Collapse of ATP-Induced pH Gradient by Sodium Ions in Microsomal Membrane Vesicles Prepared from Atriplex gmelini Leaves: Possibility of Na+/H+ Antiport

AUTOR(ES)

Matoh, Tōru

RESUMO

Sealed microsomal membrane vesicles were prepared from leaves of a 250 millimolar NaCl-grown halophyte (Atriplex gmelini C. A. Mey). The vesicles exhibited ATP-dependent proton-transporting activity which was inhibited 60% by NO3− (50 millimolar) but not by vanadate (100 micromolar) and 23% by oligomycin (10 micrograms per milliliter), suggesting that tonoplast-derived vesicles were the major constituents of the preparation. The pH gradient established by the vesicles by ATP in the presence of oligomycin collapsed upon the addition of Na+ salts. The vesicles took up Na+ ions in the presence of ATP and this activity was canceled by gramicidin. These results suggest that Na+ ions were taken up by the vesicles via a Na+-specific uptake system, possibly a Na+/H+ antiport.

Documentos Relacionados

• Kinetic properties of electrogenic Na+/H+ antiport in membrane vesicles from an alkalophilic Bacillus sp.
• Evidence for a Na+/H+ Antiporter in Membrane Vesicles Isolated from Roots of the Halophyte Atriplex nummularia1
• NaCl Induces a Na+/H+ Antiport in Tonoplast Vesicles from Barley Roots 1
• Focal localization of the NHE-1 isoform of the Na+/H+ antiport: assessment of effects on intracellular pH.
• Characterization of the activation of Na+/H+ exchange in lymphocytes by phorbol esters: change in cytoplasmic pH dependence of the antiport.