Member of the two-component regulatory system ArlS/ArlR involved in the regulation of adhesion, autolysis, multidrug resistance and virulence. ArlS probably functions as a sensor protein kinase which is autophosphorylated at a histidine residue and transfers its phosphate group to ArlR. ArlS/ArlR affects expression of the multidrug resistance transporter norA and interacts with both Agr (virulence accessory gene regulator) (negatively) and SarA (staphylococcal accessory regulator) (positively) to modulate several virulence factor genes, including ssp (serine protease), spa (surface protein A) and hla (alpha-hemolysin). Could inhibit biofilm development by a mechanism independent of the presence of the poly-N-acetylglucosamine (PNAG). Also, Arl proteins are required for the efficient activity of DNA gyrase inhibitors and high osmolarity on spa expression. ATP + protein L-histidine = ADP + protein N-phospho-L-histidine. Activated by agr, SarA, SarV and MgrA. Autophosphorylated.