A plant-like vacuolar H+-pyrophosphatase in Plasmodium falciparum

Inorganic pyrophosphate promoted the acidification of a subcellular compart ment in cell homogenates of Plasmodium faliciparum trophozoites, The proton gradient driven by pyrophosphate was collapsed by addition of NH4Cl or the K+/H+ exchanger nigericin and eliminated by the pyrophosphate analog amino methylenediphosphonate. Pyrophosphatase activity was dependent upon K+, and partially inhibited by Na+, The presence of a plant-like vacuolar H+-trans locating pyrophosphatase (V-H+-PPase) was confirmed using antibodies raised against conserved peptide sequences of the enzyme, which cross reacted wit h a protein band of 76.5 kDa, Immunofluorescence microscopy using these ant ibodies showed a general fluorescence over the whole parasites and intracel lular bright spots suggesting a vesicular and plasma membrane localization, Together, these results indicate the presence in P. falciparum of a V-H+-P Pase of similar characteristics to those of the enzyme from plants. (C) 199 9 Federation of European Biochemical Societies.