Essential aspartic acid residues, Asp‐133, Asp‐163 and Asp‐164, in the transmembrane helices of a Na+/H+ antiporter (NhaA) from Escherichia coli

FEBS Letters

Kanazawa, Hiroshi¹  Noumi, Takato¹  Inoue, Hiroki¹  Tsuchiya, Tomofusa² 

[1] Department of Biotechnology, Faculty of Engineering, Okayama University, 3-1-1 Tsushima-naka, Okayama 700, Japan;Department of Microbiology, Faculty of Pharmaceutical Sciences, Okayama University, Okayama 700, Japan

关键词: NhaA;    Na+/H+ antiporter;    Li+ ion;    pH sensor;    Transporter;   

DOI  :  10.1016/0014-5793(95)00331-3

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

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 N⁺/H⁺ and L⁺/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.

【 授权许可】

Unknown