Heptahelical receptors are coupled to heterotrimeric GTP-binding proteins (G proteins) which transduce most signals through their alpha and betagamma subunits to effectors including adenylylcyclases, ion channels, phospholipases Cbeta, and phosphoinositide 3-kinases. The diversity of G proteins, their effectors and regulators (RGS proteins), supports the interest of these protein families as potential drug targets.