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  • Title: Overproduction and purification of a functional Na+/H+ antiporter coded by nhaA (ant) from Escherichia coli.
    Author: Taglicht D, Padan E, Schuldiner S.
    Journal: J Biol Chem; 1991 Jun 15; 266(17):11289-94. PubMed ID: 1645730.
    Abstract:
    A Na+/H+ antiporter coded by the nhaA (ant) gene of Escherichia coli has been overproduced and purified. The amino-terminal sequence of the protein has been determined and shown to correlate with initiation at a GUG codon, 75 bases upstream from the previously suggested AUG initiation codon. The purified protein, when reconstituted into proteoliposomes, has Na+/H+ antiport activity. It can mediate sodium uptake when a transmembrane pH gradient is applied. Downhill sodium efflux is shown to be highly dependent on pH and is accelerated by a transmembrane pH gradient. An imposed membrane potential negative inside accelerates Na+ efflux at all pH values tested. These findings suggest that the antiporter is electrogenic both at acid and alkaline pH. The activation at alkaline pH values (2000-fold increase) is consistent with the proposed role of the antiporter in regulation of internal pH at the alkaline pH range.
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