Major structural component of sperm fibrous sheath. Plays a role in sperm motility (PubMed:12167408). Interacts with PRKAR1A and PRKAR2A (PubMed:9852104). Interacts with ENO4 (PubMed:23446454). Localizes to the principle piece of the sperm flagellum. Spermatid. Post-meiotic phase of spermatogenesis. RI-alpha binding site, predicted to form an amphipathic helix, could participate in protein-protein interactions with a complementary surface on the R-subunit dimer. Belongs to the AKAP110 family.