ABSTRACT
The precise response of a cellular physiology to specific agents in the environment is mediated by transduction of signals across the plasma membrane. The specific signals are ligands of a variety of types-small chemical entities, peptides, or proteins-and their presence in the extracellular environment is recognized by their binding to highly specialized receptor proteins embedded in the membrane. Receptors in one superfamily, the G-proteincoupled receptors (GPCRs), respond to a very wide diversity of signaling agents. Through the binding of the signal on the extracellular side of the membrane, GPCRs undergo a conformational change that modifies their interaction with intracellular G-proteins at the membrane and leads to a cascade of additional signaling events within the cell.
