In unstimulated cells, the state of G alpha (orange circles) is defined by its interaction with GDP, G beta-gamma (purple circles), and a G-protein-coupled receptor (GPCR; light green loops).

followed by the dissociation of Gα-GTP from the complex. The activated subunit Gα can couple to downstream effectors to regulate the amounts of second messengers. Classically, each GPCR can ...