Member of the two-component regulatory system DctB/DctD, which regulates C4-dicarboxylate transport via regulation of expression of the dctPQM operon and dctA (PubMed:21725012). DctB functions as a membrane-associated protein kinase that phosphorylates DctD in response to environmental signals (By similarity). ATP + protein L-histidine = ADP + protein N-phospho-L-histidine. Autophosphorylated.