The function of ATP1A4 (ATPase Na+/K+ transporting subunit alpha 4, ENSG00000132681) is as follows. Sperm-specific catalytic alpha subunit of the Na(+)/K(+)- ATPase responsible for ATP-dependent Na(+)/K(+) exchange across the plasma membrane. Transports 3 Na(+) ions out of the cell and 2 K(+) ions into the cell for each ATP hydrolyze (PubMed:16861705). Plays an essential for sperm motility, capacitation, and male fertility by maintaining ionic gradients required for flagellar function and signaling (By similarity). {ECO:0000250|UniProtKB:Q9WV27, ECO:0000269|PubMed:16861705}.