DOPAMINE TRANSPORTER-- STRUCTURE AND FUNCTION RELATIONSHIPS

多巴胺转运体/可卡因受体(DAT)是 可卡因起到奖励/强化的作用。DAT的最新克隆 CDNA允许通过以下方式寻找DAT的结构/功能关系 选择性残基的突变及其对可卡因类似物的影响 识别和多巴胺的运输。突变优先影响 其中一个过程为这种可能性提供了新的直接证据 抗可卡因药物会对其中一种产生不同的影响 进程，而不是其他进程。因为定义氨基酸的工作 对儿茶酚胺受体识别儿茶酚胺很重要，以及 数据表明，可卡因的极地区域对 转运体对该分子的识别作用，跨膜中极性残基 基因片段发生了突变。了解半胱氨酸残留物将有助于 了解分子结构。 天冬氨酸79的替代显著减少了多巴胺和 MPP+和突变体对CFT的亲和力不影响B(Max)。 第7疏水区丝氨酸的替换减少了多巴胺 和MPP+摄取，同时保留CFT结合。在第8天改变丝氨酸 疏水区没有影响。这些结果表明， 天冬氨酸和丝氨酸残基位于假定的跨膜区 对于DAT功能至关重要，并提供了第一个标识 残留对可卡因结合和多巴胺具有不同的重要性 领悟。阐明可能的胞外区的结构 也很重要。取代DAT秒中的半胱氨酸 选择性且有趣的疏水推定的胞外结构域 降低突变转运蛋白的功能，反之，替代 对于其他两种胱氨酸中的任何一种都没有显著影响。功能 因此，转运体二级结构对转运体很重要 功能。

The dopamine transporter/cocaine receptor (DAT) is the site at which cocaine exerts rewarding/reinforcing effects. Recent cloning of the DAT cDNA allows structure/function relationships of the DAT to be sought by mutating selected residues and examining influences on cocaine analog recognition and dopamine transport. Mutations preferentially affecting one of these processes provide novel direct evidence for the possibility that anticocaine medications could differentially impact one of these processes but not the other. Because of work defining the amino acids important for catecholamine recognition by catecholamine receptors, and data suggesting that polar regions of cocaine are important for transporter recognition of this molecule, polar residues in transmembrane segments were mutated. Knowledge about cysteine residues would help to understand the molecule's structure. Substitution of aspartate 79 dramatically reduced uptake of dopamine and MPP+ and the mutants' affinity for CFT without affecting B(max). Replacement of the serines in the 7th hydrophobic region reduced dopamine and MPP+ uptake, while sparing CFT binding. Changing serines in the 8th hydrophobic region has no effects. These results demonstrate that aspartate and serine residues lying within putative transmembrane regions are crucial for DAT function, and provide the first identification of residues differentially important for cocaine binding and for dopamine uptake. Elucidating the structures of the putative extracellular domains is also important. Substitution for the cysteines in the DAT second hydrophobic putative extracellular domain selectively and interestingly decreases the function of mutant transporters, conversely, substitution for either of two other cystines had no significant influence. Features of transporter secondary structure are thus important for transporter function.