Structure and Mechanism of a Virtual Proton Pump

描述(由申请人提供)：本提案的目的是确定ADIC的结构，ADIC是一类广泛存在且鲜为人知的膜运输蛋白-APC超家族的成员。APC蛋白在生物世界中几乎无处不在，用于将氨基酸、多胺和各种有机阳离子转移到细胞膜上，用于多种生理目的。虽然这是一个庞大的分子超家族，但目前还没有任何APC蛋白的高分辨率结构，而且我们目前对其底物转运的基本机制的了解也很浅。细菌的APC蛋白ADIC将精氨酸转移到许多肠道细菌中，是这些微生物在暴露于胃的酸性环境中生存的“极端耐酸”反应中的关键角色。这种特殊的APC蛋白可以过度表达、纯化、在人造膜中进行功能重组，最重要的是，结晶。该项目旨在通过X射线结晶学确定ADIC的结构，并利用这一结构信息来了解该蛋白质如何专门识别其有机阳离子底物以及它如何在生物膜上移动阈值。

DESCRIPTION (provided by applicant): The aim of this proposal is to determine the structure of AdiC, a member of a widespread and little-understood class of membrane transport proteins - the APC superfamily. APC proteins, nearly ubiquitous in the biological world, are used to move amino acids, polyamines, and a variey of organic cations across cell membranes for a multitude of physiological purposes. Although this is a huge molecular superfamily, no high-resolution structures are known for any APC proteins, and our understanding of their fundamental mechanisms of substrate transport is currently shallow. The bacterial APC protein AdiC, which moves arginine into many enteric bacteria, is a key player in the "extreme acid resistance" response that these organisms use to survive exposure to the acid environment of the stomach. This particular APC protein may be overexpressed, purified, functionally reconstituted in artificial membranes, and, most importantly, crystallized. The project aims to determine the structure of AdiC by x-ray crystallography, and to use this structural information to understand how this protein specifically recognizes its organocationic substrates and how it moves threse across the biological membrane.