Crystal Structure of Sulfide:Quinone Oxidoreductase from Acidithiobacillus ferrooxidans: Insights into Sulfidotrophic Respiration and Detoxification
Crystal Structure of Sulfide:Quinone Oxidoreductase from Acidithiobacillus ferrooxidans: Insights into Sulfidotrophic Respiration and Detoxification
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DOI：
10.1016/j.jmb.2010.03.018
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发表时间：
2010-04-30
影响因子：
5.6
通讯作者：
James, Michael N. G.
中科院分区：
文献类型：
--
作者：
Cherney, Maia M.;Zhang, Yanfei;James, Michael N. G.
硫化物：醌氧化还原酶从嗜酸性和化学无机营养细菌Acidithiobacillusferrooxidans在大肠杆菌中表达和结晶，其X-射线分子结构被确定为2.3埃分辨率的天然未结合的蛋白质在空间群P4（2）2（1）2。癸基鲁比醌结合结构和Cys 160 Ala变体结构随后分别被确定为2.3埃和2.05埃分辨率，空间群为P6（2）22。由硫化物：醌氧化还原酶催化的酶促反应包括硫化物H2S、HS-和S2-氧化成可溶性多硫化物链或八硫环形式的元素硫;这些氧化与泛醌或甲基萘醌的还原偶联。该酶包含两个串联Rossmann折叠结构域和一个柔性C-末端结构域，该结构域包含两个被认为提供膜锚定的两亲性螺旋。第二个两亲螺旋解旋并改变其六方晶体形式的取向。蛋白质形成二聚体，可以插入膜中大约20埃的深度。其具有在N-末端结构域中非共价结合的内源性黄素腺嘌呤二核苷酸（FAD）辅因子。几个宽通道将FAD辅因子连接到蛋白质分子的外部;其中一些通道将提供进入膜的通道。泛醌分子结合在这些通道之一中;其苯醌环堆叠在两个保守的苯丙氨酸残基的芳环之间，并且其紧密接近FAD辅因子的异咯嗪部分。两个活性位点的半胱氨酸残基位于FAD辅因子的背面形成一个分支的多硫桥。Cys 356二硫化物作为亲核试剂，在电子转移反应中攻击FAD辅因子的C4 A原子。第三个必需的半胱氨酸Cys 128在这些结构中没有被修饰;它的作用可能局限于多硫产物的释放。(C)2010爱思唯尔有限公司版权所有。
Sulfide:quinone oxidoreductase from the acidophilic and chemolithotrophic bacterium Acidithiobacillus ferrooxidans was expressed in Escherichia coli and crystallized, and its X-ray molecular structure was determined to 2.3 angstrom resolution for native unbound protein in space group P4(2)2(1)2. The decylubiquinone-bound structure and the Cys160Ala variant structure were subsequently determined to 2.3 angstrom and 2.05 angstrom resolutions, respectively, in space group P6(2)22. The enzymatic reaction catalyzed by sulfide:quinone oxidoreductase includes the oxidation of sulfide compounds H2S, HS-, and S2- to soluble polysulfide chains or to elemental sulfur in the form of octasulfur rings; these oxidations are coupled to the reduction of ubiquinone or menaquinone. The enzyme comprises two tandem Rossmann fold domains and a flexible C-terminal domain encompassing two amphipathic helices that are thought to provide for membrane anchoring. The second amphipathic helix unwinds and changes its orientation in the hexagonal crystal form. The protein forms a dimer that could be inserted into the membrane to a depth of approximately 20 angstrom. It has an endogenous flavin adenine dinucleotide (FAD) cofactor that is noncovalently bound in the N-terminal domain. Several wide channels connect the FAD cofactor to the exterior of the protein molecule; some of the channels would provide access to the membrane. The ubiquinone molecule is bound in one of these channels; its benzoquinone ring is stacked between the aromatic rings of two conserved Phe residues, and it closely approaches the isoalloxazine moiety of the FAD cofactor. Two active-site cysteine residues situated on the re side of the FAD cofactor form a branched polysulfide bridge. Cys356 disulfide acts as a nucleophile that attacks the C4A atom of the FAD cofactor in electron transfer reaction. The third essential cysteine Cys128 is not modified in these structures; its role is likely confined to the release of the polysulfur product. (C) 2010 Elsevier Ltd. All rights reserved.