Member of the two-component regulatory system EnvZ/OmpR involved in regulating expression of the outer membrane porins OmpC and OmpF as well as other genes. Unlike E.coli or S.typhimurium both porins are expressed constitutively. Involved in regulation of the biosynthesis of Vi polysaccharide, a capsular antigen thought to be involved in the virulence of S.typhi. Vi antigen is synthesized at low NaCl concentrations (under 0.4 M) (PubMed:8063417). EnvZ functions as a membrane-associated protein kinase that phosphorylates OmpR in response to environmental signals (By similarity). ATP + protein L-histidine = ADP + protein N-phospho-L-histidine. Homodimer. Has several major domains; the N-terminal cytoplasmic domain is followed by 2 transmembrane helices that anchor the protein in the membrane; the periplasmic domain between the helices interacts with MrzA. The cytoplasmic C-terminal domain has a HAMP domain joined by a flexible linker to a histidine kinase domain. The HAMP domain by itself is intrinsically disordered. The cytoplasmic dimerization domain (CDD) forms an osmosensitive core and includes the autophosphorylated histidine residue. Autophosphorylated.