Localization and developmental fate of ovoperoxidase and proteoliaisin, two proteins involved in fertilization envelope assembly

Fertilization of the sea urchin egg leads to the assembly of an extracellular matrix, the fertilization envelope. Ovoperozidase, the enzyme implicated in hardening the fertilization envelope, is inserted into the assembling structure via a Ca²⁺-dependent interaction with the protein proteoliaisin (P. Weidman and B. M. Shapiro, 1987, J. Cell Biol. 105, 561-567). In the present report, polyclonal antisera were raised to ovoperoxidase and proteoliaisin (purified from eggs of Strongylocentrotus purpuratus) and characterized by Western blot analysis and an enzyme-linked immunoabsorbent assay (ELISA). By indirect immunofluorescence microscopy all cortical granules of unfertilized eggs, as well as the fertilization envelope, contained both proteoliaisin and ovoperozidase. At the ultrastructural level both proteins are localized to the electron-dense spiral lamellae of the cortical granules. Western blot analysis revelaed that ovoperoxidase and proteoliaisin persist in early embryos until hatching, but are absent from later developmental stages. Homogenates of eggs of several other echinoderm species (Strongylocentrotys droebachiensis, Strongylocentrotus franciscanus, Pisaster ochraceus, Dendraster excentricus, and Lytechinus pictus) also contain proteins antigenically similar to ovoperoxidase and proteoliaisin, indicating that many echinoderms utilize a similar strategy for assembly of the fertilization envelope. The results underline the need for postsecretory controls in the extracellular matrix modifications that accompany the cortical reaction.