Insights into the structure, solvation, and mechanism of ArsC arsenate reductase, a novel arsenic detoxification enzyme
Insights into the structure, solvation, and mechanism of ArsC arsenate reductase, a novel arsenic detoxification enzyme
复制标题
DOI：
10.1016/s0969-2126(01)00672-4
复制
发表时间：
2001-11-01
期刊：
影响因子：
5.7
通讯作者：
Edwards, BFP
中科院分区：
文献类型：
--
作者：
Martin, P;DeMel, S;Edwards, BFP
背景资料：在携带质粒R773的大肠杆菌中，对亚砷酸盐、砷酸盐、亚锑酸盐和亚碲酸盐的抗性由编码ATP依赖性阴离子泵的arsRDABC质粒操纵子赋予。的arsC基因，砷酸盐还原酶（ArsC）的产品，需要有效地催化还原的砷酸盐，亚砷酸盐前extrusion.Results：在这里，我们报告的第一个X-射线晶体结构的ArsC在1.65埃和ArsC复杂的砷酸盐和亚砷酸盐在1.26埃的分辨率。整体褶皱是独一无二的。天然结构显示硫酸根和亚硫酸根离子作为砷酸根和亚砷酸根的类似物结合在活性位点中。砷酸盐与Cys-12在ArsC的活性位点中的共价加合物，其在差异图中分析，显示具有2.18埃的硫-砷距离的四面体几何形状。然而，与亚砷酸盐的相应加合物作为迄今未见的硫砷羟基加合物结合。最后，结合的沃茨（385）的数量在这个高度有序的晶体结构的方法在此分辨率的138个有序residues.Conclusions结构预期的数量的两倍：从加合物的ArsC与其底物（砷酸盐）和与其产品（亚砷酸盐）的结构信息与功能信息从突变和生化研究的ArsC提出了一个合理的反应机制。异常明确的水结构表明该晶体系统在晶体内具有精确的长程有序性，并且蛋白质数据库中的结构低估了晶体结构中结合沃茨数量的上限。
Background: In Escherichia coli bearing the plasmid R773, resistance to arsenite, arsenate, antimonite, and tellurite is conferred by the arsRDABC plasmid operon that codes for an ATP-dependent anion pump. The product of the arsC gene, arsenate reductase (ArsC), is required to efficiently catalyze the reduction of arsenate to arsenite prior to extrusion.Results: Here, we report the first X-ray crystal structures of ArsC at 1.65 Angstrom and of ArsC complexed with arsenate and arsenite at 1.26 Angstrom resolution. The overall fold is unique. The native structure shows sulfate and sulfite ions binding in the active site as analogs of arsenate and arsenite. The covalent adduct of arsenate with Cys-12 in the active site of ArsC, which was analyzed in a difference map, shows tetrahedral geometry with a sulfur-arsenic distance of 2.18 Angstrom. However, the corresponding adduct with arsenite binds as a hitherto unseen thiarsahydroxy adduct. Finally, the number of bound waters (385) In this highly ordered crystal structure approaches twice the number expected at this resolution for a structure of 138 ordered residues.Conclusions: Structural information from the adduct of ArsC with its substrate (arsenate) and with its product (arsenite) together with functional information from mutational and biochemical studies on ArsC suggest a plausible mechanism for the reaction. The exceptionally well-defined water structure indicates that this crystal system has precise long-range order within the crystal and that the upper limit for the number of bound waters in crystal structures is underestimated by the structures in the Protein Data Bank.