Electroneutral K(+)/H(+) antiporter modulating monovalent cation and pH homeostasis in plastids (PubMed:22551943, PubMed:24278440). Transports K(+) and Cs(+) preferentially relative to Na(+) or Li(+) (PubMed:22551943). May function in osmotic adjustment (PubMed:24278440). A number of isoforms are produced. According to EST sequences. Detected in leaves, stems and flowers (PubMed:22551943). Expressed in shoots and roots (PubMed:24278440). Up-regulated by osmotic stress and down-regulated by high K(+). No visible phenotype. Kea1 and kea2 double mutants display strong growth retardation along with pale green leaves. Kea1, kea2 and kea3 triple mutants are extremely stunted in size with entirely pale leaves and died before steeing seeds. The full-length protein being inactive in a heterologous system, the N-terminal region (58-556) seems to have a regulatory or auto-inhibitory function. Belongs to the monovalent cation:proton antiporter 2 (CPA2) transporter (TC 2.A.37) family. KEA (TC 2.A.37.1) subfamily. Was originally thought to correspond to two different genes At4g00630 and At4g00640. Was originally thought to correspond to two different genes At4g00630 and At4g00640. Sequencing errors. Was originally thought to correspond to two different genes At4g00630 and At4g00640. Was originally thought to correspond to two different genes At4g00630 and At4g00640.