An intracellular ATP-dependent calcium pump within the yeast Schizosaccharomyces pombe, encoded by the gene cta3.

We have permeabilized the plasma membranes of Schizosaccharomyces pombe cell with nystatin and measured ATP-dependent Ca2+ uptake in the presence of KNO3 and a protonophore in order to inhibit Ca2+ uptake into the vacuole. ATP-dependent Ca2+ accumulation into non-vacuolar Ca(2+)-storing organelles was detected. This Ca2+ uptake activity was maximal at pH 6 and inhibited by vanadate, the inhibitor of P-type ATPases. The null mutation of cta3, a putative Ca2+ gene, [Ghislain, M., Goffeau, A., Halachmi, D. and Eilam, Y. (1990) J. Biol. Chem. 265, 18400-18407] strongly reduced the level of ATP-dependent Ca2+ uptake into non-vacuolar intracellular storing organelles. This result suggests that cta3 encodes an intracellular ATP-dependent Ca2+ pump. The residual ATP-dependent Ca2+ uptake in the mutant strain indicated the presence of a second nonvacuolar, intracellular Ca(2+)-ATPase encoded by a different gene.