SOFT METAL THIOL CHEMISTRY IS NOT INVOLVED IN THE TRANSPORT OF ARSENITE BY THE ARS PUMP

The single cysteine in the ArsB protein subunit of the arsenite resist ance pump was changed to serine and alanine residues. Resistance in ce lls expressing the two mutant arsB genes was the same as in the wild t ype, and the serine substitution had no effect on the arsenite transpo rt properties. These results eliminate possible thiol chemistry in tra nslocation. Thus, the pump uses soft metal chemistry for metalloactiva tion and nonmetal chemistry for oxyanion transport.