title: Modeling GPCR active state conformations: the β(2)-adrenergic receptor.
abstract: The recent publication of several G protein-coupled receptor (GPCR) structures has increased the information available for homology modeling inactive class A GPCRs. Moreover, the opsin crystal structure shows some active features. We have therefore combined information from these two sources to generate an extensively validated model of the active conformation of the β(2)-adrenergic receptor. Experimental information on fully active GPCRs from zinc binding studies, site-directed spin labeling, and other spectroscopic techniques has been used in molecular dynamics simulations. The observed conformational changes reside mainly in transmembrane helix 6 (TM6), with additional small but significant changes in TM5 and TM7. The active model has been validated by manual docking and is in agreement with a large amount of experimental work, including site-directed mutagenesis information. Virtual screening experiments show that the models are selective for β-adrenergic agonists over other GPCR ligands, for (R)- over (S)-β-hydroxy agonists and for β(2)-selective agonists over β(1)-selective agonists. The virtual screens reproduce interactions similar to those generated by manual docking. The C-terminal peptide from a model of the stimulatory G protein, readily docks into the active model in a similar manner to which the C-terminal peptide from transducin, docks into opsin, as shown in a recent opsin crystal structure. This GPCR-G protein model has been used to explain site-directed mutagenesis data on activation. The agreement with experiment suggests a robust model of an active state of the β(2)-adrenergic receptor has been produced. The methodology used here should be transferable to modeling the active state of other GPCRs.
authors.affiliation: Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, CO4 3SQ, United Kingdom.
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Simpson
authors.forename: Ian D
authors.initials: ID
authors.lastname: Wall
authors.forename: Frank E
authors.initials: FE
authors.lastname: Blaney
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Reynolds
mesh_terms: D058666:Adrenergic beta-2 Receptor Agonists / Q000494:pharmacology; D058672:Adrenergic beta-2 Receptor Antagonists / Q000494:pharmacology; D000818:Animals; D001665:Binding Sites; D020134:Catalytic Domain; D002417:Cattle; D006801:Humans; D006860:Hydrogen Bonding; D008024:Ligands; D056004:Molecular Dynamics Simulation; D016297:Mutagenesis, Site-Directed; D055355:Opsins / Q000737:chemistry; D011487:Protein Conformation; D018343:Receptors, Adrenergic, beta-2 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D015032:Zinc / Q000378:metabolism
chemical_list: D058666:Adrenergic beta-2 Receptor Agonists; D058672:Adrenergic beta-2 Receptor Antagonists; D008024:Ligands; D055355:Opsins; D018343:Receptors, Adrenergic, beta-2; D015032:Zinc