Vacuolar antiporter that acts in low affinity electroneutral exchange of protons H(+) for cations such as Na(+) or K(+) across membranes (PubMed:14988485). Plays important roles in the transport of Na(+) and K(+) accumulated in the cytoplasm into vacuoles, and is involved in salt stress tolerance (PubMed:14988485). H(+)(out) + Na(+)(in) = H(+)(in) + Na(+)(out) H(+)(out) + K(+)(in) = H(+)(in) + K(+)(out) Induced by NaCl in roots and shoots (PubMed:10395929, PubMed:14988485). Induced by KCl in roots and shoots (PubMed:14988485). Plants overexpressing NHX1 exhibit improved tolerance to salt stress. Belongs to the monovalent cation:proton antiporter 1 (CPA1) transporter (TC 2.A.36) family. Extended N-terminus.