Calcium/calmodulin-regulated and magnesium-dependent enzyme that catalyzes the hydrolysis of ATP coupled with the transport of calcium out of the cell (PubMed:8530416). By regulating sperm cell calcium homeostasis, may play a role in sperm motility (By similarity). ATP + Ca(2+)(in) + H2O = ADP + Ca(2+)(out) + H(+) + phosphate Activated by calcium/calmodulin. Interacts with PDZD11 (PubMed:12763866). Interacts with SLC35G1 and STIM1 (PubMed:22084111). Interacts with calmodulin (PubMed:2963820, PubMed:10493800). There is a combination of two alternatively spliced domains at N-terminal site A (X and Z) and at C-terminal site B/C (A, B, D and K). The splice sites have mostly been studied independently. Full isoforms so far detected are isoform XA and isoform XB. Experimental confirmation may be lacking for some isoforms. Isoform XB is the most abundant isoform and is expressed ubiquitously. Isoforms containing segment Z have only been detected in heart, while isoforms containing segment a have been found in heart, stomach and brain cortex. Belongs to the cation transport ATPase (P-type) (TC 3.A.3) family. Type IIB subfamily.