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Cell Calcium. 1994 Dec;16(6):509-22.

Characterisation of an intracellular Ca2+ pump in Dictyostelium.

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Laboratoire de Biologie Cellulaire (URA 1130 CNRS), CEA, Département de Biologie, Moléculaire et Structurale, Centre d'Etudes Nucléaires de Grenoble, France.


Calcium uptake by microsomal membranes from the cellular slime mould Dictyostelium discoideum was measured using Calcium Green-2 as a fluorescent probe of external free Ca2+ concentration. High-affinity Ca2+ uptake was found to be completely inhibited by low concentrations of vanadate, but not by thapsigargin, suggesting that the activity is mediated by a Ca(2+)-ATPase distinct from sarco(endo)plasmic reticulum type of higher animal cells. On sucrose density gradients, Ca2+ uptake distributes with vacuolar proton pump activity and part of the observed Ca2+ uptake is dependent on the pH gradient generated by the vacuolar-type H(+)-ATPase, indicating that the Ca2+ pump is located on both acidic and non-acidic vesicles, possibly derived from the H(+)-ATPase-rich contractile vacuole complex.

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