Ferric Reductase Activity Of The ArsH Protein From Acidithiobacillus Ferrooxidans

Arsenic resistance genes are widespread in bacteria and eukaryotes, four arsenic-resistance genes (arsB, arsC, arsH, arsR) have been discovered in Acidithiobacillus ferrooxidans. Their gene sequences have been identified and three different arsenic-resistance mechanisms have been elucidated, however, the bio-function of the arsH in At.ferrooxidans remains unclear.In order to evaluate the function of the arsH gene, we cloned and expressed the gene from A.ferrooxidans in E.coli, and purified the ArsH protein by one-step affinity chromatography, with a molecular mass of 28 kDa, contained FMN domain.The ArsH protein was annotated as a NADPH-dependent FMN reductase.Here we reported for the first time that the ArsH protein showed high ferric reductase activity and constructed the mutant expression plasmid(E104A, E104D, E104Q) of the protein using site-directed mutagenesis. The UV-Vis scanning and activity test results confirmed that Glu104 was an essential residue for maintaining the stability of the FMN cofactor. The ArsH protein may perform an important role for cytosolic ferric iron assimilation in vivo.