Member of the two-component regulatory system SaeR/SaeS involved in the regulation of staphylococcal virulence factors in a strain-dependent fashion. Probably functions as a membrane-associated protein kinase that upon sensing the appropriate signal, autophosphorylates and in turn activates the cytosolic response regulator SaeR (By similarity). Modulates the expression of several genes. ATP + protein L-histidine = ADP + protein N-phospho-L-histidine. Autophosphorylated.