“…Assuming that the production of dimethylarsinoyl-hydroxycarboxylic acids reflects a partial activity of SsArsS, the role of cysteine residues in that activity was examined. Thiol chemistry plays an important role in arsenic metabolism 24,25 and transport processes 26 through formation of metalloid-sulfur bonds between arsenic and related proteins. Each of the 11 cysteine residues in SsArsS protein, Cys 41 , Cys 45 , Cys 48 , Cys 65 , Cys 129 , Cys 142 , Cys 264 , Cys 279 , Cys 320 , Cys 323 , and Cys 331 , were individually changed to serine residues.…”