Detection and localization of a Ca2+-ATPase activity in Toxoplasma gondii.
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.
Bouchot
A
A
UPRES EA 2070 et Laboratoire de Parasitologie-Mycologie, CHU Maison Blanche, Reims, France. annie.bonhomme@univ-reims.fr
Jaillet
J D
JD
Bonhomme
A
A
Alessandro
N P
NP
Laquerriere
P
P
Kilian
L
L
Burlet
H
H
Gomez-Marin
J E
JE
Pluot
M
M
Bonhomme
P
P
Pinon
J M
JM
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
D004791:Enzyme Inhibitors; D014638:Vanadates; D019284:Thapsigargin; D000255:Adenosine Triphosphate; D000252:Calcium-Transporting ATPases; D008274:Magnesium; D011188:Potassium; D002118:Calcium