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首页> 外文期刊>Acta crystallographica. Section D, Biological crystallography. >Superoxide reductase from Giardia intestinalis: structural characterization of the first SOR from a eukaryotic organism shows an iron centre that is highly sensitive to photoreduction
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Superoxide reductase from Giardia intestinalis: structural characterization of the first SOR from a eukaryotic organism shows an iron centre that is highly sensitive to photoreduction

机译：从鞭毛虫intestinalis过氧化物还原酶:结构表征的第一法师真核生物铁中心,展示了一个高度敏感的光致还原作用吗

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摘要

Superoxide reductase (SOR), which is commonly found in prokaryotic organisms, affords protection from oxidative stress by reducing the superoxide anion to hydrogen peroxide. The reaction is catalyzed at the iron centre, which is highly conserved among the prokaryotic SORs structurally characterized to date. Reported here is the first structure of an SOR from a eukaryotic organism, the protozoan parasite Giardia intestinalis (GiSOR), which was solved at 2.0 angstrom resolution. By collecting several diffraction data sets at 100 K from the same flash-cooled protein crystal using synchrotron X-ray radiation, photoreduction of the iron centre was observed. Reduction was monitored using an online UV-visible microspectrophotometer, following the decay of the 647 nm absorption band characteristic of the iron site in the glutamate-bound, oxidized state. Similarly to other 1Fe-SORs structurally characterized to date, the enzyme displays a tetrameric quaternary-structure arrangement. As a distinctive feature, the N-terminal loop of the protein, containing the characteristic EKHxP motif, revealed an unusually high flexibility regardless of the iron redox state. At variance with previous evidence collected by X-ray crystallography and Fourier transform infrared spectroscopy of prokaryotic SORs, iron reduction did not lead to dissociation of glutamate from the catalytic metal or other structural changes; however, the glutamate ligand underwent X-ray-induced chemical changes, revealing high sensitivity of the GiSOR active site to X-ray radiation damage.
机译：过氧化物还原酶(SOR),这是常见的存在于原核生物,提供从减少氧化应激的保护过氧化氢过氧化物阴离子。反应是催化铁中心,原核中高度保守的传感器适用吗结构特征。琼的第一个结构是一个人吗真核生物、原生动物寄生虫贾第虫属intestinalis (GiSOR),解决了2.0埃分辨率。从相同的衍射数据集在100 K使用同步加速器flash-cooled蛋白质晶体x射线辐射,铁的光致还原作用中心观察。使用在线紫外可见显微分光光度计,衰变后647纳米吸收带的特点铁网站glutamate-bound,氧化状态。类似于其他1 fe-sors结构到目前为止,酶显示四聚物的四级结构安排。独特的特性,氨基的循环蛋白质,含有EKHxP特征主题,揭示异常高的灵活性无论铁氧化还原状态。与先前的证据收集的x射线晶体学和傅里叶变换红外原核的光谱传感器适用、铁还原没有导致谷氨酸的离解吗催化金属或其他结构变化;然而,谷氨酸盐配体进行了X-ray-induced化学变化,揭示高x射线敏感性GiSOR活跃的站点辐射损伤。

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