Functions as a polar differentiation marker. Essential protein that, by localizing in the old pole of dividing cells, controls cell division and maturation, probably through control of DivK phosphorylation status and cellular distribution, which in turn regulates CtrA, a transcriptional regulator of the minB operon. The asymmetrical localization of this protein is probably required for cells to enter a new division cycle (By similarity). ATP + protein L-histidine = ADP + protein N-phospho-L-histidine. Interacts with DivK. Localizes at the old pole of dividing cells. Colocalizes with DivK (By similarity).