title: Photolabelling the rat urotensin II/GPR14 receptor identifies a ligand-binding site in the fourth transmembrane domain.
abstract: A urotensin II (U-II) peptide analogue containing the photoreactive p -benzoyl-L-phenylalanine (Bz-Phe) in the sixth position was used to identify ligand-binding sites of the rat U-II receptor, also known as GPR14. [Bz-Phe(6)]U-II bound the receptor expressed in COS-7 cells with high affinity (IC(50) 0.7 nM) and was as potent as U-II in the agonist-induced production of inositol phosphate. Photolabelling of the U-II receptor with (125)I-[Bz-Phe(6)]U-II resulted in the specific formation of a glycosylated (125)I-[Bz-Phe(6)]U-II-U-II receptor complex of 60 kDa. Digestion of the 60 kDa complex with endoproteinase Glu-C generated a fragment of 17 kDa circumscribing the labelled fragment to residues 148-286. Digestion of the ligand-receptor complex with endoproteinase Arg-C produced a short peptide of 4 kDa corresponding to fragments 125-148, 167-192 or 210-233. CNBr treatment of the endoproteinase-Glu-C and -Arg-C fragments yielded 2 kDa fragments, defining the labelling site to methionine residues 184/185 of the fourth transmembrane domain. Photolabelling of two mutant receptors, M184L/M185L and M184A/M185A, led to a significant decrease in the overall yield of covalent labelling. Taken together, our results indicate that position 6 of U-II normally occupied by phenylalanine would interact with Met(184) and/or Met(185) of the fourth transmembrane domain of the U-II receptor. This information should be of significant value in the study of the interactions between U-II and its cognate receptor.
authors.affiliation: Department of Pharmacology, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4.
authors.forename: Antony A
authors.initials: AA
authors.lastname: Boucard
authors.forename: Simon S
authors.initials: SS
authors.lastname: Sauvé
authors.forename: Gaétan
authors.initials: G
authors.lastname: Guillemette
authors.forename: Emanuel
authors.initials: E
authors.lastname: Escher
authors.forename: Richard
authors.initials: R
authors.lastname: Leduc
mesh_terms: D000581:Amidohydrolases / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D010450:Endopeptidases / Q000378:metabolism; D006801:Humans; D008024:Ligands; D008969:Molecular Sequence Data; D043524:Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase; D019920:Photoaffinity Labels / Q000378:metabolism*; D011485:Protein Binding; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D051381:Rats; D011956:Receptors, Cell Surface / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D043562:Receptors, G-Protein-Coupled; D014579:Urotensins / Q000737:chemistry / Q000378:metabolism*
chemical_list: D008024:Ligands; D019920:Photoaffinity Labels; D020033:Protein Isoforms; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D014579:Urotensins; C473142:Uts2r protein, rat; C029677:urotensin II; D010450:Endopeptidases; D000581:Amidohydrolases; D043524:Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase