title: Structural basis for μ-opioid receptor binding and activation.
abstract: Opioids that stimulate the μ-opioid receptor (MOR1) are the most frequently prescribed and effective analgesics. Here we present a structural model of MOR1. Molecular dynamics simulations show a ligand-dependent increase in the conformational flexibility of the third intracellular loop that couples with the G protein complex. These simulations likewise identified residues that form frequent contacts with ligands. We validated the binding residues using site-directed mutagenesis coupled with radioligand binding and functional assays. The model was used to blindly screen a library of ∼1.2 million compounds. From the 34 compounds predicted to be strong binders, the top three candidates were examined using biochemical assays. One compound showed high efficacy and potency. Post hoc testing revealed this compound to be nalmefene, a potent clinically used antagonist, thus further validating the model. In summary, the MOR1 model provides a tool for elucidating the structural mechanism of ligand-initiated cell signaling and for screening novel analgesics.
authors.affiliation: Biochemistry and Biophysics Department, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
authors.forename: Adrian W R
authors.initials: AW
authors.lastname: Serohijos
authors.forename: Shuangye
authors.initials: S
authors.lastname: Yin
authors.forename: Feng
authors.initials: F
authors.lastname: Ding
authors.forename: Josee
authors.initials: J
authors.lastname: Gauthier
authors.forename: Dustin G
authors.initials: DG
authors.lastname: Gibson
authors.forename: William
authors.initials: W
authors.lastname: Maixner
authors.forename: Nikolay V
authors.initials: NV
authors.lastname: Dokholyan
authors.forename: Luda
authors.initials: L
authors.lastname: Diatchenko
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002417:Cattle; D000242:Cyclic AMP / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D016208:Databases, Factual; D049832:Decapodiformes; D004174:Diprenorphine / Q000737:chemistry / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D057809:HEK293 Cells; D006801:Humans; D056004:Molecular Dynamics Simulation; D009020:Morphine / Q000737:chemistry / Q000494:pharmacology; D016297:Mutagenesis, Site-Directed; D009271:Naltrexone / Q000031:analogs & derivatives / Q000737:chemistry / Q000494:pharmacology; D011485:Protein Binding; D011869:Radioligand Assay; D017450:Receptors, Opioid, mu / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D054852:Small Molecule Libraries
chemical_list: C485764:OPRM1 protein, human; D017450:Receptors, Opioid, mu; D054852:Small Molecule Libraries; D004174:Diprenorphine; D009271:Naltrexone; D009020:Morphine; D000242:Cyclic AMP; C038981:nalmefene
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