Cloning, functional expression and primary characterization of Vibrio parahaemolyticus K+/H+ antiporter genes in Escherichia coli
Cloning, functional expression and primary characterization of Vibrio parahaemolyticus K+/H+ antiporter genes in Escherichia coli
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DOI：
10.1111/j.1365-2958.2005.04966.x
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发表时间：
2006-01-01
影响因子：
3.6
通讯作者：
Nakamura, T
中科院分区：
文献类型：
--
作者：
Radchenko, MV;Waditee, R;Nakamura, T
体内Na+和K+浓度的调节对细菌细胞很重要，在没有Na+排出系统的情况下，细菌细胞不能在外部高Na+存在的情况下生长。同样，当外部K+浓度变得太低而不能支持生长时，细菌需要K+吸收系统。目前，我们对K+的毒性和细菌的外向K+转运系统知之甚少。我们在这里报告了在碱性pH下高浓度的K+是有毒的，细菌需要K+外流和/或排泄系统来避免K+的过度积累。我们已经从副溶血性弧菌中鉴定出第一例细菌K+(特异性)/H+逆向转运蛋白VP-NhaP2。该蛋白是阳离子质子反向转运蛋白-1(CPA1)家族的成员，能够介导K+从细胞中排出，从而在碱性pH条件下耐受高浓度的外部KCl。我们还发现了副溶血性弧菌的两个Na+/H+逆向转运蛋白，Vp-NhaA和Vp-NhaB，它们对K+也表现出新的离子专一性，这意味着它们可能是Na+(K+)/H+交换。此外，在特定条件下，大肠杆菌能够调节K+化学梯度的K+排出，这表明大肠杆菌也有一个未知的K+排出系统(S)。
The regulation of internal Na+ and K+ concentrations is important for bacterial cells, which, in the absence of Na+ extrusion systems, cannot grow in the presence of high external Na+. Likewise, bacteria require K+ uptake systems when the external K+ concentration becomes too low to support growth. At present, we have little knowledge of K+ toxicity and bacterial outward-directed K+ transport systems. We report here that high external concentrations of K+ at alkaline pH are toxic and that bacteria require K+ efflux and/or extrusion systems to avoid excessive K+ accumulation. We have identified the first example of a bacterial K+(specific)/H+ antiporter, Vp-NhaP2, from Vibrio parahaemolyticus. This protein, a member of the cation : proton antiporter-1 (CPA1) family, was able to mediate K+ extrusion from the cell to provide tolerance to high concentrations of external KCl at alkaline pH. We also report the discovery of two V. parahaemolyticus Na+/H+ antiporters, Vp-NhaA and Vp-NhaB, which also exhibit a novel ion specificity toward K+, implying that they work as Na+(K+)/H+ exchangers. Furthermore, under specific conditions, Escherichia coli was able to mediate K+ extrusion against a K+ chemical gradient, indicating that E. coli also possesses an unidentified K+ extrusion system(s).