title: Formation of the stoichiometric complex of EnvZ, a histidine kinase, with its response regulator, OmpR.
abstract: EnvZ, a histidine kinase, and its cognate response regulator OmpR of Escherichia coli are responsible for adaptation to external osmotic changes by regulating the levels of the outer membrane porin proteins, OmpF and OmpC. The osmosensor, EnvZ, has dual enzymatic functions with OmpR kinase and OmpR-P phosphatase. Here, we demonstrate that the cytoplasmic kinase domain of EnvZ (EnvZc) and OmpR are able to form a 1:1 complex detected by native PAGE. This indicates that two OmpR molecules can bind to one EnvZc dimer. As this 1:1 EnvZc/OmpR complex is formed even in the presence of a large excess of EnvZc, OmpR binding to EnvZc is co-operative. The complex formation is also observed between EnvZc and phosphorylated OmpR for the phosphatase reaction. OmpR-P bound to EnvZc was readily released upon the addition of OmpR, indicating that OmpR and OmpR-P can compete for the binding to EnvZ. On the basis of these results, a model is discussed to explain how cellular OmpR-P concentrations are regulated in response to medium osmolarity.
authors.affiliation: Department of Biochemistry, Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, NJ 08854, USA.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yoshida
authors.forename: Ling
authors.initials: L
authors.lastname: Qin
authors.forename: Masayori
authors.initials: M
authors.lastname: Inouye
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins; D002413:Cations, Divalent; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D000071677:Histidine Kinase; D009097:Multienzyme Complexes / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D009994:Osmolar Concentration; D018272:Porins / Q000235:genetics / Q000378:metabolism; D011494:Protein Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D015534:Trans-Activators / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002413:Cations, Divalent; D029968:Escherichia coli Proteins; D009097:Multienzyme Complexes; C113724:OmpC protein; C109237:OmpF protein; D018272:Porins; D015534:Trans-Activators; C112177:osmolarity response regulator proteins; D000255:Adenosine Triphosphate; D011494:Protein Kinases; D000071677:Histidine Kinase; C057843:envZ protein, E coli