Crystal structure of the β2 adrenergic receptor–Gs protein complex

Abstract

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 signaling is the activation of a heterotrimeric GTP binding protein (G protein) by an agonist-occupied receptor. The β2 adrenergic receptor (β2AR) activation of Gs, the stimulatory G protein for adenylyl cyclase, has long been a model system for GPCR signaling. Here we present the crystal structure of the active state ternary complex composed of agonist-occupied monomeric β2AR and nucleotide-free Gs heterotrimer. The principal interactions between the β2AR and Gs involve the amino and carboxyl terminal α-helices of Gs, with conformational changes propagating to the nucleotide-binding pocket. The largest conformational changes in the β2AR include a 14 Å outward movement at the cytoplasmic end of transmembrane segment 6 (TM6) and an alpha helical extension of the cytoplasmic end of TM5. The most surprising observation is a major displacement of the alpha helical domain of Gαs relative to the ras-like GTPase domain. This crystal structure represents the first high-resolution view of transmembrane signaling by a GPCR.

Identification of a G-Protein Subunit-α11 Gain-of-Function Mutation, Val340Met, in a Family With Autosomal Dominant Hypocalcemia Type 2 (ADH2)

“…The α5 helix is located at the C‐terminus of Gα‐subunits and plays a critical role in GPCR binding and G‐protein activation 23, 24. Indeed, the C‐terminal portion of the α5 helix, which is known as the interface module, directly binds to the transmembrane domain and intracellular loops of activated GPCRs,24 whereas the N‐terminal portion, which is known as the transmission module, interacts with the GTPase domain β‐sheet, comprising the β1‐β6 strands (Fig. 3 C ), to mediate conformational changes in Gα‐subunit structure that facilitate guanine nucleotide exchange 23, 25.…”

“…The Phe341Leu mutation is predicted to affect the hydrophobic cluster,3 thereby leading to GDP/GTP exchange and G‐protein activation. In contrast to these roles of Phe341, the neighboring Val340 residue does not bind to activated GPCRs and is not involved in GDP/GTP exchange,24, 25 but instead may play a role in stabilizing the nucleotide‐free conformation of the Gα‐subunit once bound to activated GPCR 23. Thus, the Val340Met mutation likely mediates Gα 11 activation by influencing the stability of Gα‐GPCR interactions.…”

Cryo-EM structure of the activated GLP-1 receptor in complex with a G protein

“…Thus, the N-terminus of GLP-1 penetrates into the receptor core (Fig. 2a) to a depth comparable to the orthosteric agonist BI-167107 in the structure of activated β2AR 16 , a family A GPCR (Fig. S9b).…”

“…4a–b). Compared to the β2AR-Gs crystal structure 16 , the interface of Gs with GLP-1R additionally involves direct interactions of Gβ with ICL1 and α-helix H8, which is tilted towards the G protein (Fig. 4c–d, Fig.…”

“…Nevertheless, high resolution cryo-EM on asymmetric and relatively small membrane proteins (<200 kDa) remains challenging due to the low signal-to-noise ratio that hampers the accuracy of angular determination for 3D reconstructions. This problem is compounded by the intrinsically dynamic character of the 7TM bundle 14, 15 and the relative instability of GPCR complexes, such as with G proteins 16 or arrestins 17 , often resulting in conformational variability or even dissociation during cryo-EM specimen preparation. Notwithstanding these challenges, cryo-EM visualization for GPCR complexes holds tremendous potential for uncovering the various molecular mechanisms involved in signal transduction and regulation of GPCRs and their effector proteins.…”