title: The importance of valine 114 in ligand binding in beta(2)-adrenergic receptor.
abstract: G-protein coupled receptors (GPCRs) are transmembrane signaling molecules, with a majority of them performing important physiological roles. beta(2)-Adrenergic receptor (beta(2)-AR) is a well-studied GPCRs that mediates natural responses to the hormones adrenaline and noradrenaline. Analysis of the ligand-binding region of beta(2)-AR using the recently solved high-resolution crystal structures revealed a number of highly conserved amino acids that might be involved in ligand binding. However, detailed structure-function studies on some of these residues have not been performed, and their role in ligand binding remains to be elucidated. In this study, we have investigated the structural and functional role of a highly conserved residue valine 114, in hamster beta(2)-AR by site-directed mutagenesis. We replaced V114 in hamster beta(2)-AR with a number of amino acid residues carrying different functional groups. In addition to the complementary substitutions V114I and V114L, the V114C and V114E mutants also showed significant ligand binding and agonist dependent G-protein activation. However, the V114G, V114T, V114S, and V114W mutants failed to bind ligand in a specific manner. Molecular modeling studies were conducted to interpret these results in structural terms. We propose that the replacement of V114 influences not only the interaction of the ethanolamine side-chains but also the aryl-ring of the ligands tested. Results from this study show that the size and orientation of the hydrophobic residue at position V114 in beta(2)-AR affect binding of both agonists and antagonists, but it does not influence the receptor expression or folding.
authors.affiliation: Department of Oral Biology, University of Manitoba, Winnipeg, Manitoba, Canada R3E 0W4.
authors.forename: Makoto
authors.initials: M
authors.lastname: Arakawa
authors.forename: Naveena
authors.initials: N
authors.lastname: Yanamala
authors.forename: Jasbir
authors.initials: J
authors.lastname: Upadhyaya
authors.forename: Andrew
authors.initials: A
authors.lastname: Halayko
authors.forename: Judith
authors.initials: J
authors.lastname: Klein-Seetharaman
authors.forename: Prashen
authors.initials: P
authors.lastname: Chelikani
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000526:Alprenolol / Q000494:pharmacology; D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D002522:Chlorocebus aethiops; D006224:Cricetinae; D000242:Cyclic AMP / Q000378:metabolism; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding / Q000187:drug effects; D018343:Receptors, Adrenergic, beta-2 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D014633:Valine / Q000737:chemistry* / Q000378:metabolism
chemical_list: D000319:Adrenergic beta-Antagonists; D018343:Receptors, Adrenergic, beta-2; D000526:Alprenolol; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D014633:Valine