Carbohydrate-mediated Adhesion of Eggs and Sperm during Mammalian Fertilization

The process of fertilization in mammals is initiated by species-specific binding of free-swimming sperm to ovulated eggs. The search for gamete surface components that support species-specific binding of sperm to eggs in mammals has led to the conclusion that the process is mediated by protein-carbo-hydrate interactions. Apparently, specific oligosaccharides associated with a glycoprotein (sperm receptor) located in the egg extracellular coat (zona pellucida) are recognized by a protein (egg-binding protein) located in the sperm head plasma membrane. In this article, some of the evidence that supports this conclusion is reviewed.