A regulatory domain (R1-R2) in the amino terminus of the N-methyl-D-aspartate receptor:: Effects of spermine, protons, and ifenprodil, and structural similarity to bacterial leucine/isoleucine/valine binding protein
A regulatory domain (R1-R2) in the amino terminus of the N-methyl-D-aspartate receptor:: Effects of spermine, protons, and ifenprodil, and structural similarity to bacterial leucine/isoleucine/valine binding protein
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DOI：
10.1124/mol.55.6.957
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发表时间：
1999-06-01
影响因子：
3.6
通讯作者：
Williams, K
中科院分区：
文献类型：
--
作者：
Masuko, T;Kashiwagi, K;Williams, K
精胺、质子和艾芬地尔在 N-甲基-D-天冬氨酸受体上存在复杂的相互作用。精胺刺激可能涉及质子抑制的减轻，而艾芬地尔抑制可能涉及质子抑制的增加。我们使用爪蟾卵母细胞中表达的 NR1/NR2B 受体的电压钳记录研究了 NR1 亚基中酸性残基的突变。外显子 5 插入位点附近的残基（包括 E181 和 E185）发生突变，减少了精胺刺激和质子抑制。突变NR1(D130N)使对艾芬地尔的敏感性降低了500倍以上，但对精胺和pH的敏感性影响不大。 NR1 亚基该区域的其他六个残基的突变降低了艾芬地尔的效力，在某些情况下甚至降低了艾芬地尔的最大效果。这些突变体不会影响对 pH、谷氨酸、甘氨酸或 N-甲基-D-天冬氨酸通道的其他标志特性（例如 Mg2+ 阻断和 Ba2+ 渗透性）的敏感性。该区域中的残基可能构成艾芬地尔结合位点的一部分。为了模拟 NR1 的这个区域，我们将预测的 NR1 二级结构（残基 19-400）与 1,400 个蛋白质的已知结构进行了比较。 NR1的这个区域与细菌亮氨酸/异亮氨酸/缬氨酸结合蛋白最相似，是一种含有两个长袍的球状氨基酸结合蛋白，与谷氨酸受体的下游S1-S2区域相似。我们提出NR1(22-375)的三级结构类似于亮氨酸/异亮氨酸/缬氨酸结合蛋白，包含两个“调节”结构域，我们称之为R1和R2。该区域包含精胺和艾芬地尔的结合位点，可能会影响构成甘氨酸结合袋的下游 S1 和 S2 结构域。
There are complex interactions between spermine, protons, and ifenprodil at N-methyl-D-aspartate receptors. Spermine stimulation may involve relief of proton inhibition, whereas ifenprodil inhibition may involve an increase in proton inhibition. We studied mutations at acidic residues in the NR1 subunit using voltage-clamp recording of NR1/NR2B receptors expressed in Xenopus oocytes. Mutations at residues near the site of the exon-5 insert, including E181 and E185, reduced spermine stimulation and proton inhibition. Mutation NR1(D130N) reduced sensitivity to ifenprodil by more than 500-fold, but had little effect on sensitivity to spermine and pH. Mutations at six other residues in this region of the NR1 subunit reduced the potency and, in some cases, the maximum effect of ifenprodil. These mutants did not affect sensitivity to pH, glutamate, glycine, or other hallmark properties of N-methyl-D-aspartate channels such as Mg2+ block and Ba2+ permeability. Residues in this region presumably form part of the ifenprodil-binding site. To model this region of NR1 we compared the predicted secondary structure of NR1 (residues 19-400) with the known structures of 1,400 proteins. This region of NR1 is most similar to bacterial leucine/isoleucine/valine binding protein, a globular amino acid binding protein containing two robes, similar to the downstream S1-S2 region of glutamate receptors. We propose that the tertiary structure of NR1(22-375) is similar to leucine/isoleucine/valine binding protein, containing two "regulatory" domains, which we term R1 and R2. This region, which contains the binding sites for spermine and ifenprodil, may influence the downstream S1 and S2 domains that constitute the glycine binding pocket.