Member of the two-component regulatory system PmrB/PmrA involved in regulation of virulence. Functions probably as a sensor protein kinase which is autophosphorylated at a histidine residue and transfers its phosphate group to PmrA in response to external pH and iron. ATP + protein L-histidine = ADP + protein N-phospho-L-histidine. Autophosphorylated.