title: Kinetics of pyrophosphate-driven proton uptake by acidocalcisomes of Leptomonas wallacei.
abstract: In this work, we show the kinetics of pyrophosphate-driven H+ uptake by acidocalcisomes in digitonin-permeabilized promastigotes of Leptomonas wallacei. The vacuolar proton pyrophosphatase activity was optimal in the pH range of 7.5-8.0, was inhibited by imidiodiphosphate, and was completely dependent on K+ and PPi. H+ was released with the addition of Ca2+, suggesting the presence of a Ca2+/H+ antiport. In addition, X-ray elemental mapping associated with energy-filtering transmission electron microscopy showed that most of the Ca, Na, Mg, P, K, Fe, and Zn were located in acidocalcisomes. L. wallacei immunolabeled with antibodies against Trypanosoma cruzi pyrophosphatase show intense fluorescence in cytoplasmatic organelles of size and distribution similar to the acidocalcisomes. Altogether, the results show that L. wallacei acidocalcisomes possess a H+-pyrophosphatase with characteristics of type I V-H+-PPase. However, we did not find any evidence, either for the presence of H+-ATPases or for Na+/H+ exchangers in these acidocalcisomes.
authors.affiliation: Instituto de Bioquímica Médica, Programa de Biologia Estrutural, Universidade Federal do Rio de Janeiro, Brazil.
authors.forename: Bernardo Luiz
authors.initials: BL
authors.lastname: Moraes Moreira
authors.forename: Lia Carolina A
authors.initials: LC
authors.lastname: Soares Medeiros
authors.forename: Kildare
authors.initials: K
authors.lastname: Miranda
authors.forename: Wanderley
authors.initials: W
authors.lastname: de Souza
authors.forename: Joachim
authors.initials: J
authors.lastname: Hentschel
authors.forename: Helmut
authors.initials: H
authors.lastname: Plattner
authors.forename: Hector
authors.initials: H
authors.lastname: Barrabin
mesh_terms: D000818:Animals; D003594:Cytoplasmic Granules / Q000378:metabolism* / Q000648:ultrastructure*; D011756:Diphosphates / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D043564:Inorganic Pyrophosphatase / Q000378:metabolism*; D007700:Kinetics; D011522:Protons; D014351:Trypanosomatina / Q000166:cytology* / Q000378:metabolism*
chemical_list: D011756:Diphosphates; D011522:Protons; D043564:Inorganic Pyrophosphatase