Purified brush-border membrane vesicles (BBMV) of starfish {Pycnopodia helianthoides) pyloric caecal epithelium were prepared by a magnesium precipitation technique in order to compare the properties of N a + / H + exchange in this invertebrate tissue with those of an apparently unique recently described crustacean electrogenic antiporter. In starfish BBMV ^Na uptake was markedly enhanced by an...

Cytosol 5052 Highlights  The plant Na + /H + antiporter SOS1 is critical for salt tolerance.  SOS1 is a homodimer folded into a transmembrane and a cytosolic domain.  The regulatory mechanism is based on the concerted rearrangement of these domains  The SOS1 structure provides a model valuable for biotechnological applications. Summary The Arabidopsis thaliana Na + /H + antiporter SOS1 is e...

Monovalent cation proton antiporter-3 (Mrp) family antiporters are widely distributed and physiologically important in prokaryotes. Unlike other antiporters, they require six or seven hydrophobic gene products for full activity. Standard fluorescence-based assays of Mrp antiport in membrane vesicles from Escherichia coli transformants have not yielded strong enough signals for characterization ...

Environmental DNA libraries prepared from three different soils were screened for genes conferring Na(+)(Li(+))/H(+) antiporter activity on the antiporter-deficient Escherichia coli strain KNabc. The presence of those genes was verified on selective LK agar containing 7.5 mM LiCl. Two positive E. coli clones were obtained during the initial screening of 1,480,000 recombinant E. coli strains. Bo...

Sodium/proton exchangers (NHX) are key players in plant responses to salinity and have a central role in establishing ion homeostasis. NHXs can be localized in tonoplast or plasma membranes, where they exchange sodium ions for protons, resulting in the removal of ions from the cytosol into vacuole or extracellular spaces. In the present study, the expression pattern of the gene encoding Na+/H+ ...

We studied the ATP dependence of NHE-1, the ubiquitous isoform of the Na+/H+ antiporter, using the whole-cell configuration of the patch-clamp technique to apply nucleotides intracellularly while measuring cytosolic pH (pHi) by microfluorimetry. Na+/H+ exchange activity was measured as the Na(+)-driven pHi recovery from an acid load, which was imposed via the patch pipette. In Chinese hamster o...

Environmental stress factors such as salt, drought and heat are known to affect plant productivity. However, high salinity is spreading throughout the world, currently affecting more than 45 millionha. One of the mechanisms that allow plants to withstand salt stress consists on vacuolar sequestration of Na(+), through a Na(+)/H(+) antiporter. We isolated a new vacuolar Na(+)/H(+) antiporter fro...

We report here that intracellular pH (pH(i)) in cleavage-stage human embryos (2-8-cell) is regulated by at least two mechanisms: the HCO(3)(-)/Cl(-) exchanger (relieves alkalosis) and the Na(+)/H(+) antiporter (relieves acidosis). The mean pH(i) of cleavage-stage embryos was 7.12 +/- 0.008 (n = 199) with little variation between different stages. Embryos demonstrated robust recovery from alkalo...

Thermococcus onnurineus NA1 is known to grow by the anaerobic oxidation of formate to CO2 and H2, a reaction that operates near thermodynamic equilibrium. Here we demonstrate that this reaction is coupled to ATP synthesis by a transmembrane ion current. Formate oxidation leads to H(+) translocation across the cytoplasmic membrane that then drives Na(+) translocation. The ion-translocating elect...

The effect of replacement of negatively charged amino acid residues on the function of Na+ transport proteins of the salt-tolerant yeast Zygosaccharomyces rouxii was examined by heterologous expression of mutant proteins in a strain of Saccharomyces cerevisiae, RH16.6, that lacks native Na+-ATPase activity due to null mutations of ENA1, ENA2, ENA3, and ENA4. Mutants of Na+/H+ antiporter gene (Z...