Heterotrimeric G protein signaling is important in a wide range of physiological processes; however, little is known about how activated heterotrimer subunits (Gαβγ) are oriented at the membrane during signal transduction. Tesmer et al. provide a snapshot of activated G proteins in a 3.1 angstrom crystal structure of G protein-coupled receptor kinase 2 (GRK2) bound simultaneously to activated Gαq and Gβγ. GRK2 is critical to the phosphorylation-dependent desensitization of many G protein-coupled receptors. In the complex, Gαq is fully dissociated from Gβγ, is oriented away from its position in the heterotrimer, and forms an effector-like interaction with GRK2.
V. M. Tesmer, T. Kawano, A. Shankaranarayanan, T. Kozasa, J. J. G. Tesmer, Snapshot of activated G proteins at the membrane: The Gαq-GRK2-Gβγ complex. Science 310, 1686-1690 (2005). [Abstract] [Full Text]