Calcium/calmodulin-regulated and magnesium-dependent enzyme that catalyzes the hydrolysis of ATP coupled with the transport of calcium out of the cell (By similarity). By regulating sperm cell calcium homeostasis, may play a role in sperm motility (PubMed:15078889). ATP + Ca(2+)(in) + H2O = ADP + Ca(2+)(out) + H(+) + phosphate Activated by calcium/calmodulin. Interacts with PDZD11. Interacts with SLC35G1 and STIM1. Interacts with calmodulin. Specifically expressed by sperm in testis (at protein level). Male mice lacking Atp2b4 are infertile with severe reduction of sperm motility. Belongs to the cation transport ATPase (P-type) (TC 3.A.3) family. Type IIB subfamily.