Stoichiometry of Na+ to H+ in Na+/H+ antiporter

Range at pH=7.4 1.1: at pH=7.8 1.3: at pH=8.4 1.4 unitless
Organism Bacteria Escherichia coli
Reference Taglicht D, Padan E, Schuldiner S. Overproduction and purification of a functional Na+/H+ antiporter coded by nhaA (ant) from Escherichia coli. J Biol Chem. 1991 Jun 15 266(17):11289-94. p.11289 right column top paragraphPubMed ID1645730
Primary Source Pan JW, Macnab RM. Steady-state measurements of Escherichia coli sodium and proton potentials at alkaline pH support the hypothesis of electrogenic antiport. J Biol Chem. 1990 Jun 5 265(16):9247-50.PubMed ID2160968
Comments p.11289 left column bottom paragraph:"In most bacterial cells, the antiporter is the major Na+-extruding mechanism driven by the inwardly directed H+- electrochemical gradient. In contrast to the human protein, which is electroneutral, the bacterial one is electrogenic with an overall stoichiometry of H+ to Na+ above 1 (Schuldiner and Fishkes, 1978 Castle et al., 1986 & primary source), and it is activated by alkaline rather than acid pH (Leblanc et al., 1988). The overall apparent stoichiometry was measured over a wide pH range. It was shown that the stoichiometry changes from 1.1 at pH 7.4 to 1.3 at pH 7.8 and reaches 1.4 at pH 8.4 (primary source Pan & Macnab). Macnab and collaborators suggest the possible existence of two antiporters, one electroneutral and the other electrogenic with a stoichiometry (H+:Na+) of 2, which when functioning together, yield the apparent nonintegral stoichiometry (Castle et al., 1986 & primary source)."
Entered by Uri M
ID 111776