A plasma membrane-type Ca(2+)-ATPase co-localizes with a vacuolar H(+)-pyrophosphatase to acidocalcisomes of Toxoplasma gondii.
Ca(2+)-ATPases are likely to play critical roles in the biochemistry of Toxoplasma gondii, since these protozoa are obligate intracellular parasites and the Ca(2+) concentration in their intracellular location is three orders of magnitude lower than in the extracellular medium. Here, we report the cloning and sequencing of a gene encoding a plasma membrane-type Ca(2+)-ATPase (PMCA) of T.gondii (TgA1). The predicted protein (TgA1) exhibits 32-36% identity to vacuolar Ca(2+)-ATPases of Trypanosoma cruzi, Saccharomyces cerevisiae, Entamoeba histolytica and Dictyostelium discoideum. Sequencing of both cDNA and genomic DNA from T.gondii indicated that TgA1 contains two introns near the C-terminus. A hydropathy profile of the protein suggests 10 transmembrane domains. TgA1 suppresses the Ca(2+) hypersensitivity of a mutant of S.cerevisiae that has a defect in vacuolar Ca(2+) accumulation. Indirect immunofluorescence and immunoelectron microscopy analysis indicate that TgA1 localizes to the plasma membrane and co-localizes with the vacuolar H(+)-pyrophosphatase to intracellular vacuoles identified morphologically and by X-ray microanalysis as the acidocalcisomes. This vacuolar-type Ca(2+)-ATPase could play an important role in Ca(2+) homeostasis in T.gondii.
Laboratory of Molecular Parasitology, Department of Pathobiology, University of Illinois at Urbana-Champaign, 2001 South Lincoln Avenue, Urbana, IL 61802, USA.
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Luo
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Vieira
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Graves
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Zhong
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Moreno
D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D000252:Calcium-Transporting ATPases / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D002462:Cell Membrane / Q000201:enzymology*; D004023:Dictyostelium / Q000201:enzymology; D004748:Entamoeba histolytica / Q000201:enzymology; D007150:Immunohistochemistry; D008969:Molecular Sequence Data; D010766:Phosphorylation; D017494:Proton Pumps / Q000378:metabolism; D006180:Proton-Translocating ATPases / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014122:Toxoplasma / Q000166:cytology / Q000201:enzymology* / Q000235:genetics; D014349:Trypanosoma cruzi / Q000201:enzymology; D025262:Vacuolar Proton-Translocating ATPases; D014617:Vacuoles / Q000201:enzymology / Q000648:ultrastructure
D017494:Proton Pumps; D000255:Adenosine Triphosphate; D025262:Vacuolar Proton-Translocating ATPases; D006180:Proton-Translocating ATPases; D000252:Calcium-Transporting ATPases