Responsible for physiological and behavioral changes in mated female flies. Associates with sperm and localizes to specific regions of the female reproductive tract, including the sperm storage organs. It accelerates sperm accumulation into storage but does not mediate the entry of the first sperm into storage. Once sperm storage has initiated it seems to act as a guidance factor helping subsequent sperm move into storage, a corral concentrating sperm around the SSO entrances and/or a trigger for responses within the female that accelerate storage of sperm. Detected in the male accessory glands (at protein level) (PubMed:24514904). Produced in the accessory glands and secreted into seminal fluid (PubMed:9474779). Proteolytically cleaved by the seminal metalloprotease Semp1 (PubMed:24514904). Cleavage appears to take place in the mated female (PubMed:24514904).