In plants and fungi, the transport of solutes across the plasma membrane (pm) is driven by a proton pump (H⁺-ATPase) that produces an electric potential and a pH gradient. We expressed AHA2, a member of the Arabidopsis thaliana pm H⁺-ATPase gene family, in yeast cells in which transcription of the endogenous pm H⁺ATPase gene (pmal) had been turned off. AHA2 was expressed mainly in intracellular membranes and only supported very slow growth of transformed yeast cells. Removal of the last 92 C-terminal amino acids from the plant H⁺-ATPase produced an enzyme with 2-3-fold higher specific ATPase activity than the wild-type plant enzyme. Surprisingly, the truncated H⁺-ATPase was now targetted to the yeast pm and fully supported normal yeast growth.