Purification and characterization of a 38-kDa protein, sp38, with zona pellucida-binding property from porcine epididymal sperm.

A 38-kDa protein, sp38, was purified from the detergent extract of porcine epididymal sperm. Sp38 showed zona pellucida-binding properties similar to those of proacrosin. These two proteins specifically bound to the 90-kDa glycoprotein form of the zona pellucida components in a calcium-dependent manner. The binding of sp38 to the zona pellucida glycoprotein was inhibited by proacrosin. These findings suggest that the two proteins competitively interact with the zona pellucida during the early stage of fertilization.