Member of the two-component regulatory system LytR/LytS that regulates genes involved in autolysis, programmed cell death, biofilm formation and cell wall metabolism. Participates also in sensing and responding to host defense cationic antimicrobial peptides (HDPs). Functions as a sensor protein kinase which is autophosphorylated at a histidine residue and transfers its phosphate group to the conserved aspartic acid residue in the regulatory domain of LytR. In turn, LytR binds to the upstream promoter regions of target genes including lrgA and lrgB, to positively regulate their expression. Possesses also a phosphatase activity that dephosphorylates and thus inactivates LytR