Highly potent nociceptin analog containing the Arg-Lys triple repeat.
One of the structural characteristics of a neuropeptide nociceptin is the existence of Arg-Lys (RK) residues at positions 8-9 and 12-13; both RKs have been suggested to bind to the acidic amino acid cluster in the second extracellular loop of the seven transmembrane domain receptor ORL1. With a design strategy of attempting to obtain an analog that binds more strongly to the receptor's acidic cluster, we synthesized a series of nociceptin analogs in which the RK dipeptide unit was placed at positions 6-7, 10-11, or 14-15 adjacent to the parent RKs. Among these nociceptin analogs containing the RK triple repeat, [Arg-Lys(6-7)]- and [Arg-Lys(10-11)]nociceptins exhibited weak activities (6-9 and 60-90% of nociceptin, respectively) both in the receptor binding assay and in the [(35)S]GTPgammaS binding functional assay. In contrast, [Arg-Lys(14-15)]nociceptin was found to be very potent in both assays (3-fold in binding and 17-fold in GTPgammaS functional assay). [Arg-Lys(14-15)]nociceptin was the first peptide analog found to be stronger than the parent nociceptin, and structure-activity studies have suggested that the incorporated Arg-Lys(14-15) interacts with either the receptor acidic amino acid cluster or the receptor aromatic amino acid residues.
Okada
K
K
Laboratory of Structure-Function Biochemistry, Kyushu University, Fukuoka, 812-8581, Japan.
Sujaku
T
T
Chuman
Y
Y
Nakashima
R
R
Nose
T
T
Costa
T
T
Yamada
Y
Y
Yokoyama
M
M
Nagahisa
A
A
Shimohigashi
Y
Y
D000595:Amino Acid Sequence; D001120:Arginine / Q000737:chemistry*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D008239:Lysine / Q000737:chemistry*; D008969:Molecular Sequence Data; D018847:Opioid Peptides / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D011485:Protein Binding; D020449:Repetitive Sequences, Amino Acid; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship; D000097629:Nociceptin
D001120:Arginine; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D008239:Lysine; D018847:Opioid Peptides; D000097629:Nociceptin