Member of the two-component regulatory system CarS/CarR that regulates the expression of multiple genes involved in calcium signaling and homeostasis including CarO and CarP (PubMed:26755627). May function as a membrane-associated protein kinase that phosphorylates CarR in response to environmental signals leading to activation of specific gene promoters (Probable). ATP + protein L-histidine = ADP + protein N-phospho-L-histidine.