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首页> 外文期刊>Journal of Molecular Biology >THE CRYSTAL STRUCTURE OF AN FE-SUPEROXIDE DISMUTASE FROM THE HYPERTHERMOPHILE AQUIFEX PYROPHILUS AT 1.9 ANGSTROM RESOLUTION - STRUCTURAL BASIS FOR THERMOSTABILITY
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THE CRYSTAL STRUCTURE OF AN FE-SUPEROXIDE DISMUTASE FROM THE HYPERTHERMOPHILE AQUIFEX PYROPHILUS AT 1.9 ANGSTROM RESOLUTION - STRUCTURAL BASIS FOR THERMOSTABILITY

机译：1.9角分辨率下超嗜热扁桃体超氧化铁歧化的晶体结构-可热性的结构基础

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摘要

Superoxide dismutase (SOD) from Aquifex pyrophilus, a hyperthermophilic bacterium, is an extremely heat-stable enzyme that maintains about 70% of its activity after heat treatment for 60 minutes at 100 degrees C. To understand the molecular basis of thermostability of this enzyme, we have determined the crystal structure of A. pyrophilus superoxide dismutase (Ap SOD), an Fe containing homotetrameric enzyme, at 1.9 Angstrom resolution, and compared it with SOD structures from a mesophile and a thermophile, and other enzyme structures from other hyperthermophiles. The structure has been refined to a crystallographic X-factor (I > 2 sigma) of 17.0% and R-free (I > 2 sigma) of 19.9%. While the overall structure of the Ap SOD monomer is similar to the other SODs, significant conformational differences are observed in a highly variable loop region and the C-terminal helix. The conformational differences in these regions alter the subunit arrangement of this enzyme and generate a very compact tetramer. Structural comparisons of three SODs have revealed that Ap SOD has some stabilizing features at both the tertiary and the quaternary structural level: The Ap SOD monomer contains a large number of ion-pairs and the Ap SOD tetramer has a dramatically increased buried surface area per monomer. Comparisons of the Ap SOD structure with that of other known enzymes from hyperthermophiles reveal that the increased number of intrasubunit ion-pairs is a common feature. (C) 1997 Academic Press Limited. [References: 44]
机译：来自嗜热嗜热菌Aquifex pyrophilus的超氧化物歧化酶（SOD）是一种非常热稳定的酶，在100摄氏度的温度下热处理60分钟后，其活性保持约70％。要了解该酶的热稳定性的分子基础，我们已经确定了嗜铁曲霉超氧化物歧化酶（Ap SOD）（一种含铁的四聚酶）在1.9埃分辨率下的晶体结构，并将其与中嗜和嗜热菌的SOD结构以及其他超嗜热菌的其他酶结构进行了比较。该结构已精炼到17.0％的晶体X因子（I> 2 sigma）和19.9％的无R（I> 2 sigma）。尽管Ap SOD单体的总体结构与其他SOD相似，但在高度可变的环区域和C末端螺旋结构中观察到明显的构象差异。这些区域的构象差异改变了该酶的亚基排列，并产生了非常紧凑的四聚体。三种SOD的结构比较表明，Ap SOD在三级和四级结构水平上均具有一些稳定特征：Ap SOD单体包含大量离子对，Ap SOD四聚体每个单体的隐埋表面积显着增加。 Ap SOD结构与超嗜热菌中其他已知酶的结构比较表明，亚单位内离子对数量增加是一个共同特征。 （C）1997 Academic Press Limited。 [参考：44]

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