G proteins are activated by G protein-coupled receptors (GPCRs), which are the largest class of cell surface receptors. Upon activation, they bind to guanosine triphosphate (GTP) and dissociate into subunits, which then interact with other intracellular signaling pathways. The deactivation occurs when the GTP is hydrolyzed to guanosine diphosphate (GDP), leading to the reformation of the inactive G protein complex.
