Cylicin 1 (CYLC1)

Cylicin 1 contains numerous lysine dipeptides followed by a third variable amino acid (KKX), which in most cases is aspartic acid; these KKX tripeptides occur throughout the molecule, with the exception of the C-terminal tail, which contains proline-rich segments.

The central portion of the protein is arranged as a series of repeating units that are predicted to form individual short alpha helices, which are interrupted by short linker segments. Antibodies against human cylicin-1 reacted with 2 polypeptides of 60 kD and 80 kD by immunoblot analysis and stained specifically the calyx of human and bovine spermatozoa by immunofluorescence microscopy. Northern blot analysis of bovine tissues detected a cylicin-1 transcript only in testis.