The vacuolar-type H(+) -ATPase acidifies intracellular compartments and is essential for many processes, including cotransport, guard cell movement, development, and tolerance to environmental stress. There are at least 26 subunits of the vacuolar-type H(+) -ATPase in the Arabidopsis thaliana. The pump consists of subunits A through H of the peripheral V(1) complex, and subunits a, c, c" and d of the V(o) membrane sector.
