A VACUOLAR ATPASE AND PYROPHOSPHATASE IN ACETABULARIA-ACETABULUM

Vacuole-rich fractions were isolated from Acetabularia acetabulum by Ficoll step gradient centrifugation. The tonoplast-rich vesicles showed ATP-dependent and pyrophosphate-dependent H+-transport activities. ATP-dependent H+-transport and ATPase activity were both inhibited by the addition of a specific inhibitor of vacuolar ATPase, bafilomycin B1. A 66 kDa polypeptide present in the preparation cross-reacted with the anti-IgG fractions against the alpha and beta subunits of Halobacterium halobium ATPase and with the antibody against the A subunit (68 kDa subunit) of mung bean vacuolar ATPase. A 56 kDa polypeptide present in the vacuole preparation showed cross-reactivity with the antibody against the B subunit (57 kDa) of mung bean vacuolar ATPase but not with the anti-beta subunit of H. halobium ATPase. A 73 kDa polypeptide cross-reacted with the antibody against inorganic pyrophosphatase of mung bean vacuoles. These results suggest that vacuolar membrane of A. acetabulum equipped energy transducing systems similar to those found in other plant vacuoles.