G protein signaling: insights from new structures.

A large body of experimental evidence exists that links heterotrimeric guanosine triphosphate-binding protein (G protein) structure to function. The determination of the crystal structures of G proteins in various activational states and, more recently, in complexes with effectors and other signaling partners highlights the varied mechanisms involved in G protein regulation. Signaling complexes, such as the recently solved complex of Gbetagamma and G protein receptor kinase 2 (GRK2), provide new insights into the mechanisms underlying the regulation of these highly conserved signaling molecules. In this Review, we discuss the latest findings and their implications for G protein-signaling paradigms.