Biochemical, molecular and in silico characterization of arsenate reductase from Bacillus thuringiensis KPWP1 tolerant to salt, arsenic and a wide range of pH

The present study characterized aresenate reductase of Bacillus thuringiensis KPWP1, tolerant to salt, arsenate and a wide range of pH during growth. Interestingly, it was found that arsC, arsB and arsR genes involved in arsenate tolerance are distributed in the genome of strain KPWP1. The inducible arsC gene was cloned, expressed and the purified ArsC protein showed profound enzyme activity with the K-M and K-cat values as 25 mu M and 0.00119 s(-1), respectively. In silico studies revealed that in spite of 19-26% differences in gene sequences, the ArsC proteins of Bacillus thuringiensis, Bacillus subtilis and Bacillus cereus are structurally conserved and ArsC structure of strain KPWP1 is close to nature. Docking and analysis of the binding site showed that arsenate ion interacts with three cysteine residues of ArsC and predicts that the ArsC from B. thuringiensis KPWP1 reduces arsenate by using the triple Cys redox relay mechanism.