Regulated interactions between partner and non-partner sensors and response regulators that control glycopeptide resistance gene expression in enterococci

Transcription of the vanA and vanB glycopeptide resistance gene clusters is regulated by the VanRS and VanR(B)S(B) two-component regulatory systems, respectively. Histidine to glutamine substitutions were introduced at positions 164 of VanS and 233 of VanS(B) to prevent autophosphorylation of the sensor kinases and transfer of the phosphate groups to the VanR and VanR(B) response regulators. VanSH(164)Q and VanS(B)H(233)Q abolished activation of VanR and VanR(B) by host kinases. The phosphatase activity of VanS(B)H(233)Q was negatively modulated by vancomycin whereas VanSH(164)Q prevented transcription of the resistance genes under all growth conditions. Cross-talk was detected between VanR(B) and VanS in a vanS(B) null mutant. VanR is required for activation of promoters P-R and P-H allowing transcription of the regulatory (vanRS) and resistance (vanHAXYZ) genes, respectively. Under non-inducing conditions, activation of VanR by cross-talk was blocked by the presence of a multicopy plasmid carrying P-H. Presence of the high-affinity VanR-binding sites of the regulatory region of P-H on the multicopy vector probably sequestered VanR, thereby preventing autoactivation of the P-R promoter. Under such circumstances, stimulation of the host kinase by glycopeptides or moenomycin was required for expression of the resistance genes.