Molecular basis for high-affinity agonist binding in GPCRs.
Warne, T., Edwards, P.C., Dore, A.S., Leslie, A.G.W., Tate, C.G.(2019) Science 364: 775-778
- PubMed: 31072904 
- DOI: https://doi.org/10.1126/science.aau5595
- Primary Citation of Related Structures:  
6H7J, 6H7L, 6H7M, 6H7O - PubMed Abstract: 
G protein-coupled receptors (GPCRs) in the G protein-coupled active state have higher affinity for agonists as compared with when they are in the inactive state, but the molecular basis for this is unclear. We have determined four active-state structures of the β 1 -adrenoceptor (β 1 AR) bound to conformation-specific nanobodies in the presence of agonists of varying efficacy. Comparison with inactive-state structures of β 1 AR bound to the identical ligands showed a 24 to 42% reduction in the volume of the orthosteric binding site. Potential hydrogen bonds were also shorter, and there was up to a 30% increase in the number of atomic contacts between the receptor and ligand. This explains the increase in agonist affinity of GPCRs in the active state for a wide range of structurally distinct agonists.
Organizational Affiliation: 
Medical Research Council (MRC) Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK.