Arthur Michel, Depardieu Florence, Courvalin Patrice
Microbiology (Reading). 1999 Aug;145 ( Pt 8):1849-1858. doi: 10.1099/13500872-145-8-1849.
Transcription of the vanA and vanB glycopeptide resistance gene clusters is regulated by the VanRS and VanRBSB two-component regulatory systems, respectively. Histidine to glutamine substitutions were introduced at positions 164 of VanS and 233 of VanSB to prevent autophosphorylation of the sensor kinases and transfer of the phosphate groups to the VanR and VanRB response regulators. VanSH164Q and VanSBH233Q abolished activation of VanR and VanRB by host kinases. The phosphatase activity of VanSBH233Q was negatively modulated by vancomycin whereas VanSH164Q prevented transcription of the resistance genes under all growth conditions. Cross-talk was detected between VanRB and VanS in a vanSB null mutant. VanR is required for activation of promoters PR and PH 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 PH. Presence of the high-affinity VanR-binding sites of the regulatory region of PH on the multicopy vector probably sequestered VanR, thereby preventing autoactivation of the PR promoter. Under such circumstances, stimulation of the host kinase by glycopeptides or moenomycin was required for expression of the resistance genes.
万古霉素耐药基因簇vanA和vanB的转录分别由VanRS和VanRBSB两组分调节系统调控。在VanS的第164位和VanSB的第233位引入组氨酸到谷氨酰胺的替换，以防止传感激酶的自磷酸化以及磷酸基团向VanR和VanRB反应调节因子的转移。VanSH164Q和VanSBH233Q消除了宿主激酶对VanR和VanRB的激活作用。VanSBH233Q的磷酸酶活性受到万古霉素的负调控，而VanSH164Q在所有生长条件下均阻止耐药基因的转录。在vanSB缺失突变体中检测到VanRB和VanS之间存在串扰。VanR是激活启动子PR和PH所必需的，分别允许调节基因（vanRS）和耐药基因（vanHAXYZ）的转录。在非诱导条件下，携带PH的多拷贝质粒的存在会阻断串扰对VanR的激活。多拷贝载体上PH调控区域的高亲和力VanR结合位点的存在可能会隔离VanR，从而防止PR启动子的自激活。在这种情况下，耐药基因的表达需要糖肽或莫能菌素对宿主激酶的刺激。
