The Neurotransmitter: Sodium Symporter Permeation Pathway

生物胺转运体在其特定神经递质的作用和循环中发挥重要作用 底物。它们已被确定为许多药理制剂的靶标，这些药剂可以影响 大脑功能。例如，滥用毒品可卡因和苯丙胺的有益性质是 主要由于其抑制多巴胺转运体(DAT)；丙咪嗪的抗抑郁作用被发挥出来 5-羟色胺转运体(SERT)。这些转运蛋白属于神经递质：钠转运蛋白 (NSS)家族，具有大量的原核同源基因。一种原核亮氨酸转运蛋白(Leut) 结构已经在高分辨率下得到解决，衬底亮氨酸被束缚在一个封闭的腔中。然而， 底物专一性的决定因素，了解底物专一性对于合理的药物设计很重要， 可能不仅位于Leut结构揭示的结合部位缝隙内，而且还沿渗透 路径。本提案的长期目标是阐明经济结构的动态变化 NSS家族蛋白在易位周期中的渗透途径及竞争评价 传输模型，例如，交替存取方案和我们的双衬底模型。具体地说，使用 原核生物NSS-蛋白质作为模型系统，这将通过一个完整的、比较的过程来实现 分子建模模拟和实验调查/验证之间的迭代。有了这个 多学科方案我们将探索保守的残基位置和潜在的辅助空洞 排列渗透途径，并在不同构象状态下动态重组。普通的， 并将比较渗透途径的不同特征，包括钠离子的作用 在原核和真核NSS-蛋白中。所获得的知识应该有助于 生物胺转运体的转位循环，将有助于我们理解 底物特性的基础。

Biogenic amine transporters play important roles in the action and recycling of their specific neurotransmitter substrates. They have been well established as the targets for many pharmacological agents that affect brain function. For examples, the rewarding properties ofthe abused drugs, cocaine and amphetamine, are due mainly to its inhibition of dopamine transporter (DAT); the antidepressant effect of imipramine is exerted on serotonin transporter (SERT). These transporters belong to the Neurotransmitter:Sodium Symporter (NSS) family, which has a large number of prokaryotic homologs. A prokaryotic leucine transporter (LeuT) structure has been solved in high resolution, with the substrate Leu bound in an enclosed cavity. However, the determinants of substrate specificity, an understanding of which is important for rational drug design, may lie not only within the binding site crevice revealed by the LeuT structure, but also along the permeation pathway. The long term goal of the present proposal is to elucidate dynamic structural changes of the permeation pathway of NSS family proteins during the translocation cycle and to evaluate competing transport models, e. g., the alternating-access scheme and our two-substrate model. Specifically, using prokaryotic NSS-proteins as model systems, this will be achieved by an integrated, comparative process of iteration between molecular modeling simulations and experimental investigations/validations. With this multidisciplinary protocol we will explore the conserved residue positions and potential auxiliary cavities that line the permeation pathway and reorganize dynamically in different conformational states. The common, and the different features of the permeation pathways, including the roles of sodium ions, will be compared among prokaryotic and eukaryotic NSS-proteins. The knowledge acquired should shed light on the translocation cycles of biogenic amine transporters and will contribute to our understanding of the structural bases of substrate specificities.