Member of the two-component regulatory system BaeS/BaeR which responds to envelope stress (PubMed:12354228, PubMed:21317898). Activates expression of periplasmic chaperone spy in response to spheroplast formation, indole and P pili protein PapG overexpression (PubMed:12354228). Activates BaeR by phosphorylation which then activates the mdtABCD (PubMed:12107134) and probably the CRISPR-Cas casABCDE-ygbT-ygbF operons (PubMed:21255106). ATP + protein L-histidine = ADP + protein N-phospho-L-histidine. Autophosphorylated. Loss of induction of the CRISPR-Cas casABCDE-ygbT-ygbF operon (PubMed:21255106).