Fig. 6. Chronology of fertilization envelope formation. Diagram of the time-course of fertilization envelope assembly and modification of the egg cortex, starting from sperm fusion to ovoperoxidase-dependent crosslinking. Milestones (1-6) are detailed in the text. In panel 6, the dashed line denotes non-covalent interaction whereas the solid line denotes dityrosine crosslinking between proteins. CGSP1, cortical granule serine protease 1 (proCGSP1 indicates the zymogenic form); OVOP, ovoperoxidase (ovop indicates the zymogenic form); TG, transglutaminase; Udx1, urchin dual oxidase 1; RDZ, rendezvin; PLN, proteoliaisin; H₂O₂, hydrogen peroxide; "R-Q=K-R", covalent epsilon (gamma-glutamyl)lysine bonds; "R-Y=Y-R", covalent dityrosine crosslink; 40 kDa, macromolecules of 40,000 daltons.