SIALOGLYCOPROTEINS WITH A HIGH AMOUNT OF O-GLYCOSIDICALLY LINKED CARBOHYDRATE MOIETIES STAIN YELLOW WITH SILVER IN SODIUM DODECYL-SULFATE POLYACRYLAMIDE GELS

Several sialoglycoproteins and human salivary proteins were analyzed in sodium dodecyl sulfate-polyacrylamide gels using the silver/Coomassie-staining protocol (J.K. Dzandu, M.E. Deh, D.L. Barratt, and G.E. Wise, 1984, Proc. Natl. Acad. Sci. USA 81, 1733-1737) to determine the extent to which yellow Ag staining originally reported for human red blood cell glycophorins can be applied to other sialoglycoproteins. Results showed that not all sialoglycoproteins elicit a positive yellow color in the silver stain reaction. Some of the sialoglycoproteins stained as brown or negative images in the Ag-staining cycle. Alkaline .beta. elimination of O-glycosidically linked carbohydrate chains of glycophorin resulted in the loss of yellow color development in the Ag-staining protocol. Analysis of acidic salivary proteins showed several yellow Ag-stained bands at Mr .times. 10-3 = 150, 82,70,51,46 and 42. These results suggest that the carbohydrate moieties of glycophorin removable by alkaline .beta.-elimination are responsible for the characteristic yellow color in the Ag stain reaction. In addition, under our staining conditions sialoglycoproteins with a high amount of O-glycosidically linked carbohydrate chains give a characteristic yellow silver stain.