G PROTEIN βγ SUBUNITS

▪ Abstract 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 G αβγ heterotrimers, dissociate into G α and G βγ subunits that separately activate intracellular effector molecules. Only recently has the G βγ subunit been recognized as a signal transduction molecule in its own right; G βγ is now known to directly regulate as many different protein targets as the G α subunit. Recent X-ray crystallography of G α , G βγ , and G αβγ subunits will guide the investigation of structure-function relationships.