High-affinity potassium transporter that plays a role in K(+) acquisition. May operate as a K(+)/H(+) symporter. Preferentially expressed in pollen before and after germination. Detected in pollen grains within anthers of the flower buds or in pollen on fully open flowers and on the stigma, and in pollen tubes growing in the style. Weakly expressed in roots. Transiently induced by K(+) depletion. No visible phenotype under standard growth conditions, but growth inhibition and leaf chlorosis and bleaching under low K(+) conditions. K(+) uptake enhanced by a proton electrochemical gradient (acidic outside). Not affected by specific inhibitors of voltage-gated K(+) channels. Belongs to the monovalent cation:proton antiporter 2 (CPA2) transporter (TC 2.A.37) family. CHX (TC 2.A.37.4) subfamily.