title: Structural requirements of nociceptin antagonist Ac-RYYRIK-NH2 for receptor binding.
abstract: Ac-RYYRIK-NH2 is a peptide isolated from the peptide library as an antagonist that inhibits the biological activities of nociceptin, a hyperalgesic neuropeptide. In order to clarify the structural requirements of this peptide for binding to the nociceptin receptor ORL1, systematic structure-activity studies were carried out. The result of Ala-scanning indicated that the N-terminal tripeptide RYY(= Arg-Tyr-Tyr) is crucially important for binding to the ORL1 receptor. Residual truncations from the N- or C-terminus revealed the special importance of the N-terminal Arg residue. The removal of protecting groups indicated that the N-terminal acetyl group is essential, but the C-terminal amide group is insignificant. These results indicated the conspicuous importance of acetyl-Arg at position 1 of Ac-RYYRIK-NH2 as a key structure allowing binding to the receptor. To investigate the binding site of this peptide in the ORL1 receptor, we synthesized and assayed a series of analogues of the nociceptin dibasic repeat region, residues 8-13 of RKSARK. None of the derivatives were active. Ac-RYYRIK-NH2 was inactive for the mu opioid receptor to which nociceptin binds with considerable strength. All the results suggested that the mode of binding between Ac-RYYRIK-NH2 and the ORL1 receptor is different to that between the ORL1 receptor and nociceptin, and that it may consist of interaction with the receptor site to which nociceptin(1-7) or -(14-17) binds.
authors.affiliation: Laboratory of Structure-Function Biochemistry, Faculty and Graduate School of Sciences, Kyushu University, Fukuoka 812-8581, Japan.
authors.forename: Chiaki
authors.initials: C
authors.lastname: Kawano
authors.forename: Kazushi
authors.initials: K
authors.lastname: Okada
authors.forename: Takeshi
authors.initials: T
authors.lastname: Honda
authors.forename: Takeru
authors.initials: T
authors.lastname: Nose
authors.forename: Kazuyasu
authors.initials: K
authors.lastname: Sakaguchi
authors.forename: Tommaso
authors.initials: T
authors.lastname: Costa
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Shimohigashi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D008969:Molecular Sequence Data; D015394:Molecular Structure; D018847:Opioid Peptides / Q000037:antagonists & inhibitors*; D010455:Peptides / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D011957:Receptors, Opioid / Q000378:metabolism*; D013329:Structure-Activity Relationship; D000094942:Nociceptin Receptor; D000097629:Nociceptin
chemical_list: D018847:Opioid Peptides; D010455:Peptides; D011957:Receptors, Opioid; D000094942:Nociceptin Receptor; D000097629:Nociceptin