Sperm-specific sodium/hydrogen exchanger involved in intracellular pH regulation of spermatozoa. Required for sperm motility and fertility. Involved in sperm cell hyperactivation, a step needed for sperm motility which is essential late in the preparation of sperm for fertilization. Required for the expression and bicarbonate regulation of the soluble adenylyl cyclase (sAC) (By similarity). Interacts with soluble adenylyl cyclase (sAC). The ion transport-like region is related to the membrane segments of voltage-gated ion channels. Its function is unknown (By similarity). Belongs to the monovalent cation:proton antiporter 1 (CPA1) transporter (TC 2.A.36) family.