Module 2: Figure G protein binary switching
Signal transduction through G protein binary switching.
All GTP-binding proteins (G proteins) function through a binary switching mechanism that is driven by the binding of GTP. The G protein is inactive when bound to GDP. When this GDP is exchanged for GTP, the G protein is activated and can stimulate a number of different signalling responses. The rapid switching to the active state is facilitated by the guanine nucleotide exchange factors (GEFs) that receive the information coming in from the receptors on the cell surface. By contrast, the GTPase-activating proteins (GAPs) accelerate the OFF reaction by enhancing the hydrolysis of GTP to GDP.