Member of the two-component regulatory system DegS/DegU, which plays an important role in the transition growth phase. Acts as both a protein kinase that undergoes autophosphorylation and subsequently transfers the phosphate to DegU, and a protein phosphatase that dephosphorylates phospho-DegU (By similarity). ATP + protein L-histidine = ADP + protein N-phospho-L-histidine. Autophosphorylated.