A Kinase Anchor Protein 3 (AKAP3)

A Kinase Anchor Protein 3 contains an RII-binding domain, and is predicted to participate in protein-protein interactions with the R-subunit of the PKA. This protein is localized to the ribs of the fibrous sheath in the principal piece of the sperm tail. It may function as a regulator of both motility- and head-associated functions such as capacitation and the acrosome reaction. Spermatozoa stained with anti-AKAP3 exhibited intense fluorescence of the anterior acrosome and along the entire flagellum of bovine sperm, suggesting that AKAP3 associates with both the RI and RII subunits of PKA. The deduced 853-amino acid protein has 4 N-glycosylation sites, 26 phosphorylation sites, 8 N-myristoylation sites, and 1 amidation site. Northern blot analysis revealed expression of an approximately 3-kb transcript in testis only.