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Vacuolar type H+ pumping pyrophosphatases of parasitic protozoa
Journal article   Peer reviewed

Vacuolar type H+ pumping pyrophosphatases of parasitic protozoa

Michael T McIntosh, Akhil B Vaidya and Ashok B Vaidya
International journal for parasitology, v 32(1), pp 1-14
Jan 2002
PMID: 11796117

Abstract

Amino Acid Sequence Animals Cell Membrane - enzymology Cell Membrane - genetics Leishmania donovani - enzymology Malaria - drug therapy Molecular Sequence Data Plasmodium - enzymology Plasmodium - genetics Protein Conformation Proton Pumps - chemistry Proton Pumps - genetics Proton Pumps - physiology Pyrophosphatases - chemistry Pyrophosphatases - genetics Pyrophosphatases - physiology Sequence Homology, Amino Acid Toxoplasma - enzymology Trypanosoma - enzymology Vacuoles - enzymology
Trans-membrane proton pumping is responsible for a myriad of physiological processes including the generation of proton motive force that drives bioenergetics. Among the various proton pumping enzymes, vacuolar pyrophosphatases (V-PPases) form a distinct class of proton pumps, which are characterised by their ability to translocate protons across a membrane by using the potential energy released by hydrolysis of the phosphoanhydride bond of inorganic pyrophosphate. Until recently, V-PPases were known to be the purview of only plant vacuoles and plasma membranes of phototrophic bacteria. Recent discoveries of V-PPases in kinetoplastid and apicomplexan parasites, however, have expanded our view of the evolutionary reach of these enzymes. The lack of V-PPases in the vertebrate hosts of these parasites makes them potentially excellent targets for developing broad-spectrum antiparasitic agents. This review surveys the current understanding of V-PPases in parasitic protozoa with an emphasis on malaria parasites. Topological predictions suggest remarkable similarity of the parasite enzymes to their plant homologues with 15-16 membrane spanning domains and conserved sequences shown to constitute critical catalytic residues. Remarkably, malaria parasites have been shown to possess two V-PPase genes, one is an apparent orthologue of the canonical plant enzyme, whereas the other is a more distantly related paralogue with homology to a recently identified new class of K+-insensitive plant V-PPases. V-PPases appear to localise both to the plasma membrane and cytoplasmic organelles believed to be acidocalcisomes or polyphosphate bodies. Gene transfer experiments suggest that one of the malarial V-PPases is predominantly localised to the surface of intraerythrocytic parasites. We suggest a model in which V-PPase localised to the malaria parasite plasma membrane may serve as an electrogenic pump utilising pyrophosphate as an energy source, thus sparing the more precious ATP. Searching for V-PPase inhibitors could prove fruitful as a novel means of antiparasitic chemotherapy.

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Collaboration types
Domestic collaboration
Web of Science research areas
Parasitology
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