SIGNALING COMPLEXES - BIOPHYSICAL CONSTRAINTS ON INTRACELLULAR COMMUNICATION

This review surveys the kinds of protein complex that participate in c ell communication and identifies, where possible, general principles b y which they form and act. It also advances the notion that biophysica l constraints imposed by macromolecular crowding and diffusion have ha d a controlling influence on the evolution of cell signaling pathways. Complexes associated with the bacterial aspartate receptor, with euca ryotic tyrosine kinase receptors, with T-cell receptors, and with foca l contacts are examined together with proteins that serve as adaptors, anchors, and scaffolds for signaling complexes. The importance of dif fusion in controlling the numbers and locations of signaling complexes is discussed, as is the special role played by membranes in signaling pathways.