Member of the two-component regulatory system UvrY/BarA involved in the regulation of carbon metabolism via the CsrA/CsrB regulatory system (PubMed:12193630, PubMed:12533459). Phosphorylates UvrY, probably via a four-step phosphorelay (PubMed:11022030). ATP + protein L-histidine = ADP + protein N-phospho-L-histidine. Autophosphorylated (PubMed:1574005, PubMed:11022030). Activation requires a sequential transfer of a phosphate group from a His in the primary transmitter domain, to an Asp in the receiver domain and to a His in the secondary transmitter domain (Probable). Inactivation of the gene leads to hydrogen peroxide hypersensitivity.