title: Description of the low-affinity interaction between nociceptin and the second extracellular loop of its receptor by fluorescence and NMR spectroscopies.
abstract: The second extracellular loop (ECL2) of the Noc receptor has been proposed to be involved in ligand binding and selectivity. The interaction of Noc with a constrained cyclic synthetic peptide, mimicking the ECL2, has been studied using fluorescence and NMR spectroscopies. Selective binding was shown with a dissociation constant of approximately 10 microM (observed with the constrained cyclic loop and not with the open chain), and residues involved in ligand binding and selectivity have been identified. This bimolecular complex is stabilized by (i) ionic interactions between the two Noc basic motives and the ECL2 acidic residues; (ii) hydrophobic contacts involving Noc FGGF N-terminal sequence and an ECL2 tryptophane residue. Our data confirm that Noc receptor's ECL2 contributes actively to ligand binding and selectivity by providing the peptidic ligand with a low affinity-binding site.
authors.affiliation: Université de Toulouse, Institute of Pharmacology and Structural Biology, IPBS, UPS, 31077, Toulouse, France.
authors.forename: Bruno
authors.initials: B
authors.lastname: Vincent
authors.forename: Lionel
authors.initials: L
authors.lastname: Mouledous
authors.forename: Brice
authors.initials: B
authors.lastname: Bes
authors.forename: Honore
authors.initials: H
authors.lastname: Mazarguil
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Meunier
authors.forename: Alain
authors.initials: A
authors.lastname: Milon
authors.forename: Pascal
authors.initials: P
authors.lastname: Demange
mesh_terms: D002462:Cell Membrane / Q000378:metabolism; D004399:Dynorphins / Q000737:chemistry; D006801:Humans; D007477:Ions; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008856:Microscopy, Fluorescence / Q000379:methods*; D009479:Neuropeptides / Q000737:chemistry; D018847:Opioid Peptides / Q000737:chemistry; D010455:Peptides / Q000737:chemistry; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D043562:Receptors, G-Protein-Coupled / Q000737:chemistry; D011957:Receptors, Opioid / Q000737:chemistry; D013050:Spectrometry, Fluorescence / Q000379:methods; D000097629:Nociceptin
chemical_list: D004399:Dynorphins; D007477:Ions; D008024:Ligands; D009479:Neuropeptides; D018847:Opioid Peptides; D010455:Peptides; D043562:Receptors, G-Protein-Coupled; D011957:Receptors, Opioid; D000097629:Nociceptin