Fong T M, Yu H, Huang R R, Strader C D
Department of Molecular Pharmacology and Biochemistry, Merck Research Laboratories, Rahway, New Jersey 07065.
Biochemistry. 1992 Dec 1;31(47):11806-11. doi: 10.1021/bi00162a019.
The neurokinin-1 receptor binds neurokinin peptides with the potency order of substance P > substance K > neurokinin B. Elucidating the molecular basis of differential peptide selectivity will require the localization of the binding domain on the receptor. In the present report, mutagenesis and heterologous expression experiments reveal that a segment of the extracellular N-terminal sequence of the neurokinin-1 receptor is required for the high-affinity binding of substance P and related peptide agonists. Substitution of amino acid residues in the N-terminal region of the receptor affects the binding affinity of both intact peptides and a C-terminal substance P "analog", but not of a nonpeptide antagonist. Glycosylation of the receptor does not change the peptide binding affinity. In addition, substitution of the valine-97 residue in the rat neurokinin-1 receptor by a glutamate residue increases the binding affinity of neurokinin B but not substance P or substance K, suggesting that the second extracellular segment is involved in peptide selectivity. These results indicate that the extracellular domains of neurokinin-1 receptor play a critical role in peptide binding.
神经激肽-1受体与神经激肽肽段结合的效力顺序为：P物质＞K物质＞神经激肽B。阐明肽段选择性差异的分子基础需要确定受体上的结合结构域。在本报告中，诱变和异源表达实验表明，神经激肽-1受体细胞外N端序列的一段对于P物质和相关肽激动剂的高亲和力结合是必需的。受体N端区域氨基酸残基的替换会影响完整肽段和C端P物质“类似物”的结合亲和力，但不影响非肽拮抗剂的结合亲和力。受体的糖基化不会改变肽段结合亲和力。此外，将大鼠神经激肽-1受体中的缬氨酸-97残基替换为谷氨酸残基会增加神经激肽B的结合亲和力，但不会增加P物质或K物质的结合亲和力，这表明第二个细胞外区段参与了肽段选择性。这些结果表明，神经激肽-1受体的细胞外结构域在肽段结合中起关键作用。
