Zona Pellucida Glycoprotein 1, Sperm Receptor (ZP1)

The mammalian zona pellucida is composed of 3 major glycoproteins, ZP1, ZP2, and ZP3. ZP3, the molecule responsible for the major sperm-receptor activity of the zona, plays a significant role in fertilization. ZP2 is implicated as a secondary sperm receptor that binds sperm only after the induction of the sperm acrosome reaction. See review by Dean (1992). The mature ZP1, ZP2, and ZP3 proteins have molecular weights of 90-110 kD, 64-76 kD, and 57-73 kD, respectively.

The zona pellucida (plural zonae pellucidae) is a glycoprotein membrane surrounding the plasma membrane of an oocyte. It is a vital constitutive part of the latter, external but of essential importance to it. The zona pellucida first appears in multilaminar primary oocytes.