Okada K, Sujaku T, Chuman Y, Nakashima R, Nose T, Costa T, Yamada Y, Yokoyama M, Nagahisa A, Shimohigashi Y
Laboratory of Structure-Function Biochemistry, Kyushu University, Fukuoka, 812-8581, Japan.
Biochem Biophys Res Commun. 2000 Nov 19;278(2):493-8. doi: 10.1006/bbrc.2000.3822.
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.
神经肽孤啡肽的结构特征之一是在第8 - 9位和12 - 13位存在精氨酸 - 赖氨酸（RK）残基；这两个RK残基都被认为可与七跨膜结构域受体ORL1的第二个细胞外环中的酸性氨基酸簇结合。为了获得一种与受体酸性簇结合更强的类似物，我们采用了一种设计策略，合成了一系列孤啡肽类似物，其中RK二肽单元被置于与亲本RK相邻的第6 - 7位、10 - 11位或14 - 15位。在这些含有RK三联重复序列的孤啡肽类似物中，[精氨酸 - 赖氨酸(6 - 7)] - 和[精氨酸 - 赖氨酸(10 - 11)]孤啡肽在受体结合试验和[(35)S]GTPγS结合功能试验中均表现出较弱的活性（分别为孤啡肽活性的6 - 9%和60 - 90%）。相比之下，[精氨酸 - 赖氨酸(14 - 15)]孤啡肽在这两种试验中均表现出很强的活性（结合试验中为3倍，GTPγS功能试验中为17倍）。[精氨酸 - 赖氨酸(14 - 15)]孤啡肽是第一个被发现比亲本孤啡肽更强的肽类似物，结构 - 活性研究表明，引入的精氨酸 - 赖氨酸(14 - 15)与受体酸性氨基酸簇或受体芳香族氨基酸残基相互作用。
