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 transportsprotons across a lipid bilayer. This domain corresponds to theN terminal domain of the H subunit of V-ATPase. The N-terminaldomain is required for the activation of the complex whereas theC-terminal domain is required for coupling ATP hydrolysis toproton translocation [3].