ABSTRACT
G protein-mediated signal transduction is a fundamental mechanism of cell communication, involved in neurotransmission, responses to hormones, chemical sensation, cell growth, and cell differentiation.1,2,3 These signal transducers receive information from a large number of heptahelical cell surface receptors, and they communicate with various intracellular effectors, including adenylyl cyclases, phospholipases, and ion channels. Each heterotrimeric G protein is composed of a guanine nucleotide-binding α subunit and a high-affinity dimer of β and γsubunits. Agonist bound receptors activate G proteins to generate GTP bound α and free βγ subunits. Both of these subunits are able to regulate the activity of effectors. GTP bound to Gα is hydrolysed by its GTPase activity to GDP and GDP-a reassociates with βγ subunits to form an inactive heterotrimer.
