The structure of the vacuolar ATPase in Neurospora crassa

The filamentous fungus Neurospora crassa contains many small vacuoles. Thes e organelles contain high concentrations of polyphosphates and basic amino acids, such as arginine and ornithine. Because of their size and density, t he vacuoles can be separated from other organelles in the cell. The ATP-dri ven proton pump in the vacuolar membrane is a typical V-type ATPase. We exa mined the size and structure of this enzyme using radiation inactivation an d electron microscopy. The vacuolar ATPase is a large and complex enzyme, w hich appears to contain at least thirteen different types of subunits. We h ave characterized the genes that encode eleven of these subunits. In this r eview, we discuss the possible function and structure of these subunits.