Endosomal/prevacuolar electroneutral Na(+)/H(+) exchanger which mediates intracellular sequestration of Na(+) cations, regulates vacuolar pH and contributes to osmotolerance following sudden exposure to hyperosmotic media. Contributes also to the postdiauxic/stationary phase resistance to osmotic stress and allows for the continued growth of cells until the acquired osmotolerance response can occur. Involved in hygromycin resistance probably through its influence on the electrochemical proton gradient affecting secondarily the entrance of hygromycin. Mediates pH-dependent vesicle trafficking out of the endosome. Contributes to K(+) sequestration and homeostasis. Interacts with CYP6. Present with 521 molecules/cell in log phase SD medium. Belongs to the monovalent cation:proton antiporter 1 (CPA1) transporter (TC 2.A.36) family. Numerous studies suggest that the C-terminal tail of the Na(+)/H(+) exchangers assumes a cytosolic orientation and constitutes a regulatory region. This cytosolic localization is confirmed by phosphorylation analysis (PubMed:15665377 and PubMed:18407956). However, residues Asn-515, Asn-550 and Asn-563 have been shown to be glycosylated and localized at the lumenal side (PubMed:11036065). These contradictory results suggest an unusual topology of the C-terminal tail which may contain membrane spans formed by beta-sheets or even may switch from one side to the other of the membrane.