D'Souza U M, Strange P G
Research School of Biosciences, The University, Canterbury, U.K.
Biochemistry. 1995 Oct 17;34(41):13635-41. doi: 10.1021/bi00041a044.
The binding of a range of ligands to D2 dopamine receptors in bovine caudate nucleus and recombinant CHO cells expressing the receptor has been determined at different pH values between 4.5 and 8.5. The maximum number of D2 dopamine receptor binding sites in each tissue was not affected by the change in pH, but the affinity of ligands for binding to the receptors was decreased as the pH was decreased. For classical dopamine antagonists, e.g. spiperone and haloperidol, the data on pH dependence of the dissociation constant for receptor binding indicated that the protonation of a single ionizing group on the receptor (pKa approximately 6) influenced the binding process. For antagonists of the substituted benzamide class, the data indicated that the protonation of two ionizing groups (pKa between 6 and 7) influenced the ligand binding process. These ionizing residues may correspond to Asp 114 for the classical antagonists and Asp 114 and Asp 80 for the substituted benzamide antagonists. Further evidence for the participation of carboxyl residues in the ligand binding process was obtained from the inhibition by N,N'-dicyclohexylcarbodiimide of the binding of [3H]spiperone and [3H]YM 09151-2 to D2 receptors in the recombinant CHO cells.
已在4.5至8.5的不同pH值下测定了一系列配体与牛尾状核中的D2多巴胺受体以及表达该受体的重组CHO细胞的结合情况。每个组织中D2多巴胺受体结合位点的最大数量不受pH变化的影响，但随着pH值降低，配体与受体结合的亲和力会下降。对于经典的多巴胺拮抗剂，如螺哌隆和氟哌啶醇，受体结合解离常数的pH依赖性数据表明，受体上单个电离基团的质子化（pKa约为6）影响了结合过程。对于取代苯甲酰胺类拮抗剂，数据表明两个电离基团的质子化（pKa在6至7之间）影响了配体结合过程。这些电离残基可能对应于经典拮抗剂的天冬氨酸114以及取代苯甲酰胺拮抗剂的天冬氨酸114和天冬氨酸80。通过N，N'-二环己基碳二亚胺对重组CHO细胞中[3H]螺哌隆和[3H]YM 09151-2与D2受体结合的抑制作用，获得了羧基残基参与配体结合过程的进一步证据。
