PMID: 31072904
Warne T, Edwards PC, Dore AS, Leslie AGW, Tate CG
Molecular basis for high-affinity agonist binding in GPCRs.
Science. 2019 May 9. pii: science.aau5595. doi: 10.1126/science.aau5595.
G protein-coupled receptors (GPCRs) in the G protein-coupled active state have higher affinity for agonists compared to when they are in the inactive state, but the molecular basis for this is unclear. We have determined four active-state structures of the beta1-adrenoceptor (beta1AR) bound to conformation-specific nanobodies in the presence of agonists of varying efficacy. Comparison with inactive-state structures of beta1AR bound to the identical ligands showed a 24-42% 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.