Pinner E, Carmel O, Bercovier H, Sela S, Padan E, Schuldiner S
Department of Molecular and Microbial Ecology, Institute of Life Sciences, Hebrew University of Jerusalem, Israel.
Arch Microbiol. 1992;157(4):323-8. doi: 10.1007/BF00248676.
Na+/H+ antiporter activity is wide-spread and plays essential physiological roles. We found that several Enterobacteriaceae share conserved sequences with nhaA, the gene coding for an E. coli antiporter. A delta nhaA strain, which is sensitive to Na+ and Li+, was used to clone by complementation a DNA fragment from Salmonella enteritidis which confers resistance to the ions. The cloned fragment increased Na+/H+ antiport activity in membranes isolated from strains carrying the respective hybrid plasmid. DNA sequence analysis of the insert revealed two open reading frames. Both encode putative polypeptides which are closely homologous to the nhaA and nhaR gene products from Escherichia coli. The antiporter activity displays properties very similar to that of the E. coli NhaA, namely, it is activated by alkaline pH and recognizes Li+ with high affinity.
钠氢反向转运体活性广泛存在并发挥着重要的生理作用。我们发现几种肠杆菌科细菌与nhaA具有保守序列，nhaA是编码大肠杆菌一种反向转运体的基因。利用对Na⁺和Li⁺敏感的ΔnhaA菌株，通过互补克隆来自肠炎沙门氏菌的一段赋予离子抗性的DNA片段。克隆片段增加了携带相应杂交质粒菌株分离膜中的钠氢反向转运活性。对插入片段的DNA序列分析揭示了两个开放阅读框。两者都编码与大肠杆菌的nhaA和nhaR基因产物密切同源的假定多肽。该反向转运体活性表现出与大肠杆菌NhaA非常相似的特性，即它在碱性pH下被激活并对Li⁺具有高亲和力。
