Fong T M, Huang R R, Strader C D
Department of Molecular Pharmacology and Biochemistry, Merck Research Laboratories, Rahway, New Jersey 07065.
J Biol Chem. 1992 Dec 25;267(36):25664-7.
To identify the molecular determinants of ligand-receptor interactions, the extracellular domain of the human neurokinin-1 receptor was systematically substituted with the corresponding sequences from the other two neurokinin receptor subtypes. Three residues within the first extracellular segment and 2 residues of the second segment are required for the optimal binding of all three natural peptide agonists. The divergent nature of 4 of the 5 residues supports the hypothesis that the peptide binding site on the neurokinin-1 receptor is not highly conserved in the other two receptor subtypes. In contrast, substitution of part of the third extracellular segment and the fourth extracellular segment with the corresponding amino acids of the human neurokinin-3 receptor results in an increase in neurokinin B affinity without affecting substance P binding, suggesting that the two peptides do not interact with the same set of functional groups on the receptor. Among the four extracellular regions, only parts of the third and fourth segments affect the binding of the quinuclidine antagonist L-703,606, and these two regions may partially account for the neurokinin-1 receptor subtype specificity of this non-peptide antagonist. These studies demonstrate that both the extracellular and transmembrane domains of the neurokinin-1 receptor are involved in the binding of substance P and related peptides.
为了确定配体 - 受体相互作用的分子决定因素，人神经激肽 -1 受体的胞外结构域被系统地替换为来自其他两种神经激肽受体亚型的相应序列。所有三种天然肽激动剂的最佳结合需要第一个胞外段内的三个残基和第二个段的两个残基。五个残基中的四个的不同性质支持这样的假设，即神经激肽 -1 受体上的肽结合位点在其他两种受体亚型中不是高度保守的。相反，用人神经激肽 -3 受体的相应氨基酸替换第三胞外段和第四胞外段的一部分会导致神经激肽 B 亲和力增加，而不影响 P 物质的结合，这表明这两种肽与受体上不同的功能基团相互作用。在四个胞外区域中，只有第三和第四段的部分影响奎宁环拮抗剂 L - 703,606 的结合，并且这两个区域可能部分解释了这种非肽拮抗剂的神经激肽 -1 受体亚型特异性。这些研究表明，神经激肽 -1 受体的胞外和跨膜结构域都参与了 P 物质和相关肽的结合。
