Physiological studies on the sperm surface component responsible for sperm-egg bonding in sea urchin fertilization : I. Effect of sperm-binding protein on the fertilizing capacity of sperm

When sea urchin sperm is pretreated with sperm-binding protein prepared from the vitelline membrane of eggs of homologous species, it loses its fertilizing capacity entirely without losing its motility. It is not affected at all by sperm-binding protein from heterologous species. Neither agglutination nor acrosome reaction is evoked by the pretreatment. It is suggested that the sea urchin spermatozoon has on the apical part of its head a component which is complementary to the sperm-binding protein of the egg, and that the observed loss of the fertilizing capacity is caused by antedated interaction of this component with sperm-binding protein added before insemination.