Among the genes were several previously characterized PmrA-activated genes : pmrH ( STM2297 ) , pmrF , pmrC ( yjdB ) , pmrA ( basR ) , pmrB ( basS ) , yibD and pmrG ( ais ) .
Although a non-cytotoxic form of polymyxin B -- termed polymyxin B nonapeptide ( Vaara and Vaara , 1983 ) -- could partially protect a Salmonella pmrA mutant from Fe ( III ) - mediated killing ( Chamnongpol et al. , 2002 ) inactivation of the PmrA-activated loci responsible for the lipid-A modification with 4-aminoarabinose ( i.e. pbgP ) or phosphoethanolamine ( i.e. pmrC ) did not render the organism susceptible to Fe ( III ) ( Lee et al. , 2004 ) .
By contrast , Zn2 + has been shown to promote transcription of the pmrA and pmrB genes as well as that of several PmrA-activated genes in E. coli ( Lee et al. , 2005 ) .