title: Characterisation of an intracellular Ca2+ pump in Dictyostelium.
abstract: 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.
authors.affiliation: Laboratoire de Biologie Cellulaire (URA 1130 CNRS), CEA, Département de Biologie, Moléculaire et Structurale, Centre d'Etudes Nucléaires de Grenoble, France.
authors.forename: E K
authors.initials: EK
authors.lastname: Rooney
authors.forename: J D
authors.initials: JD
authors.lastname: Gross
authors.forename: M
authors.initials: M
authors.lastname: Satre
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002451:Cell Compartmentation; D002499:Centrifugation, Density Gradient; D004023:Dictyostelium / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism*; D007425:Intracellular Membranes / Q000378:metabolism*; D008861:Microsomes / Q000378:metabolism; D009550:Nigericin / Q000494:pharmacology; D010070:Oxalates / Q000494:pharmacology; D006180:Proton-Translocating ATPases / Q000378:metabolism; D011522:Protons; D015800:Protozoan Proteins / Q000378:metabolism*; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin; D014617:Vacuoles / Q000201:enzymology; D014638:Vanadates / Q000494:pharmacology
chemical_list: D005656:Fungal Proteins; D010070:Oxalates; D011522:Protons; D015800:Protozoan Proteins; D013729:Terpenes; D014638:Vanadates; D019284:Thapsigargin; D006180:Proton-Translocating ATPases; D000252:Calcium-Transporting ATPases; D009550:Nigericin; D002118:Calcium