Ghosh Semanti, Bagchi Angshuman
Department of Biochemistry & Biophysics, University of Kalyani, Kalyani 741235, Nadia, India.
Department of Biochemistry & Biophysics, University of Kalyani, Kalyani 741235, Nadia, India.
Comput Biol Chem. 2015 Dec;59 Pt A:177-84. doi: 10.1016/j.compbiolchem.2015.07.001. Epub 2015 Oct 22.
Sulfur metabolism is one of the oldest known redox geochemical cycles in our atmosphere. These redox processes utilize different sulfur anions and the reactions are performed by the gene products of dsr operon from phylogenetically diverse sets of microorganisms. The operon is involved in the maintenance of environmental sulfur balance. Interestingly, the dsr operon is found to be present in both sulfur anion oxidizing and reducing microorganisms and in both types of organisms DsrAB protein complex plays a vital role. Though there are various reports regarding the genetics of dsr operon there are practically no reports dealing with the structural aspects of sulfur metabolism by dsr operon. In our present study, we tried to compare the mechanisms of sulfur anion oxidation and reduction by Allochromatium vinosum and Desulfovibrio vulgaris respectively through DsrAB protein complex. We analyzed the modes of bindings of sulfur anions to the DsrAB protein complex and observed that for sulfur anion oxidizers, sulfide and thiosulfate are the best substrates whereas for reducers sulfate and sulfite have the best binding abilities. We analyzed the binding interaction pattern of the DsrA and DsrB proteins while forming the DsrAB protein complexes in Desulfovibrio vulgaris and Allochromatium vinosum. To our knowledge this is the first report that analyzes the differences in binding patterns of sulfur substrates with DsrAB protein from these two microorganisms. This study would therefore be essential to predict the biochemical mechanism of sulfur anion oxidation and reduction by these two microorganisms i.e., Desulfovibrio vulgaris (sulfur anion reducer) and Allochromatium vinosum (sulfur anion oxidizer). Our observations also highlight the mechanism of sulfur geochemical cycle which has important implications in future study of sulfur metabolism as it has a huge application in waste remediation and production of industrial bio-products viz. vitamins, bio-polyesters and bio-hydrogen.
硫代谢是大气中已知最古老的氧化还原地球化学循环之一。这些氧化还原过程利用不同的硫阴离子，反应由系统发育上不同的微生物组的dsr操纵子的基因产物进行。该操纵子参与环境硫平衡的维持。有趣的是，发现dsr操纵子存在于硫阴离子氧化和还原微生物中，并且在这两种类型的生物体中，DsrAB蛋白复合物都起着至关重要的作用。尽管有关于dsr操纵子遗传学的各种报道，但实际上没有关于dsr操纵子硫代谢结构方面的报道。在我们目前的研究中，我们试图分别通过DsrAB蛋白复合物比较嗜酒色杆菌和普通脱硫弧菌对硫阴离子氧化和还原的机制。我们分析了硫阴离子与DsrAB蛋白复合物的结合模式，观察到对于硫阴离子氧化菌，硫化物和硫代硫酸盐是最佳底物，而对于还原剂，硫酸盐和亚硫酸盐具有最佳结合能力。我们分析了普通脱硫弧菌和嗜酒色杆菌中形成DsrAB蛋白复合物时DsrA和DsrB蛋白的结合相互作用模式。据我们所知，这是第一份分析这两种微生物的硫底物与DsrAB蛋白结合模式差异的报告。因此，这项研究对于预测这两种微生物即普通脱硫弧菌（硫阴离子还原剂）和嗜酒色杆菌（硫阴离子氧化菌）对硫阴离子氧化和还原的生化机制至关重要。我们的观察结果还突出了硫地球化学循环的机制，这对未来硫代谢的研究具有重要意义，因为它在废物修复和工业生物产品（即维生素、生物聚酯和生物氢）的生产中有巨大应用。
