A study of lectin-binding to the water-insoluble proteins of the lens.

Binding of lectins to the water-insoluble fractions from human, monkey and mouse lenses was investigated. Lectins bound to glycoproteins blotted from SDS-polyacrylamide gels onto nitrocellulose paper. Use of multiple lectins showed that glycoproteins with apparent molecular weights of about 120 000 and 90 000 were present in all species. These proteins were found in the urea-insoluble fraction. Multiple lectins also bound to two bands around 67 000 and 63 000 molecular weight in both human and monkey lens fractions as well as a urea-soluble band at about 140 000. A 35 000 MW glycoprotein containing N-acetyl-galactosamine and fucose sugars was present in the capsule-epithelium of monkey lenses but was not detected in cortical or nuclear fractions. Glycoproteins from normal and cataractous mice were identified using this new methodology and compared with previously published work using sodium borohydride labelling of glycoproteins. Because of the numerous glycoproteins that can be detected and the ability to assign sugar residues to individual proteins, the lectin-binding method is a powerful tool to investigate lens glycoproteins.