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. SaeR/SaeS activates the expression of exoproteins involved in adhesion and invasion of host cells, including hemolysins (hla, hlb, hlgC), coa, DNase, spa and cell wall-associated proteins (emp, eap, fnbA, fnbB, efb). Represses the expression of type 5 capsular polysaccharide (cap operon). Also modulates the expression of several other genes. ATP + protein L-histidine = ADP + protein N-phospho-L-histidine. Autophosphorylated.