Sperm-specific Na(+)/H(+) exchanger involved in intracellular pH regulation of spermatozoa. Involved in sperm motility and fertility. Expressed only in the testis. May be produced at very low levels due to a premature stop codon in the mRNA, leading to nonsense-mediated mRNA decay. May be produced at very low levels due to a premature stop codon in the mRNA, leading to nonsense-mediated mRNA decay. Belongs to the monovalent cation:proton antiporter 1 (CPA1) transporter (TC 2.A.36) family.