Detection, quantification and characterization of ß-Galactoside-binding lectins from Bufo arenarum

S-type lectins from Bufo arenarum ovary and blastula embryos (8-16 blastomeres) were purified. These proteins showed p-galactoside-binding specificity, Caw-independency and the requirement of thiol-reducing agents to maintain their hemagglutinating activity. Lectin activity showed to be developmentally regulated in Bufo arenarum embryos. Subunit molecular weights proved to be of 15 kDa for both lectins. Native molecular masses were of 30 and 32 kDa, for the ovary and the blastula lectin, respectively. Both lectins showed to be homodimers with non-covalently bound subunits. Isoelectrical points were 4,O and 4,7, for the ovary and the blastula lectin, respectively. Both lectins showed very strong immunological cross-reactivity, which suggests primary sequence homologies. Immunohistochemical studies demonstrated the localization of the embryonic lectin in the fertilization envelope, yolk platelets and celullar surfaces. Biological activities such as the block of the polispenny or adhesive-antiadhesive effects were suggested for these S-type lectins. Peptide or cDNA-sequencing information would be needed to classified them as galectins, and to determine the degree of homology between both.Fil:Elola, María Teresa. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina