The yeast Saccharomyces cerevisiae vacuolar H+-ATPase (V-ATPase) is a multisubunit complex responsible for acidifying organelles. It functions as an ATP dependent proton pump that transports protons across a lipid bilayer. This domain corresponds to the N terminal domain of the H subunit of V-ATPase. The N-terminal domain is required for the activation of the complex whereas the C-terminal domain is required for coupling ATP hydrolysis to proton translocation.