The CATSPER (cation channel of sperm) complex is a tetrameric complex consisting of CATSPER1, CATSPER2, CATSPER3 and CATSPER4, it functions as an alkalinisation-activated calcium channel. This complex requires several auxiliary subunits, including CATSPERD. CATSPERD is essential for the cation channel function and may play a role in channel assembly or transport [1].

1: A novel gene required for male fertility and functional CATSPER channel formation in spermatozoa. Chung JJ, Navarro B, Krapivinsky G, Krapivinsky L, Clapham DE; Nat Commun. 2011;2:153. PMID:21224844