Both copies function as additional regulators for the tsa locus, specifically for tsaT. Induced by p-toluenesulfonate (TSA), p-toluenecarboxylate (TCA) and p-sulfobenzoate (PSB). When both copies are inactivated, the mutants are unable to grow with TSA, but show normal growth with TCA. Growth with PSB is slightly faster than growth of the wild-type strain.