The second extracellular loop of the dopamine D2 receptor lines the binding-site crevice
The second extracellular loop of the dopamine D2 receptor lines the binding-site crevice
复制标题
DOI：
10.1073/pnas.2237265100
复制
发表时间：
2004-01-13
影响因子：
11.1
通讯作者：
Javitch, JA
中科院分区：
文献类型：
--
作者：
Shi, L;Javitch, JA
多巴胺D-2受体（D2 R）的结合位点，与结合小分子的同源视紫红质样G蛋白偶联受体（GPCR）的结合位点一样，包含在其七个跨膜片段（TM）之间形成的水可进入的缝隙中。然而，牛视紫红质的高分辨率结构显示，连接TM 4和TMS的第二个细胞外环（E2）向下折叠成跨膜结构域，并形成视网膜配体结合表面的一部分。E2是否在其他视紫红质样GPCR中发挥相关作用尚不清楚。为了解决这个问题，我们现在已经突变为半胱氨酸，一次一个，D2 R的E2中的10个连续残基。这些突变体中的5个与巯基试剂的反应抑制拮抗剂结合，结合拮抗剂保护两个，I184 C和N186 C，从反应。在E2中的可访问性的模式是一致的，与牛视紫红质的结构相似，其中保守的二硫键的C-末端的区域是更深的结合位点的裂缝比N-末端部分的E2。因此，E2可能有助于D2 R中的结合位点，也可能有助于其他胺能GPCR中的结合位点。了解GPCR分子的详细定位及其与配体的相互作用，将有助于GPCR分子模拟和新药设计。
The binding site of the dopamine D-2 receptor (D2R), like those of homologous rhodopsin-like G protein-coupled receptors (GPCRs) that bind small molecules, is contained within a water-accessible crevice formed among its seven transmembrane segments (TMs). The high-resolution structure of bovine rhodopsin, however, revealed that the second extracellular loop (E2), which connects TM4 and TMS, folds down into the transmembrane domain and forms part of the ligand-binding surface for retinal. Whether E2 plays a related role in other rhodopsin-like GPCRs is unclear. To address this issue, we have now mutated to cysteine, one at a time, 10 consecutive residues in E2 of D2R. The reaction of five of these mutants with sulfhydryl reagents inhibited antagonist binding, and bound antagonist protected two, I184C and N186C, from reaction. The pattern of accessibility in E2 is consistent with a structure similar to that of bovine rhodopsin, in which the region C-terminal to the conserved disulfide bond is deeper in the binding-site crevice than is the N-terminal part of E2. Thus, E2 likely contributes to the binding site in the D2R and probably in other aminergic GPCRs as well. Knowledge of its detailed positioning and interactions with ligand would benefit GPCR molecular modeling and facilitate the design of novel drugs.