When system is activated independently of PmrD , such as by exposure to Fe3 , the PmrA protein binds to the pmrD promoter .
When the Salmonella PmrA PmrB is activated independently of PmrD , such as by exposure to Fe3 , the PmrA protein binds to the pmrD promoter .
the pmrD promoter harbors binding sites for both PmrA proteins