Enables receptor ligand activity. A structural constituent of egg coat. Involved in several processes, including oogenesis; positive regulation of acrosome reaction; and regulation of gene expression. Acts upstream of or within binding activity of sperm to zona pellucida. Located in collagen-containing extracellular matrix and plasma membrane. Is expressed in ovary and testis. Orthologous to several human genes including ZP3 (zona pellucida glycoprotein 3). [provided by Alliance of Genome Resources, Apr 2022]