Major protein component of the posterior mating plug. Accessory gland proteins constitute, or are required for formation of the anterior mating plug. Posterior mating plug forms before sperm transfer and the anterior mating plug is formed after the start of mating. Specifically expressed in the ejaculatory bulb and seminal fluid. Detected in mated females 3 minutes after the start of mating, and for at least 3 hours after the start of mating.