Quorum sensing and virulence in Staphylococcus aureus

Arg is a two component regulatory system based around an operon with 2 promoters. Constitutively expresses AgrA (Response protein, activates P3 producing RNAIII), B (transmembrane protein, secretes mature AIP), C (AIP receptor, binds AIP then phosphorylates AgrA) and D (Autoinducing peptide (AIP)). At low cell density concentration of AIP is low AgrC inactive so no phosphorylation of AgrA to activate P3 and produce RNAIII.