Preparation and purification of a structural sialofucoglycoprotein from the bovine lens capsule

When bovine lens capsules are exhaustively digested with collagenase a protein fraction remains that contains about 10% carbohydrate consisting of hexosamine, hexose, fucose and neuraminic acid. When treated with β-mercaptoethanol most of the carbohydrate goes into solution and remains so after dialysis. A fraction of this material precipitated by 80% acetone shows at pH 4·5 only one sharp band in polyacrylamide gel electrophoresis, but disintegrates into a more diffuse band with rising pH. The molecular size determination by SDS polyacrylamide gel electrophoresis shows four subunits with the maximum MW of about 35,000. Molecular sieve chromatography at pH 4·5 indicates a MW between 75,000–150,000. The ultracentrifuge sedimentation mobility at pH 4·5, however, indicates a MW of only about 35,000 suggesting a disrupting of the molecule by hydrostatic pressure. The ratio of the concentration of the structural glycoprotein to that of collagen is twice as high in the posterior as in the anterior lens capsule.