G PROTEIN βγ SUBUNITS

Guanine nucleotide binding (G) proteins relay extracellular signals encoded in light, small molecules, peptides, and proteins to activate or inhibit intracellular enzymes and ion channels. The larger G proteins, made up of Gαβγ heterotrimers, dissociate into Gα and Gβγ subunits that separately activate intracellular effector molecules. Only recently has the Gβγ subunit been recognized as a signal transduction molecule in its own right; Gβγ is now known to directly regulate as many different protein targets as the Gα subunit. Recent X-ray crystallography of Gα, Gβγ, and Gαβγ subunits will guide the investigation of structure-function relationships.