Sodium and Sulfate Ion Transport in Yeast Vacuoles

• Published in: Journal of biochemistry (Tokyo) Vol. 131; no. 2; pp. 261 - 265
• Main Authors: Hirata, Tomoyuki, Wada, Yoh, Futai, Masamitsu
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 01-02-2002
• Subjects: acidic organells; Biological Transport, Active - drug effects; Carrier Proteins - metabolism; Cell Membrane - drug effects; Cell Membrane - physiology; Hydrogen-Ion Concentration; Intracellular Membranes - enzymology; Membrane Potentials - drug effects; Membrane Transport Proteins; Mutation; Proton Pumps - metabolism; Recombinant Proteins - metabolism; Saccharomyces cerevisiae - metabolism; Sodium - metabolism; Sodium-Hydrogen Exchangers - antagonists & inhibitors; Sodium-Hydrogen Exchangers - genetics; Sodium-Hydrogen Exchangers - metabolism; sodium/proton antiport; sulfate transport; Sulfate Transporters; Sulfates - metabolism; V-ATPase; Vacuolar Proton-Translocating ATPases - antagonists & inhibitors; Vacuolar Proton-Translocating ATPases - genetics; Vacuolar Proton-Translocating ATPases - metabolism; Vacuoles - enzymology; Vacuoles - metabolism; yeast vacuole
• ISSN: 0021-924X
• DOI: 10.1093/oxfordjournals.jbchem.a003097

The intra-luminal acidic pH of endomembrane organelles is established by a proton pump, vacuolar H+-ATPase(V-ATPase), in combination with other ion transporters). The proton gradient (ApH) established in yeast vacuolar vesicles decreased and reached the lower value after the addition of alkaline cations including NaAs+. As expected, the uptake of 22Na+was coupled with ApH generated by V-ATPase. Disruption of NHX1 or NHA1, encoding known Na7H+ antiporters, did not result in the loss of 22Na+ uptake or the alkaline cation-dependent ApH in thedecrease. Upon the addition of sulfate ions, the V-ATPase-dependent ApH in the vacuolar vesicles increased, but the membrane potential(AW) decreased. Consistent with this observation, radioactive sulfate was transported into the vesicles with a Km value of 0.07 mM. The transport activity was unaffected upon disruption of the putative genes coding for homologues of plasma membrane sulfate transporters. These results indicate that the vacules exhibit unique Na+/H+antiport and sulfate transport, which regulate the luminal pH and ion homeostasis in yeast.