A protein on the surface of sperm is crucial to mammalian fertility in unexpected ways.

References: 

Primakoff, P. 1998. The function of ADAMs and the mechanism of sperm-egg fusion in fertilization. Annual meeting of the Society for Developmental Biology. June. Palo Alto, Calif.

Sources:

Paul Primakoff
University of California Davis School of Medicine
Department of Cell Biology/Anatomy
Davis, CA 95616