title: Coupling ligand structure to specific conformational switches in the beta2-adrenoceptor.
abstract: G protein-coupled receptors (GPCRs) regulate a wide variety of physiological functions in response to structurally diverse ligands ranging from cations and small organic molecules to peptides and glycoproteins. For many GPCRs, structurally related ligands can have diverse efficacy profiles. To investigate the process of ligand binding and activation, we used fluorescence spectroscopy to study the ability of ligands having different efficacies to induce a specific conformational change in the human beta2-adrenoceptor (beta2-AR). The 'ionic lock' is a molecular switch found in rhodopsin-family GPCRs that has been proposed to link the cytoplasmic ends of transmembrane domains 3 and 6 in the inactive state. We found that most partial agonists were as effective as full agonists in disrupting the ionic lock. Our results show that disruption of this important molecular switch is necessary, but not sufficient, for full activation of the beta2-AR.
authors.affiliation: Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 279 Campus Drive, Stanford, Palo Alto, California 94305, USA.
authors.forename: Xiaojie
authors.initials: X
authors.lastname: Yao
authors.forename: Charles
authors.initials: C
authors.lastname: Parnot
authors.forename: Xavier
authors.initials: X
authors.lastname: Deupi
authors.forename: Venkata R P
authors.initials: VR
authors.lastname: Ratnala
authors.forename: Gayathri
authors.initials: G
authors.lastname: Swaminath
authors.forename: David
authors.initials: D
authors.lastname: Farrens
authors.forename: Brian
authors.initials: B
authors.lastname: Kobilka
mesh_terms: D058666:Adrenergic beta-2 Receptor Agonists; D000420:Albuterol / Q000494:pharmacology; D000526:Alprenolol / Q000494:pharmacology; D000595:Amino Acid Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray; D004837:Epinephrine / Q000494:pharmacology; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D008024:Ligands; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D011412:Propanolamines / Q000494:pharmacology; D011487:Protein Conformation / Q000187:drug effects; D017434:Protein Structure, Tertiary / Q000187:drug effects; D018343:Receptors, Adrenergic, beta-2 / Q000737:chemistry* / Q000378:metabolism*; D012680:Sensitivity and Specificity; D013050:Spectrometry, Fluorescence
chemical_list: D058666:Adrenergic beta-2 Receptor Agonists; D008024:Ligands; D011412:Propanolamines; D018343:Receptors, Adrenergic, beta-2; C026777:ICI 118551; D000526:Alprenolol; D007545:Isoproterenol; D000420:Albuterol; D004837:Epinephrine