• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Journal of Molecular Biology >Crystal structure of the polyextremophilic alpha-amylase AmyB from Halothermothrix orenii: Details of a productive enzyme-substrate complex and an N domain with a role in binding raw starch
【24h】

Crystal structure of the polyextremophilic alpha-amylase AmyB from Halothermothrix orenii: Details of a productive enzyme-substrate complex and an N domain with a role in binding raw starch

机译：Halothermothrix orenii的多嗜性α-淀粉酶AmyB的晶体结构：详细的生产性酶-底物复合物和一个与原始淀粉结合的N结构域

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The gene for a membrane-bound, halophilic, and thermostable alpha-amylase, AmyB, from Halothermothrix orenii was cloned and sequenced. The crystal structure shows that, in addition to the typical domain organization of family 13 glycoside hydrolases, AmyB carries an additional N-terminal domain (N domain) that forms a large groove-the N-C groove some 30 angstrom away from the active site. The structure of AmyB with the inhibitor acarbose at 1.35 angstrom resolution shows that a nonasaccharide has been synthesized through successive transglycosylation reactions of acarbose. Unexpectedly, in a complex of wild-type AmyB with alpha-cyclodextrin and maltoheptaose at 2.2 angstrom resolution, a maltotetraose molecule is bound in subsites -1 to +3, spanning the cleavage point at -1 / + 1, with the -1 glucosyl residue present as a S-2(o) skew boat. This wild-type AmyB complex was obtained in the presence of a large excess of substrate, a condition under which it is possible to capture Michaelis complexes, which may explain the observed binding across -1/+ 1 and ring distortion. We observe three methionine side chains that serve as '' binding platforms '' for glucosyl rings in AmyB, a seemingly rare occurrence in carbohydrate-binding proteins. The structures and results from the biochemical characterization of AmyB and AmyB lacking the N domain show that the N domain increases binding of the enzyme to raw starch. Furthermore, theoretical modeling suggests that the N-C groove can accommodate, spatially and chemically, large substrates such as A-starch. (c) 2008 Elsevier Ltd. All rights reserved.
机译：克隆和测序了来自哈氏嗜热菌的膜结合的，嗜盐的和热稳定的α-淀粉酶AmyB的基因。晶体结构表明，除了家族13糖苷水解酶的典型结构域结构外，AmyB还带有一个额外的N末端结构域（N域），该结构域形成了一个大凹槽-距离活性位点约30埃的N-C凹槽。具有1.35埃分辨率的阿卡波糖抑制剂的AmyB的结构表明，通过连续的阿卡波糖转糖基化反应已合成了九糖。出乎意料的是，在野生型AmyB与α-环糊精和麦芽七糖以2.2埃的分辨率形成的复合物中，麦芽四糖分子结合在子位点-1至+3中，跨越了-1 / + 1处的裂解点，而-1葡萄糖残留物以S-2（o）斜舟的形式存在。该野生型AmyB复合物是在大量过量的底物存在下获得的，在这种条件下，可以捕获Michaelis复合物，这可以解释观察到的跨-1 / + 1结合和环畸变。我们观察到三个蛋氨酸侧链充当AmyB中糖基环的“结合平台”，这在碳水化合物结合蛋白中似乎很少见。 AmyB和缺乏N结构域的AmyB的生化表征的结构和结果表明，N结构域增加了酶与生淀粉的结合。此外，理论模型表明，N-C凹槽可以在空间和化学方面容纳较大的基材，例如A-淀粉。 （c）2008 Elsevier Ltd.保留所有权利。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号