regulates protein(s) and two-component regulatory system modulating antibiotic efflux arnA ugd PmrF basRS BasRS is a two-component regulatory system. BasR is phosphorylated by BasS at high[Fe3+] levels. The BasRS system regulates the expression of pmrE, pmrF and pmrC, leading to antibiotic resistance. ARO:3003579 antibiotic_resistance pmrAB