title: Synthesis, biological evaluation and structural characterization of novel glycopeptide analogues of nociceptin N/OFQ.
abstract: To examine if the biological activity of the N/OFQ peptide, which is the native ligand of the pain-related and viable drug target NOP receptor, could be modulated by glycosylation and if such effects could be conformationally related, we have synthesized three N/OFQ glycopeptide analogues, namely: [Thr(5)-O-α-D-GalNAc-N/OFQ] (glycopeptide 1), [Ser(10)-O-α-D-GalNAc]-N/OFQ (glycopeptide 2) and [Ser(10)-O-β-D-GlcNAc]-N/OFQ] (glycopeptide 3). They were tested for biological activity in competition binding assays using the zebrafish animal model in which glycopeptide 2 exhibited a slightly improved binding affinity, whereas glycopeptide 1 showed a remarkably reduced binding affinity compared to the parent compound and glycopeptide 3. The structural analysis of these glycopeptides and the parent N/OFQ peptide by NMR and circular dichroism indicated that their aqueous solutions are mainly populated by random coil conformers. However, in membrane mimic environments a certain proportion of the molecules of all these peptides exist as α-helix structures. Interestingly, under these experimental conditions, glycopeptide 1 (glycosylated at Thr-5) exhibited a population of folded hairpin-like geometries. From these facts it is tempting to speculate that nociceptin analogues showing linear helical structures are more complementary and thus interact more efficiently with the native NOP receptor than folded structures, since glycopeptide 1 showed a significantly reduced binding affinity for the NOP receptor.
authors.affiliation: Instituto de Química Avanzada de Cataluña (IQAC-CSIC), Barcelona, Spain.
authors.forename: Gemma
authors.initials: G
authors.lastname: Arsequell
authors.forename: Mònica
authors.initials: M
authors.lastname: Rosa
authors.forename: Carlos
authors.initials: C
authors.lastname: Mayato
authors.forename: Rosa L
authors.initials: RL
authors.lastname: Dorta
authors.forename: Verónica
authors.initials: V
authors.lastname: Gonzalez-Nunez
authors.forename: Katherine
authors.initials: K
authors.lastname: Barreto-Valer
authors.forename: Filipa
authors.initials: F
authors.lastname: Marcelo
authors.forename: Luis P
authors.initials: LP
authors.lastname: Calle
authors.forename: Jesús T
authors.initials: JT
authors.lastname: Vázquez
authors.forename: Raquel E
authors.initials: RE
authors.lastname: Rodríguez
authors.forename: Jesús
authors.initials: J
authors.lastname: Jiménez-Barbero
authors.forename: Gregorio
authors.initials: G
authors.lastname: Valencia
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001667:Binding, Competitive; D002460:Cell Line; D006020:Glycopeptides / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D018847:Opioid Peptides / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*; D011485:Protein Binding; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism*; D011957:Receptors, Opioid / Q000819:agonists; D015027:Zebrafish; D000097629:Nociceptin
chemical_list: D006020:Glycopeptides; D018847:Opioid Peptides; D043562:Receptors, G-Protein-Coupled; D011957:Receptors, Opioid; D000097629:Nociceptin