The ArsC protein encoded by the arsenical resistance operon of plasmid R773 catalyzes the reduction of arsenate to arsenite in E. colt. The reductase has been shown to require reduced glutathione (GSH) and glutaredoxin (Grx), a small protein participating in electron transfer. To examine the interaction between ArsC and Grx, the sequence for six histidine codons was added to the 5; start of the arsC. Purified Histagged ArsC was bound to a Ni affinity column. Grx also bound to the column if the histagged ArsC was present. This interaction required the substrate, arsenate, or competitive inhibitors phosphate or sulfate. These results indicate direct interaction of ArsC and Grx.
