This protein is involved in several diverse cellular processes, such as the functioning of acetohydroxyacid synthetase I, in the biosynthesis of isoleucine and valine, the TraJ protein activation activity for tra gene expression in F plasmid, and the synthesis, translocation, or stability of cell envelope proteins. Activates CpxR by phosphorylation (By similarity). ATP + protein L-histidine = ADP + protein N-phospho-L-histidine.