Voltage-gated calcium channel that plays a central role in sperm cell hyperactivation. Controls calcium entry to mediate the hyperactivated motility, a step needed for sperm motility which is essential late in the preparation of sperm for fertilization. Activated by intracellular alkalinization. In contrast to the human ortholog, not activated by progesterone. Component of the CatSper complex or CatSpermasome composed of the core pore-forming members CATSPER1, CATSPER2, CATSPER3 and CATSPER4 as well as auxiliary members CATSPERB, CATSPERG2, CATSPERD, CATSPERE, CATSPERZ, C2CD6/CATSPERT, SLCO6C1, TMEM249, TMEM262 and EFCAB9 (PubMed:34225353, PubMed:21224844, PubMed:17478420, PubMed:19516020, PubMed:17227845, PubMed:34998468). HSPA1 may be an additional auxiliary complex member (PubMed:17478420, PubMed:19516020). The core complex members CATSPER1, CATSPER2, CATSPER3 and CATSPER4 form a heterotetrameric channel (PubMed:34225353). The auxiliary CATSPERB, CATSPERG2, CATSPERD and CATSPERE subunits form a pavilion-like structure over the pore which stabilizes the complex through interactions with CATSPER4, CATSPER3, CATSPER1 and CATSPER2 respectively (PubMed:34225353). SLCO6C1 interacts with CATSPERE, and TMEM262/CATSPERH interacts with CATSPERB, further stabilizing the complex (PubMed:34225353). C2CD6/CATSPERT interacts at least with CATSPERD and is required for targeting the CatSper complex in the flagellar membrane (PubMed:34998468). Interacts with Ca(v)3.3/CACNA1I, leading to suppression of T-type calcium channel activity (By similarity). Specifically located in the principal piece of the sperm tail. Testis-specific. Detected only after round spermatids are produced approximately at day 18. Mice are normal but males are sterile. Male sterility is due to defects in sperm motility unability to fertilize intact eggs. In mice lacking Catsper1, sperm lacks CatSper2 protein, while in mice lacking CatSper1, sperm lacks CatSper1 protein, suggesting that stable expression of CatSper1 protein requires CatSper2 and vice versa. Belongs to the cation channel sperm-associated (TC 1.A.1.19) family.