title: Detection and localization of a Ca2+-ATPase activity in Toxoplasma gondii.
abstract: Toxoplasma gondii, the agent causing toxoplasmosis, is an obligate intracellular protozoan parasite. A calcium signal appears to be essential for intracellular transduction during the active process of host cell invasion. We have looked for a Ca2+-transport ATPase in tachyzoites and found Ca2+-ATPase activity (11-22 nmol Pi liberated/mg protein/min) in the tachyzoite membrane fraction. This ATP-dependent activity was stimulated by Ca2+ and Mg2+ ions and by calmodulin, and was inhibited by pump inhibitors (sodium orthovanadate or thapsigargin). We used cytochemistry and X-ray microanalysis of cerium phosphate precipitates and immunolabelling to find the Ca2+, Mg2+-ATPase. It was located mainly in the membrane complex, the conoid, nucleus, secretory organelles (rhoptries, dense granules) and in vesicles with a high calcium concentration. Thus, Toxoplasma gondii possesses Ca2+-pump ATPase (Ca2+, Mg2+-ATPase) as do eukaryotic cells.
authors.affiliation: UPRES EA 2070 et Laboratoire de Parasitologie-Mycologie, CHU Maison Blanche, Reims, France. annie.bonhomme@univ-reims.fr
authors.forename: A
authors.initials: A
authors.lastname: Bouchot
authors.forename: J D
authors.initials: JD
authors.lastname: Jaillet
authors.forename: A
authors.initials: A
authors.lastname: Bonhomme
authors.forename: N P
authors.initials: NP
authors.lastname: Alessandro
authors.forename: P
authors.initials: P
authors.lastname: Laquerriere
authors.forename: L
authors.initials: L
authors.lastname: Kilian
authors.forename: H
authors.initials: H
authors.lastname: Burlet
authors.forename: J E
authors.initials: JE
authors.lastname: Gomez-Marin
authors.forename: M
authors.initials: M
authors.lastname: Pluot
authors.forename: P
authors.initials: P
authors.lastname: Bonhomme
authors.forename: J M
authors.initials: JM
authors.lastname: Pinon
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000032:analysis* / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004577:Electron Probe Microanalysis; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007150:Immunohistochemistry; D008274:Magnesium / Q000494:pharmacology; D008854:Microscopy, Electron; D016253:Microscopy, Immunoelectron; D011188:Potassium / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology; D014122:Toxoplasma / Q000201:enzymology* / Q000648:ultrastructure; D014638:Vanadates / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D014638:Vanadates; D019284:Thapsigargin; D000255:Adenosine Triphosphate; D000252:Calcium-Transporting ATPases; D008274:Magnesium; D011188:Potassium; D002118:Calcium