Nucleic acid and protein sequences relating to a cation channel which is sperm-specific (CatSper3) are disclosed. The CatSper3 protein is shown to be specifically expressed in sperm. Nucleic acids, vectors, transformed cells, transgenic animals, polypeptides, and antibodies relating to the CatSper3 gene and protein are disclosed. Also provided are methods of in vitro fertilization and contraception, methods of identifying modulators of CatSper3 activity, methods of genotyping subjects with respect to CatSper3, and methods of diagnosing and treating CatSper3-mediated disorders, including infertility. Related business methods are also disclosed.