Under identical experimental conditions as for argO , the regulatory regions of the other ArgP-regulated genes ( asd , dapB , dapD , gdhA , lysA , lysC , and lysP ) were also bound by ArgP , with apparent K d s ranging from 55 nM to 170 nM ; in all these cases ( unlike the situation with argO ) , the addition of Lys was associated with an increase in the apparent K d , indicating that ArgP binding in these instances is Lys-sensitive .