LOCALIZATION OF CORTICAL GRANULE LECTIN LIGAND IN XENOPUS-LAEVIS EGG JELLY

The block to polyspermy in Xenopus laevis involves an interaction betw een a cortical granule lectin, released at fertilization, and a ligand located in the egg extracellular matrix. The egg extracellular matrix in X. laevis consists of a vitelline envelope and three distinct jell y layers, designated J1, J2 and J3. To localize cortical granule lecti n ligand in the egg extracellular matrix, we used enzyme-linked lectin assays that showed that cortical granule lectin ligands were absent i n J2, J3 and the vitelline envelope. Cortical granule lectin bound to a ligand(s) in J1 in a galactose-dependent fashion. In addition, we se parated egg jelly macromolecules electrophoretically and, in conjuncti on with western blotting, have shown that J1 contains two major, high molecular weight ligands for cortical granule ligand. Finally, using c onfocal microscopy, we demonstrated that the ligand(s) for cortical gr anule lectin occupies a 20-30 mu m thick band in a region of J1 just p roximal to the vitelline envelope.