94.1% completeness, R-merge=7.0%) has been collected from ash-frozen crystals of the native enzyme at 95 K using synchrotron radiation. Crystals of the E159A/E265 A catalytic double mutant of XT6 were found to be isomorphous to those of native XT6. They were used for a full measurement of 1.8 Angstrom resolution diffraction data at 100 K (90.9% completeness; R-merge=5.0%). These data are currently being used for the high-resolution structure determination of XT6 and its mutant for mechanistic interpretations and rational introduction of thermostability.
机译：木聚糖酶(4-beta-D-xylan xylanhydrolases;3.2.1.8)水解1,4-beta-D-xylopyranosyl木聚糖的链接。描述这些酶是感兴趣的说明他们的催化机理和合理的修改的方向提高稳定性和特异性。从Geobacillus胞外木聚糖酶stearothermophilus T-6 (XT6)最近克隆、过表达、纯化和生化反应为特征。导致一个六角晶体形式,后来被证明是有限的使用结构分析,主要因为它的相对贫穷的衍射质量和决议。晶体XT6最近导致了一个新的晶体形式的这种酶显著改进的衍射特性。水晶属于C-centred单斜晶体系统(空间群C2),晶胞参数= 121.5,= 61.7 b, c = 89.1埃,β= 119.7度。比1.5埃分辨率,显示非常清晰的衍射模式相对较高质量。表现出优秀的radiation-stability当冻结在冷氮气。设置为1.45埃分辨率(94.1%完整性、R-merge = 7.0%)已经被收集从ash-frozen原生酶的晶体使用同步辐射95 K。E159A / XT6 E265催化双突变体发现是同形的本机XT6。他们被用于一个完整的测量为1.8在100 K埃分辨率衍射数据(90.9%的完整性;目前正在使用的高分辨率结构测定XT6及其突变体机械的解释和合理引入热稳定性。

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