Binding of recombinant pig zona pellucida protein 1 (ZP1) to acrosome-reacted spermatozoa

In an immunofluorescent study, recombinant pig zona pellucida protein 1 (pZP1) produced in Escherichia coli bound to acrosome-reacted spermatozoa from five different mammals. The location of the binding site moved from the equatorial region to the midpiece and tail regions during the incubation. This finding suggests that pig ZP1 acts as a secondary sperm-binding receptor in an interspecies manner and assists penetration of the spermatozoa through the zona pellucida. The recombinant pZP1 bound to 55 kDa protein (proacrosin) and 40 kDa protein of the boar spermatozoa as revealed by immunoblotting.