K(+)/H(+) antiporter that extrudes potassium in exchange for external protons and maintains the internal concentration of potassium under toxic levels. H(+)(out) + K(+)(in) = H(+)(in) + K(+)(out) Belongs to the monovalent cation:proton antiporter 1 (CPA1) transporter (TC 2.A.36) family. NhaP2 subfamily. Truncated N-terminus. Truncated N-terminus.