Competitive and cooperative interactions in receptor signaling complexes.
In bacterial chemotaxis, clustered transmembrane receptors and the adaptor protein CheW regulate the kinase CheA. Receptors outnumber CheA, yet it is poorly understood how interactions among receptors contribute to regulation. To address this problem, receptor clusters were simulated using liposomes decorated with the cytoplasmic domains of receptors, which supported CheA binding and stimulation. Competitive and cooperative interactions were revealed through the use of known receptor signaling mutants, which were used in mixtures with the wild type domain. Competitive effects among the receptor domains sorted cleanly into two categories defined by either stronger or weaker interactions with CheA. Cooperative effects were also evident in CheA binding and activity. In the transition from the stimulating to the inhibiting states, both the cooperativity of the transition and the persistence of stimulation by the wild type domain increased with receptor modification, as in the intact receptor. We conclude that competitive and cooperative receptor interactions both contribute to CheA regulation and that liposome-mediated assembly is effective in addressing these general membrane phenomena.
Asinas
Abdalin E
AE
Department of Chemistry, the University of Massachusetts, Amherst, Massachusetts 01003, USA.
Weis
Robert M
RM
D001426:Bacterial Proteins / Q000502:physiology*; D001665:Binding Sites; D001667:Binding, Competitive; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000502:physiology*; D000071677:Histidine Kinase; D007700:Kinetics; D008055:Lipids / Q000737:chemistry; D008081:Liposomes / Q000737:chemistry; D008565:Membrane Proteins / Q000502:physiology*; D000072236:Methyl-Accepting Chemotaxis Proteins; D008954:Models, Biological; D009154:Mutation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D015398:Signal Transduction
D001426:Bacterial Proteins; C489103:CheW protein, E coli; D029968:Escherichia coli Proteins; D008055:Lipids; D008081:Liposomes; D008565:Membrane Proteins; D000072236:Methyl-Accepting Chemotaxis Proteins; D000071677:Histidine Kinase; C000607608:cheA protein, E coli