Mammalian homologues of the transient receptor potential (trp) gene product from Drosophila melanogaster function as Ca2+-selective or non-selective cation channels. Complementary DNA was isolated from a bovine testis cDNA library which encodes bovine trp2 (btrp2), a protein of 432 amino acid residues comprising four predicted transmembrane segments. Btrp2 mRNA is expressed in bovine testis, spleen and liver but not in brain, heart, adrenal gland or retina. In bovine testis expression of btrp2 mRNA is restricted to spermatocytes but is not present in spermatogonia, Leydig or Sertoli cells suggesting that btrp2 may contribute to the formation of ion channels in sperm cells.