Protein Domain : Signal transduction protein PmrD superfamily IPR038679

Type	Homologous_superfamily
Description	PmrA/PmrB and PhoP/PhoQ are a pair of two-component systems (TCSs) that allow the Gram-negative bacteria to survive the cationic antimicrobial peptide polymyxin B. The two TCSs are linked by the polymyxin resistance protein, PmrD [ ]. This entry represents a domain found in PmrD. This domain can also be found in anti-adapter protein IraM, a protein which inhibits rpoS proteolysis by regulating rssB activity, thereby increasing the stability of the sigma stress factor rpoS during magnesium starvation []. The Salmonella PmrA/PmrB two-component system is required for resistance to the cationic peptide antibiotic olymyxin B, resistance to Fe(3+)-mediated killing, growth in soil, virulence in mice, and infection of chicken macrophages. PmrA-activated genes encode periplasmic and integral membrane proteins as well as cytoplasmic products mediating the modification of the lipopolysaccharide, suggesting a role for the PmrA/PmrB system in remodeling of the Gram-negative envelope [ ].The PmrA/PmrB two-component system of Salmonella enterica is activated by Fe(3+), which is sensed by the PmrB protein, and by low Mg(2+), which is sensed by the PhoQ protein. The low Mg(2+) activation requires pmrD, a PhoPPhoQ-activated gene that activates the response regulator PmrA at a posttranscriptional level. However, under conditions that activate the PmrA protein independently of pmrD, such as exposure to Fe3, lower levels of pmrD transcription occur. It has been demonstrated that PmrA binds to the pmrD promoter, suppressing transcription. Negative regulation of the PhoP/PhoQ-activated pmrD gene by the PmrA/ PmrB system closes a regulatory circuit designed to maintain proper cellular levels of activated PmrA protein, and constitutes a singular example of a multicomponent feedback loop [ , ].
Short Name	PmrD_sf