ZP3

ZP3, or zona pellucida glycoprotein 3, is a secreted glycoprotein that is a component of the zona pellucida, the extracellular matrix surrounding mammalian oocytes. It is encoded by the ZP3 gene and belongs to the zona pellucida protein family, which includes ZP1–ZP4. ZP proteins share a conserved ZP domain that drives polymerization into a network forming the zona pellucida.

ZP3 is synthesized by the oocyte during growth and secreted into the extracellular space, where it assembles with ZP1, ZP2, and ZP4 to create the zona pellucida. The matrix provides structural organization and serves as the primary site for sperm interaction in many species.

In fertilization, ZP3 participates in sperm recognition and can trigger the acrosome reaction. The interaction is mediated in part by carbohydrate residues on ZP3, and glycosylation status influences species-specific sperm binding. The precise role of ZP3 as a sperm receptor can vary among species, with some systems emphasizing contributions from ZP2 or from multiple zona proteins.

ZP3 also helps determine the properties of the zona pellucida that influence fertilization regulation and the prevention of polyspermy after fertilization, through post-fertilization matrix modifications.

In humans and other mammals, alterations in ZP3 expression or structure can affect fertility and contribute to zona pellucida defects. ZP3 and ZP3-derived peptides are widely used in fertilization research and immunocontraception studies, making the gene a focus in reproductive biology and related biomedical research.