title: K303⁶·⁵⁸ in the μ opioid (MOP) receptor is important in conferring selectivity for covalent binding of β-funaltrexamine (β-FNA).
abstract: β-funaltrexamine (β-FNA) is an irreversible μ opioid (MOP) receptor antagonist and a reversible agonist of κ opioid (KOP) receptor. β-FNA binds covalently to the MOP receptor at Lys233(5.39), which is conserved among opioid receptors. Molecular docking of β-FNA showed that K303(6.58) in the MOP receptor and E297(6.58) in the KOP receptor played distinct roles in positioning β-FNA. K303(6.58)E MOP receptor and E297(6.58)K KOP receptor mutants were generated. The mutations did not affect β-FNA affinity or efficacy. K303(6.58)E mutation in the MOP receptor greatly reduced covalent binding of [(3)H]β-FNA; however, E297(6.58)K did not enable the KOP receptor to bind irreversibly to β-FNA. Molecular modeling demonstrated that the ε-amino group of K303(6.58) in the MOP receptor interacted with CO of the acetate group of β-FNA to facilitate covalent bond formation with Lys233(5.39). Replacement of K303(6.58) with Glu in the MOP receptor resulted in repulsion between the COOH of Glu and the CO of β-FNA and increased the distance between K233(5.39) and the fumarate group, making it impossible for covalent bond formation. These findings will be helpful for design of selective non-peptide MOP receptor antagonists.
authors.affiliation: Center for Substance Abuse Research and Department of Pharmacology, Temple University School of Medicine, 3500 N. Broad Street, MERB 851, Philadelphia, PA 19140, United States. Electronic address: kelly.dimattio@temple.edu.
authors.forename: Kelly M
authors.initials: KM
authors.lastname: DiMattio
authors.affiliation: Center for Substance Abuse Research and Department of Pharmacology, Temple University School of Medicine, 3500 N. Broad Street, MERB 851, Philadelphia, PA 19140, United States. Electronic address: cgggc@temple.edu.
authors.forename: Chongguang
authors.initials: C
authors.lastname: Chen
authors.affiliation: Department of Physiology and Biophysics, Institute for Computational Biomedicine, Weill Medical College of Cornell University, 1300 York Ave., Box 75, New York, NY 10065, United States. Electronic address: les2007@med.cornell.edu.
authors.forename: Lei
authors.initials: L
authors.lastname: Shi
authors.affiliation: Center for Substance Abuse Research and Department of Pharmacology, Temple University School of Medicine, 3500 N. Broad Street, MERB 851, Philadelphia, PA 19140, United States. Electronic address: lliuche@temple.edu.
authors.forename: Lee-Yuan
authors.initials: LY
authors.lastname: Liu-Chen
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D017124:Conserved Sequence; D005110:Extracellular Space / Q000378:metabolism; D006801:Humans; D008239:Lysine; D051379:Mice; D062105:Molecular Docking Simulation; D009154:Mutation; D009271:Naltrexone / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000378:metabolism* / Q000494:pharmacology; D011485:Protein Binding; D011487:Protein Conformation; D051381:Rats; D017473:Receptors, Opioid, kappa / Q000819:agonists / Q000378:metabolism; D017450:Receptors, Opioid, mu / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D009292:Narcotic Antagonists; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; D009271:Naltrexone; C024524:beta-funaltrexamine; D008239:Lysine
keywords: Irreversible binding; Kappa opioid receptor; Mu opioid receptor; β-funaltrexamine