Novel, Potent ORL-1 Receptor Agonist Peptides Containing α-Helix-Promoting Conformational Constraints

摘要: The ORL-1 receptor has recently been cloned and is implicated in a wide variety of physiological pathophysiological processes. Toward the goal elucidating important features receptor-bound conformation endogenous ligand, nociceptin (NC), several conformationally constrained analogues were prepared. Either alpha-aminoisobutyric acid (Aib) or N-methylalanine (MeAla) inserted as replacement(s) for Ala7, Ala11, Ala15 native NC sequence (FGGFTGARKSARKLANQ). In vitro assays measuring human affinity (competition binding against [3H] NC), functional potency ([35S]GTP gamma S), efficacy (as compared to NC) performed each new peptide. affinities Aib-containing peptides generally matched NC, showing K(i)'s range 0.1-0.5 nM. By comparison, MeAla-containing significantly diminished. Peptide 14 (FGGFTG[Aib]RKS[Aib]RKLANQ-NH2), which contains two alanine residues (positions 7 11) C-terminal amide modification, was found be very potent agonist with K(i) = 0.05 nM EC50 0.08 assays. data support hypothesis that form might adopt an amphipathic helix "address" segment sequence.