Detection of Glycoproteins in Gels and Blots

Abstract

As we become more aware of the significance of posttranslational modifications, such as glycosylation, in the production of recombinant proteins and in the proteomic studies of development and disease, techniques for the identification and characterization of the oligosaccharides attached to proteins need to be established.

After separation of the proteins by either one-diemensional-(1D)- or two-dimensional-(2D)-polyacrylamide gel electrophoresis (PAGE), the initial step is to identify which proteins are glycoproteins so that further characterization can proceed. Various methods have been developed since the early detection of glycoproteins on gels (1) and blots, with color, fluorescence, and lectin detection now carried out at the analytical level. The actual level of detection of course depends on the extent of glycosylation of the protein, as the reagents react only with the carbohydrate moiety. We have chosen to describe here the stains that we have found to be the most useful for visualizing glycoproteins, both on gels and blots, after separation by electrophoresis. It should be noted that all the staining procedures currently in use destroy the structure of the carbohydrate and thus prevent further analysis of the glycan component once the glycoprotein is visualized.