Crystal structure of oligomeric beta-1-adrenergic G protein-coupled receptors in ligand-free basal state.
Huang, J., Chen, S., Zhang, J.J., Huang, X.Y.(2013) Nat Struct Mol Biol 20: 419-425
- PubMed: 23435379 
- DOI: https://doi.org/10.1038/nsmb.2504
- Primary Citation of Related Structures:  
4GPO - PubMed Abstract: 
G protein-coupled receptors (GPCRs) mediate transmembrane signaling. Before ligand binding, GPCRs exist in a basal state. Crystal structures of several GPCRs bound with antagonists or agonists have been solved. However, the crystal structure of the ligand-free basal state of a GPCR, the starting point of GPCR activation and function, had not yet been determined. Here we report the X-ray crystal structure of the ligand-free basal state of a GPCR in a lipid membrane-like environment. Oligomeric turkey β1-adrenergic receptors display two dimer interfaces. One interface involves the transmembrane domain (TM) 1, TM2, the C-terminal H8 and extracellular loop 1. The other interface engages residues from TM4, TM5, intracellular loop 2 and extracellular loop 2. Structural comparisons show that this ligand-free state is in an inactive conformation. This provides the structural basis of GPCR dimerization and oligomerization.
Organizational Affiliation: 
Department of Physiology and Biophysics, Cornell University Weill Medical College, New York, New York, USA.