Member of the two-component regulatory system EnvZ/OmpR involved in the regulation of osmoregulation (genes ompF and ompC). EnvZ functions as a membrane-associated protein kinase that phosphorylates OmpR in response to environmental signals (By similarity). Unlike E.coli, OmpC is expressed at both low and high osmolarity, while OmpF is expressed at low osmolarity. This two-component system plays a role in virulence (PubMed:2121709, PubMed:8359885). Virulence genes of the vir locus are up-regulated within 30 minutes upon growth in high osmolarity medium (PubMed:2121709). 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. Single gene deletion invades HeLa cells poorly, has a reduced ability to multiply in host cells and does not cause keratoconjunctivitis in guinea pigs. A double ompR-envZ deletion invades HeLa cells less well than the single mutant, has a limited ability to multiply in host cells and does not cause keratoconjunctivitis in guinea pigs (PubMed:2121709). A double ompR-envZ deletion has a lowered rate of infection of HeLa cells. Bacteria are seriously impaired in their ability to spread between host cells. The double deletion strain expresses very low amounts of OmpC and no OmpF (PubMed:8359885).