Endomembrane-localized H(+)-dependent K(+) and Na(+) transporter. May have a function associated with the pollen vacuole during tube elongation and polarized top growth. Expressed in roots, leaves, stems and flowers. Up-regulated by exogenous Na(+), K(+) and Mn(2+). No visible phenotype. Belongs to the Ca(2+):cation antiporter (CaCA) (TC 2.A.19) family. Cation/calcium exchanger (CCX) subfamily.