Characteristics of ion tranport systems in Vibrio parahaemolyticus and Staphylococcus aureus

副溶血性弧菌和金黄色葡萄球菌是日本食物中毒的两个主要原因。金黄色葡萄球菌也是医院感染的主要原因。前者的生长需要Na^+，后者是一种耐Na^+的微生物。基于这些特性，我们研究了这些微生物的离子转运系统，特别是Na^+转运系统。我们对这类转运系统进行了生物化学和分子生物学的表征，研究了它们的嗜盐性和耐盐性与Na^+转运的关系，并对副溶血性弧菌的Na^+/H^+反向转运蛋白进行了鉴定和基因克隆。此后，我们对该基因进行了测序，并揭示了反向转运蛋白的一级结构。我们发现了大肠杆菌Na^+/H^+反向转运蛋白和NhaB Na^+/H^+反向转运蛋白之间的序列相似性。因此，我们将副溶血弧菌的反向转运蛋白命名为NhaB，并鉴定了Na^+/H^+反向转运蛋白的几个功能性氨基酸残基。我们还发现了第三种Na^+/H^+逆向转运蛋白NhaD，并对其进行了鉴定，克隆了该基因并进行了序列测定。我们发现它是一种新型的Na^+/H^+逆向转运蛋白。Na^+/H^+反向转运蛋白在植物的嗜盐性和耐盐性中起着重要的作用。Na^+/葡萄糖同向转运体（SglS）也被表征。我们克隆了SglS的结构基因并进行了序列测定，发现SglS与人SGLT、Na^+/葡萄糖同向转运体的序列相似，建立了一种制备金黄色葡萄球菌翻转膜囊泡的方法。我们发现该微生物中存在Na^+/H^+逆向转运蛋白。我们对其进行了鉴定，克隆了结构基因并进行了测序。这种Na^+/H^+逆向转运蛋白是一种新型的逆向转运蛋白。我们发现，这种反向转运蛋白参与halotorelance和细胞内pH调节。

Vabrio parahaemolyticus and Staphylococcus aureus are two major causes of food poisoning in Japan. S.aureus is also a major cause of infection in hospitals. The former requires Na^+ for its growth, and the latter is a Na^+-torelant microorganism. Base on these characteristics, we investigated ion transport systems, especially Na^+ transport systems, in these microorganisms. We biochemically and molecular biologically characterized such transport systems, and investigated relationship between halophilicity or halotorelance of these bacteria and Na^+ transport.We characterized the Na^+/H^+ antiporter in V.parahaemolyticus and cloned gene for the antiporter. We thereafter sequenced the gene and revealed the primary structure of the antiporter. We found sequence similarity between the Na^+/H^+ antiporter and the NhaB Na^+/H^+ antiporter of Escherichia coli. Thus, we designated the antiporter of V.parahaemolyticus as NhaB.We identified several functional amino acid residues of the Na^+/H^+ antiporters. We also found the third Na^+/H^+ antiporter NhaD and characterized it. The gene was cloned and sequenced. We found that it was a new type of Na^+/H^+ antiporter. It became claer that the Na^+/H^+ antiporters are very important for halophilicity and halotorelance. The Na^+/glucose symporter (SglS) was also characterized. We cloned the structural gene and sequenced it. We found sequence similarity between the SglS and human SGLT,Na^+/glucose symporter.We developed a method for the preparation of everted membrane vesicles of S.aureus. We found that Na^+/H^+ antiporter is present in this microorganism. We characterized it, cloned the structural genes and sequenced them. This Na^+/H^+ antiporter was revelaed to be a novel type of antiporter. We found that this antiporter is involved in halotorelance and intracellular pH regulation.