Calicin (CCIN)

Calicin is missing or is arranged in a dramatically different pattern in the heads of malformed human spermatozoa such as teratozoospermias with 'round-headed' sperm or with other 'postacrosomal sheath defects.

The predicted bovine protein contains 588 amino acids and has a calculated pI of 8.1. The partial human cDNA encodes a protein that starts at a position corresponding to the fourth amino acid of bovine calicin. Overall, the 2 calicins are 91% identical. There are 3 consecutive repeats in the middle of the calicin protein. Sequence comparisons revealed that calicin shares homology with the Drosophila kelch protein, which is associated with the actin-rich intercellular bridges (ring canals) in the egg chamber that connect the oocyte and the nurse cells.