Member of the two-component regulatory system DpiA/DpiB, which is essential for expression of citrate-specific fermentation genes and genes involved in plasmid inheritance. Could be involved in response to both the presence of citrate and external redox conditions. Functions as a sensor kinase that phosphorylates DpiA in the presence of citrate. ATP + protein L-histidine = ADP + protein N-phospho-L-histidine. Autophosphorylation is induced in vitro by dithiothreitol (DTT). The periplasmic domain binds citrate with high affinity. The C-terminal cytoplasmic domain senses reduced conditions using a single Cys in vitro. Autophosphorylated.