Figure 3.

Possible mechanism of mammalian zona pellucida (ZP) hardening. Whereas ovastacin‐dependent cleavage of the ZP‐N2 domain could induce a conformational change of the ZP2 N‐terminus that leads to new protein–protein interactions, binding of zinc ions to ZP1 ZP‐N1 (based on PDB ID 6GF7) may alter the conformation of ZP filament cross‐links. Together with other ZP modifications discussed in the text, these molecular events could cause tighter interaction between adjacent ZP filaments, resulting in compaction of the supramolecular structure of the egg coat. Modified from (Monné & Jovine, 2011). Activated ovastacin is indicated by a blue Pac‐Man‐like symbol