Department of Life Sciences, School of Natural Sciences, Shiv Nadar University, Gautam Buddha Nagar, Uttar Pradesh, India.
Department of Biotechnology and Bioinformatics, Jaypee University of Information Technology, Waknaghat, Himachal Pradesh, 173234, India.
J Mol Model. 2019 Jan 4;25(1):15. doi: 10.1007/s00894-018-3885-3.
Arsenic prevalence in the environment impelled many organisms to develop resistance over the course of evolution. Tolerance to arsenic, either as the pentavalent [As(V)] form or the trivalent form [As(III)], by bacteria has been well studied in prokaryotes, and the mechanism of action is well defined. However, in the rod-shaped arsenic tolerant Deinococcus indicus DR1, the key enzyme, arsenate reductase (ArsC) has not been well studied. ArsC of D. indicus belongs to the Grx-linked prokaryotic arsenate reductase family. While it shares homology with the well-studied ArsC of Escherichia coli having a catalytic cysteine (Cys 12) and arginine triad (Arg 60, 94, and 107), the active site of D.indicus ArsC contains four residues Glu 9, Asp 53, Arg 86, and Glu 100, and with complete absence of structurally equivalent residue for crucial Cys 12. Here, we report that the mechanism of action of ArsC of D. indicus is different as a result of convergent evolution and most likely able to detoxify As(V) using a mix of positively- and negatively-charged residues in its active site, unlike the residues of E. coli. This suggests toward the possibility of an alternative mechanism of As (V) degradation in bacteria.
由于环境中砷的普遍存在，许多生物在进化过程中发展出了抗性。细菌对砷的耐受性，无论是五价[As(V)]形式还是三价形式[As(III)]，在原核生物中已经得到了很好的研究，其作用机制也已明确。然而，在耐砷的杆状细菌 Deinococcus indicus DR1 中，关键酶砷酸盐还原酶（ArsC）尚未得到很好的研究。D. indicus 的 ArsC 属于 Grx 连接的原核砷酸盐还原酶家族。虽然它与研究充分的大肠杆菌 ArsC 具有同源性，大肠杆菌 ArsC 含有一个催化半胱氨酸（Cys 12）和精氨酸三联体（Arg 60、94 和 107），但 D.indicus ArsC 的活性位点含有四个残基Glu 9、Asp 53、Arg 86 和 Glu 100，并且完全缺乏结构等效的关键 Cys 12 残基。在这里，我们报告说，由于趋同进化，D.indicus ArsC 的作用机制不同，其活性位点中可能使用带正电荷和带负电荷的残基的混合物来解毒 As(V)，而不是大肠杆菌的残基。这表明细菌中可能存在一种替代的 As(V)降解机制。
