May function as a regulator of both motility- and head-associated functions such as capacitation and the acrosome reaction. Interacts with ROPN1 AND ROPN1L. Interacts with QRICH2 (By similarity). Ribs of the fibrous sheath in the principal piece of the sperm tail. Dorsal margin of the acrosomal segment. RII-binding site, predicted to form an amphipathic helix, could participate in protein-protein interactions with a complementary surface on the R-subunit dimer. Phosphorylated on tyrosine. Belongs to the AKAP110 family.