( chemotaxis | Monod, Wyman, and Changeux model | receptor clustering )
Departments of *Molecular Biology and Physics, Princeton University, Princeton, NJ 08544-1014; NEC Laboratories America, Inc., 4 Independence Way, Princeton, NJ 08540; and ¶Department of Physics, Ben Gurion University, Beer Sheva 84105, Israel
Edited by Stephen L. Mayo, California Institute of Technology, Pasadena, CA, and approved December 15, 2005 (received for review August 26, 2005)
The chemotaxis network in Escherichia coli is remarkable for its sensitivity to small relative changes in the concentrations of multiple chemical signals. We present a model for signal integration by mixed clusters of interacting two-state chemoreceptors. Our model results compare favorably to the results obtained by Sourjik and Berg with in vivo fluorescence resonance energy transfer. Importantly, we identify two distinct regimes of behavior, depending on the relative energies of the two states of the receptors. In regime I, coupling of receptors leads to high sensitivity, while in regime II, coupling of receptors leads to high cooperativity, i.e., high Hill coefficient. For homogeneous receptors, we predict an observable transition between regime I and regime II with increasing receptor methylation or amidation.