G protein-coupled receptors (GPCRs) are responsible for the majority of cellular responses to hormones and neurotransmitters as well as the senses of sight, olfaction and taste. The paradigm of GPCR signalling is the activation of a heterotrimeric GTP binding protein (G protein) by an agonist-occupied receptor. The β
2
adrenergic receptor (β
2
AR) activation of Gs, the stimulatory G protein for adenylyl cyclase, has long been a model system for GPCR signalling. Here we present the crystal structure of the active state ternary complex composed of agonist-occupied monomeric β
2
AR and nucleotide-free Gs heterotrimer. The principal interactions between the β
2
AR and Gs involve the amino- and carboxy-terminal α-helices of Gs, with conformational changes propagating to the nucleotide-binding pocket. The largest conformational changes in the β
2
AR include a 14 Å outward movement at the cytoplasmic end of transmembrane segment 6 (TM6) and an α-helical extension of the cytoplasmic end of TM5. The most surprising observation is a major displacement of the α-helical domain of Gαs relative to the Ras-like GTPase domain. This crystal structure represents the first high-resolution view of transmembrane signalling by a GPCR.
X-ray structure of a GPCR complex
G-protein-coupled receptors (GPCRs) mediate the majority of a cell's responses to hormones and neurotransmitters, and to the senses of sight, olfaction and taste. This makes GPCRs potentially the most important group of drug targets in the human body. GPCRs are deeply embedded in the cell membrane, crossing it seven times, so structure determination for these complexes is particularly challenging — as recounted in a recent News Feature (see
http://go.nature.com/ftqnx4
). The eagerly-awaited X-ray crystal structure of a GPCR transmembrane signalling complex has now been determined by Brian Kobilka's group. The structure presented is of an agonist-occupied monomer of the β
2
adrenergic receptor in complex with G
s
, the stimulatory G protein for adenylyl cyclase. An accompanying paper reports t...

Crystal structure of the β2 adrenergic receptor–Gs protein complex

10.1038/nature10361