Journal Article

Phase-plate cryo-EM structure of a class B GPCR–G-protein complex

Christopoulos, Arthur, Tarrasch, Jeffrey, Miller, Laurence J., Baumeister, Wolfgang, Khoshouei, Maryam, Coudrat, Thomas, Liang, Yi-Lynn, Glukhova, Alisa, Sexton, Patrick M., Danev, Radostin, Wootten, Denise, Thal, David M., Kobilka, Brian K., Radjainia, Mazdak, Christopoulos, George, Furness, Sebastian G. B., Zhang, Yan, Skiniotis, Georgios

2017

Overview

Class B G-protein-coupled receptors are major targets for the treatment of chronic diseases, such as osteoporosis, diabetes and obesity. Here we report the structure of a full-length class B receptor, the calcitonin receptor, in complex with peptide ligand and heterotrimeric Gα s βγ protein determined by Volta phase-plate single-particle cryo-electron microscopy. The peptide agonist engages the receptor by binding to an extended hydrophobic pocket facilitated by the large outward movement of the extracellular ends of transmembrane helices 6 and 7. This conformation is accompanied by a 60° kink in helix 6 and a large outward movement of the intracellular end of this helix, opening the bundle to accommodate interactions with the α5-helix of Gα s . Also observed is an extended intracellular helix 8 that contributes to both receptor stability and functional G-protein coupling via an interaction with the Gβ subunit. This structure provides a new framework for understanding G-protein-coupled receptor function. Volta phase-plate cryo-electron microscopy reveals the structure of the full-length calcitonin receptor in complex with its peptide ligand and Gα s βγ. GPCR structure solved by cryo-electron microscopy The use of cryo-electron microscopy (cryo-EM) in structural biology has exploded in recent years as it provides structural information at near atomic resolution without the need for crystallization. However, cryo-EM has typically been limited to proteins larger than 200 kDa because of issues with low contrast. Patrick Sexton and colleagues report the structure of the full-length calcitonin receptor in complex with its peptide ligand and Gα s βγ protein by Volta phase-plate single-particle cryo-EM. This is the first G-protein-coupled receptor (GPCR) structure to be solved at high resolution by cryo-EM, the first full-length class B GPCR reported and only the second in complex with the full heterotrimeric G protein. The structure shows the GPCR in the active state and reveals key information about the conformational changes associated with peptide agonist binding and G-protein coupling in class B receptors.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 631/154/436/2387 / 631/535/1258/1259 / Binding Sites / Biomedical materials / Calcitonin / Cell Membrane - metabolism / Chronic illnesses / Conserved Sequence / Coordination compounds / Cryoelectron Microscopy / Diabetes mellitus / Electron microscopy / Functional anatomy / G protein-coupled receptors / Guanine nucleotide-binding protein / Helices / Heterotrimeric GTP-Binding Proteins - chemistry / Heterotrimeric GTP-Binding Proteins - metabolism / Heterotrimeric GTP-Binding Proteins - ultrastructure / Humanities and Social Sciences / Humans / Hydrophobic and Hydrophilic Interactions / Hydrophobicity / Intracellular / Ligands / Models, Molecular / Molecular biology / Molecular structure / multidisciplinary / Obesity / Osteoporosis / Peptides / Phase plates / Protein Conformation / Proteins / Receptors / Receptors, Calcitonin - agonists / Receptors, Calcitonin - classification / Receptors, Calcitonin - metabolism / Receptors, Calcitonin - ultrastructure / Science