Wafford K A, Kathoria M, Bain C J, Marshall G, Le Bourdellès B, Kemp J A, Whiting P J
Neuroscience Research Centre, Merck Sharp & Dohme Research Laboratories, Harlow, Essex, UK.
Mol Pharmacol. 1995 Feb;47(2):374-80.
The mammalian N-methyl-D-aspartate (NMDA) receptor complex is though to consist of an NR1 subunit in combination with one or more of the four NR2 subunits (A, B, C, and D). When corresponding cDNAs are expressed in Xenopus oocytes, ion channels with the characteristic profile of NMDA receptors are formed. The receptor is unique in requiring two coagonists, glutamate and glycine, for activation of the channel. We have used site-directed mutagenesis to study amino acids in the human NR1 subunit that contribute to the glycine binding site of the NMDA receptor without affecting the agonist site for glutamate. Mutations to D481 and K483 produced receptors with up to 160-fold lower affinities for glycine, as well as other agonists and partial agonists, without affecting maximum current size or the degree of agonist efficacy. The D481A mutation also led to 40-50-fold lower affinities for two structurally diverse glycine site antagonists. From these data we propose that the carboxyl group of this aspartate interacts with the amino moiety of glycine and the equivalent group contained in other agonists and antagonists.
哺乳动物的N-甲基-D-天冬氨酸（NMDA）受体复合物被认为由一个NR1亚基与四个NR2亚基（A、B、C和D）中的一个或多个组合而成。当相应的cDNA在非洲爪蟾卵母细胞中表达时，会形成具有NMDA受体特征性电流的离子通道。该受体的独特之处在于需要两种协同激动剂——谷氨酸和甘氨酸来激活通道。我们利用定点诱变技术研究了人类NR1亚基中对NMDA受体甘氨酸结合位点有贡献但不影响谷氨酸激动剂位点的氨基酸。D481和K483位点的突变产生了对甘氨酸以及其他激动剂和部分激动剂亲和力降低多达160倍的受体，同时不影响最大电流大小或激动剂效能程度。D481A突变还导致对两种结构不同的甘氨酸位点拮抗剂的亲和力降低40 - 50倍。根据这些数据，我们推测该天冬氨酸的羧基与甘氨酸的氨基部分以及其他激动剂和拮抗剂中所含的等效基团相互作用。
