title: Conformation of ligands bound to the muscarinic acetylcholine receptor.
abstract: Many biogenic amines evoke a variety of physiological responses by acting on G protein-coupled receptors. We have determined the conformation of two acetylcholine analogs, (S)-methacholine and (2S,4R,5S)-muscarine, bound to the M(2) muscarinic acetylcholine receptor (M(2) mAChR) by NMR spectroscopy. The analysis of the transferred nuclear Overhauser effect indicated that the receptor selectively recognized the conformers of (S)-methacholine and (2S,4R,5S)-muscarine with the gauche O-C2-C1-N dihedral angle at +60 degrees. This is distinct from the predominant conformations of these ligands in solution with O-C2-C1-N dihedral angle (+80 to approximately 85 degrees ) in the absence of the M(2) mAChR, as assessed by analyses of the coupling constants and nuclear Overhauser effect spectroscopy. We have also built a molecular model of the M(2) mAChR-(S)-methacholine complex, based on the X-ray crystallographic structure of rhodopsin. This model indicated that the conformation with the gauche O-C2-C1-N dihedral angle at +55.5 degrees, which is similar to the one determined by NMR measurement, is energetically favored in the binding of (S)-methacholine to the receptor. We suggest that this conformation represents the binding of the agonist to the M(2) mAChR in the absence of G protein.
authors.affiliation: Department of Neurochemistry, Faculty of Medicine, the University of Tokyo, Tokyo, Japan.
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Furukawa
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Hamada
authors.forename: Mariko K
authors.initials: MK
authors.lastname: Hayashi
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Haga
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Muto
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hirota
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Yokoyama
authors.forename: Kazuo
authors.initials: K
authors.lastname: Nagasawa
authors.forename: Masaji
authors.initials: M
authors.lastname: Ishiguro
mesh_terms: D000818:Animals; D001665:Binding Sites; D002478:Cells, Cultured; D019204:GTP-Binding Proteins / Q000378:metabolism; D007313:Insecta; D016210:Methacholine Chloride / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D008968:Molecular Conformation; D009116:Muscarine / Q000737:chemistry / Q000378:metabolism*; D018721:Muscarinic Agonists / Q000737:chemistry / Q000378:metabolism*; D009154:Mutation; D043585:Receptor, Muscarinic M2; D011976:Receptors, Muscarinic / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: D018721:Muscarinic Agonists; D043585:Receptor, Muscarinic M2; D011976:Receptors, Muscarinic; D016210:Methacholine Chloride; D009116:Muscarine; D019204:GTP-Binding Proteins