Catalyzes the hydrolysis of ATP coupled with the transport of calcium. Has some hydrolysis activity also with dATP, GTP, UTP, ITP and 4-nitrophenyl phosphate as substrate. No activity with ADP, CTP, acetyl dihydrogen phosphate or AMP-PNP as substrate. ATP + Ca(2+)(in) + H2O = ADP + Ca(2+)(out) + H(+) + phosphate Completely inhibited by vanadate(3-). Also inhibited by lanthanoid atom and phosphate. Not inhibited by N-ethylmaleimide, 1,3-dicyclohexylcarbodiimide, oligomycin, ouabain, valinomycin, nigericin, thapsigargin, cyclopiazonic acid or fluorescein isothiocyanate. Optimum pH is 8.0 for ATP hydrolysis activity. Loses 50% of the activity at pH 7.0 or 8.5, has less than 20% activity at pH 6.5 and virtually no activity at pH 9.0. Extended N-terminus.