Assembly of an MCP receptor, CheW, and kinase CheA complex in the bacterial chemotaxis signal transduction pathway.
We examined the binding interactions of the methylation-dependent chemotaxis receptors Tsr and Tar with the chemotaxis-specific protein kinase CheA and the coupling factor CheW. Receptor directly bound CheW, but receptor-CheA binding was dependent upon the presence of CheW. These observations in combination with our previous identification of a CheW-CheA complex suggest that CheW physically links the kinase to the receptor. The ternary complex of receptor, CheW, and CheA is both kinetically and thermodynamically stable at physiological concentrations. Stability is not significantly altered by changes associated with attractant or repellent binding to the receptor. Such binding greatly modulates the kinase activity of CheA. Our results demonstrate that modulation of the kinase activity does not require association-dissociation of the ternary complex. This suggests that the receptor signal is transduced through conformational changes in the ternary complex rather than through changes in the association of the kinase CheA with receptor and/or CheW.
Gegner
J A
JA
Institute of Molecular Biology, University of Oregon, Eugene 97403.
Graham
D R
DR
Roth
A F
AF
Dahlquist
F W
FW
D001426:Bacterial Proteins / Q000378:metabolism*; D002628:Chemoreceptor Cells; D002630:Chemotactic Factors / Q000378:metabolism*; D002633:Chemotaxis / Q000502:physiology; D029968:Escherichia coli Proteins; D000071677:Histidine Kinase; D007700:Kinetics; D008565:Membrane Proteins / Q000378:metabolism*; D000072236:Methyl-Accepting Chemotaxis Proteins; D011485:Protein Binding; D011956:Receptors, Cell Surface / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology
D001426:Bacterial Proteins; C489103:CheW protein, E coli; D002630:Chemotactic Factors; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D000072236:Methyl-Accepting Chemotaxis Proteins; D011956:Receptors, Cell Surface; C057331:Tar protein, E coli; C057635:Tsr protein, Bacteria; C000607604:tsr protein, E coli; C051236:CheW protein, Bacteria; D000071677:Histidine Kinase; C000607608:cheA protein, E coli