title: Signal transduction in bacteria: CheW forms a reversible complex with the protein kinase CheA.
abstract: An essential step in the signal transduction pathway of Escherichia coli is the control of the protein kinase activity of CheA by the chemotaxis receptor proteins. This control requires the participation of the CheW protein. Although the biochemical nature of the coupling between the receptors and the kinase is unknown, it is likely that CheW interacts with the receptors and with CheA. In this communication, we report direct measurement of a physical interaction between CheW and CheA. We utilized the equilibrium column chromatography method of Hummel and Dreyer to show that CheW and CheA exhibit reversible binding with the stoichiometry of two CheW monomers per CheA dimer. CheW was found to exist as monomers and CheA was found to exist as dimers by equilibrium analytical ultracentrifugation. The dissociation constant for the CheW-CheA interaction (in 160 mM KCl/5 mM MgCl2, pH 7.4 at 4 degrees C) was determined to be in the physiologically relevant range of 17 microM. No evidence for cooperativity in the association of CheW with CheA was found.
authors.affiliation: Institute of Molecular Biology, University of Oregon, Eugene 97403.
authors.forename: J A
authors.initials: JA
authors.lastname: Gegner
authors.forename: F W
authors.initials: FW
authors.lastname: Dahlquist
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D002630:Chemotactic Factors / Q000378:metabolism*; D002850:Chromatography, Gel; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029968:Escherichia coli Proteins; D000071677:Histidine Kinase; D007700:Kinetics; D008565:Membrane Proteins / Q000302:isolation & purification / Q000378:metabolism*; D000072236:Methyl-Accepting Chemotaxis Proteins; D010957:Plasmids; D011485:Protein Binding; D011494:Protein Kinases / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D001426:Bacterial Proteins; C489103:CheW protein, E coli; D002630:Chemotactic Factors; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D000072236:Methyl-Accepting Chemotaxis Proteins; C051236:CheW protein, Bacteria; D011494:Protein Kinases; D000071677:Histidine Kinase; C000607608:cheA protein, E coli