Definition:

ATP-driven pump that supplies the Golgi apparatus with Ca(2+) and Mn(2+) ions, both essential cofactors for processing and trafficking of newly synthesized proteins in the secretory pathway. Within a catalytic cycle, acquires Ca(2+) or Mn(2+) ions on the cytoplasmic side of the membrane and delivers them to the lumenal side. The transfer of ions across the membrane is coupled to ATP hydrolysis and is associated with a transient phosphorylation that shifts the pump conformation from inward-facing to outward-facing state. Induces Ca(2+) influx independently of its ATP-driven pump function. At the basolateral membrane of mammary epithelial cells, interacts with Ca(2+) channel ORAI1 and mediates Ca(2+) entry independently of the Ca(2+) content of endoplasmic reticulum or Golgi stores. May facilitate transepithelial transport of large quantities of Ca(2+) for milk secretion via activation of Ca(2+) influx channels at the plasma membrane and active Ca(2+) transport at the Golgi apparatus.