G proteins function by binding to guanosine triphosphate (GTP) and guanosine diphosphate (GDP). When a signaling molecule binds to a GPCR, the receptor undergoes a conformational change that activates the G protein. The G protein then exchanges GDP for GTP, becoming active. This active G protein can then go on to activate or inhibit other molecules within the cell, such as enzymes or ion channels, thereby propagating the signal.
