ESSENTIAL ASPARTIC-ACID RESIDUES, ASP-133, ASP-163 AND ASP-164, IN THE TRANSMEMBRANE HELICES OF A NA+/H+ ANTIPORTER (NHAA) FROM ESCHERICHIA-COLI
ESSENTIAL ASPARTIC-ACID RESIDUES, ASP-133, ASP-163 AND ASP-164, IN THE TRANSMEMBRANE HELICES OF A NA+/H+ ANTIPORTER (NHAA) FROM ESCHERICHIA-COLI
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DOI：
10.1016/0014-5793(95)00331-3
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发表时间：
1995-04-24
期刊：
影响因子：
3.5
通讯作者：
KANAZAWA, H
中科院分区：
文献类型：
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作者：
INOUE, H;NOUMI, T;KANAZAWA, H
许多阳离子偶联转运蛋白的跨膜螺旋上的负电荷残基的重要性已被广泛证明，在大肠杆菌Na+/H+逆向转运蛋白nhaA的跨膜螺旋中有四个Asp残基，我们在编码nhaA的质粒中用Asn替换这些残基，并在一个同时缺失nhaA和nhaB的E，Coli突变株中表达这些结构，Asp-65或Asp-282(在膜外区)的替换对宿主突变株在高盐或高LiCl条件下的生长没有影响，这两个突变株具有正常的Na+/H+和Li+/H+反转运体活性，相反，Asp-133的替换Asp-163或Asp-164不利于宿主突变体的存活，并削弱了Na+/H+和Li+/H+逆向转运蛋白的活性。这三个Asp残基在不同物种的nhaA同源物中保守，位于假定的第三和第四跨膜螺旋上，在阳离子结合和运输中发挥着重要作用。
The importance of negatively charged residues in transmembrane helices of many cation-coupled transporters has been widely demonstrated, Four Asp residues were located in the putative transmembrane helices of the Escherichia coli Na+/H+ antiporter, NhaA, We replaced each of these Asp residues by Asn in plasmid encoded nhaA and expressed these constructs in an E, coli mutant defective in both nhaA and nhaB, Substitution of Asp-65 or Asp-282 (in the extramembrane region) had no effect on supporting the host mutant growth in the high NaCl- or LiCl-containing medium, and these two mutants had normal Na+/H+ and Li+/H+ antiporter activities, In contrast, substitution of Asp-133, Asp-163 or Asp-164 was detrimental to survival of the host mutant and impaired both Na+/H+ and Li+/H+ antiporter activities, These three Asp residues, conserved in the nhaA homologs from different species and which are located closely in the 3rd and 4th putative transmembrane helices, appear to play important roles in cation binding and transport.