Bacterial pathogens are a major cause of foodborne diseases and food poisoning. To cope with the acid conditions encountered in different environments such as in fermented food or in the gastric compartment, neutralophilic bacteria have developed several adaptive mechanisms. One of those mechanisms, the amino acid dependent system, consumes intracellular protons in biochemical reactions. It involves an antiporter that facilitates the exchange of external substrate amino acid for internal product and a cytoplasmic decarboxylase that catalyzes a proton-consuming decarboxylation of the substrate. So far, four acid resistance antiporters have been discovered, namely the glutamate-γ-aminobutyric acid antiporter GadC, the arginine-agmatine antiporter AdiC, the lysine-cadaverine antiporter CadB, and the ornithine-putrescine antiporter PotE. The 3D structures of AdiC and GadC, reveal an inverted-repeat fold of two times 5 transmembrane helices, typical of the amino acid-polyamine-organocation (APC) superfamily of transporters. This review summarizes our current knowledge on the transport mechanism, the pH regulation and the selectivity of these four acid resistance antiporters. It also highlights that AdiC is a paradigm for eukaryotic amino acid transporters of the APC superfamily as structural models of several of these transporters built using AdiC structures were exploited to unveil their mechanisms of amino acid recognition and translocation.

中文翻译：

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抗酸反转运蛋白的功能和调节。

细菌病原体是食源性疾病和食物中毒的主要原因。为了应付在诸如发酵食品或胃隔室等不同环境中遇到的酸性条件，嗜中性细菌已发展出几种适应性机制。这些机制之一是氨基酸依赖性系统，它在生化反应中消耗细胞内质子。它涉及促进外部底物氨基酸交换为内部产物的反转运蛋白和催化底物的质子消耗脱羧的胞质脱羧酶。迄今为止，已经发现了四种耐酸逆转运蛋白，即谷氨酸-γ-氨基丁酸逆转运蛋白GadC，精氨酸-胍丁胺逆转运蛋白AdiC，赖氨酸-尸胺逆转运蛋白CadB和鸟氨酸-鸟氨酸逆转运蛋白PotE。AdiC和GadC的3D结构揭示了5倍跨膜螺旋的反向重复折叠，这是转运蛋白的氨基酸-多胺-有机结合（APC）超家族的典型特征。这篇综述总结了我们目前对这四种耐酸反转运蛋白的转运机理，pH调节和选择性的认识。它还强调了AdiC是APC超家族真核氨基酸转运蛋白的范例，因为利用AdiC结构构建的这些转运蛋白中的几种转运蛋白的结构模型被用来揭示其氨基酸识别和转运的机制。这篇综述总结了我们目前对这四种耐酸性反转运蛋白的转运机理，pH调节和选择性的认识。它还强调了AdiC是APC超家族真核氨基酸转运蛋白的范例，因为利用AdiC结构构建的这些转运蛋白中的几种转运蛋白的结构模型被用来揭示其氨基酸识别和转运的机制。这篇综述总结了我们目前对这四种耐酸性反转运蛋白的转运机理，pH调节和选择性的认识。它还强调了AdiC是APC超家族真核氨基酸转运蛋白的范例，因为利用AdiC结构构建的这些转运蛋白中的几种转运蛋白的结构模型被用来揭示其氨基酸识别和转运的机制。