After the first recognition occurs between the activated sperm and zona pellucida of the oocyte from the mammalians, β-1,4-galactosyltransferase I (β 4GalT I) combines the N-GlcNAc terminals by O-ligands on the ZP3 of the zona pellucida, which plays a difunctional role in the fertilization. The G protein signal system on the sperm membrane then is consequently activated by ZP3 via β4GalT I, contributing to the induction of acrosome reaction. It was proved that in the activation of the G protein system, both the BBXB and BBXXB motifs on the N terminal of the long β 4GalT I are necessary.
