Heightened sensitivity of a lattice of membrane receptors

Receptor proteins in both eukaryotic and prokaryotic cells have been found to form two-dimensional clusters in the plasma membrane. In this study, we examine the proposition that such clusters might show coordinated responses because of the spread of conformational states from one receptor to its ne ighbors. A Monte Carlo simulation was developed in which receptors flipped in probabilistic fashion between an active and an inactive state. Conformat ional energies depended on (i) ligand binding, (ii) a chemical modification of the receptor conferring adaptation, and (iii) the activity of neighbori ng receptors. Rate constants were based on data from known biological recep tors, especially the bacterial Tar receptor, and on theoretical constraints derived from an analogous Ising model. The simulated system showed a great ly enhanced sensitivity to external signals compared with a corresponding s et of uncoupled receptors and was operational over a much wider range of am bient concentrations. These and other properties should make a lattice of c onformationally coupled receptors ideally suited to act as a "nose" by whic h a cell can detect and respond to extracellular stimuli.