ZP2

The zona pellucida is an extracellular matrix that surrounds the oocyte and early embryo. It is composed primarily of three (mouse) or four (human) glycoproteins (ZP1-4) with various functions during fertilization and preimplantation development. The protein encoded by this gene is a structural component of the zona pellucida and functions in secondary binding and penetration of acrosome-reacted spermatozoa. The nascent protein contains a N-terminal signal peptide sequence, a conserved ZP domain, a consensus furin cleavage site, and a C-terminal transmembrane domain. It is hypothesized that furin cleavage results in release of the mature protein from the plasma membrane for subsequent incorporation into the zona pellucida matrix. However, the requirement for furin cleavage in this process remains controversial based on mouse studies. == 3D structure ==

The crystal structure of the sperm-binding domain of ZP2 at 0.95 Å resolution () showed that is shares the same ZP-N fold first identified in structures of ZP3 (). This provided experimental evidence for the suggestion that the N-terminal region of ZP2 consists of three ZP-N repeats and revealed that - despite insignificant sequence identity - ZP2 is structurally similar to VERL, the vitelline envelope receptor for egg lysin of the mollusk abalone (). This established a link between invertebrate and vertebrate fertilization by suggesting that, despite being separated by 600 million years of evolution, mollusk and human use a common protein fold to interact with sperm. == References ==