Functional interactions between receptors in bacterial chemotaxis.
Bacterial chemotaxis is a model system for signal transduction, noted for its relative simplicity, high sensitivity, wide dynamic range and robustness. Changes in ligand concentrations are sensed by a protein assembly consisting of transmembrane receptors, a coupling protein (CheW) and a histidine kinase (CheA). In Escherichia coli, these components are organized at the cell poles in tight clusters that contain several thousand copies of each protein. Here we studied the effects of variation in the composition of clusters on the activity of the kinase and its sensitivity to attractant stimuli, monitoring responses in vivo using fluorescence resonance energy transfer. Our results indicate that assemblies of bacterial chemoreceptors work in a highly cooperative manner, mimicking the behaviour of allosteric proteins. Conditions that favour steep responses to attractants in mutants with homogeneous receptor populations also enhance the sensitivity of the response in wild-type cells. This is consistent with a number of models that assume long-range cooperative interactions between receptors as a general mechanism for signal integration and amplification.
Sourjik
Victor
V
Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, Massachusetts 02138, USA.
Berg
Howard C
HC
D001426:Bacterial Proteins / Q000378:metabolism; D002633:Chemotaxis; D004926:Escherichia coli / Q000166:cytology / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism*; D000071677:Histidine Kinase; D008024:Ligands; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000378:metabolism; D000072236:Methyl-Accepting Chemotaxis Proteins; D011494:Protein Kinases / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism*; D015398:Signal Transduction
D001426:Bacterial Proteins; C489103:CheW protein, E coli; D029968:Escherichia coli Proteins; D008024:Ligands; D046911:Macromolecular Substances; D008565:Membrane Proteins; D000072236:Methyl-Accepting Chemotaxis Proteins; D011956:Receptors, Cell Surface; C051236:CheW protein, Bacteria; C069656:CheB protein, Bacteria; D011494:Protein Kinases; D000071677:Histidine Kinase; C000607608:cheA protein, E coli