Characterization of human sperm binding to homologous recombinant zona pellucida proteins.

The union between mammalian gametes begins with the sperm binding to the zona pellucida (ZP). We studied the interaction between human sperm and ZP by using recombinant human ZP proteins (rhZP). The cDNAs coding for human ZP2, ZP3, and ZP4 were expressed in Sf9 cells and proteins were characterized to determine their competence for sperm binding.