Vitelline coat of Unio elongatulus: II. Biochemical properties of the 220- and 180-kD components

In a previous study we found that two glycoproteins with apparent molecular weights of 220 kD and 180 kD account for 80-90% of the material dissolved from the vitelline coat of the egg of the bivalve mollusk, Unio elongatulus (Focarelli and Rosati, 1993: Mol Reprod Dev 35:44-51). In this study we isolated and purified these glycoproteins by electroelution. The two proteins differ in many respects: the 180-kD molecule is acidic in nature and highly heterogeneous, whereas the 220-kD protein is neutral and less heterogeneous. Both seem to have O- and N-linked oligosaccharide chains. The 180-kD protein contains 13-16% carbohydrate, whereas the 220-kD molecular contains only 7-8%. Amino acid analysis and peptide mapping also show that each protein represents a unique polypeptide chain.