Member of the two-component regulatory system DcuR/DcuS. Involved in the C4-dicarboxylate-stimulated regulation of the genes encoding the anaerobic fumarate respiratory system (frdABCD; nuoAN; dcuB; dcuC; sdhCDAB; etc.). Weakly regulates the aerobic C4-dicarboxylate transporter dctA. Activates DcuR by phosphorylation (By similarity). ATP + protein L-histidine = ADP + protein N-phospho-L-histidine. Homodimer. The periplasmic domain is involved in C4-dicarboxylate binding and sensing. The structural disorder in the cytoplasmic PAS domain has an important role in signal transduction to the kinase domain and may be the decisive structural feature that characterizes the activated kinase (By similarity). Autophosphorylated. The phosphoryl group is rapidly transferred to DcuR (By similarity).