Coiled Coil Domain Containing Protein 65 (CCDC65)

CCDC65 is a sperm tail protein that is posttranslationally modified during sperm capacitation. The deduced 484-amino acid protein has a calculated molecular mass of 57 kD and contains 2 potential sites for N-glycosylation, 2 for N-myristoylation, and many potential phosphorylation sites. Western blot analysis detected high CCDC65 expression in adult human testis, but no detectable expression in fetal testis. Immunohistochemical studies of CCDC65 expression in spermatozoa detected protein primarily in the spermatocyte and spermatid, with weak expression in spermatogonia and no signal in Leydig cells. Immunofluorescence analysis detected CCDC65 throughout the entire sperm tail in human noncapacitated, capacitated, and acrosome-reacted spermatozoa.