Carbohydrate modifications of the high mobility group proteins

This paper reports the results of numerous biochemical analyses which indicate that the "high mobility group" proteins (HMGs) of mouse and bovine cells are bona fide glycoproteins and can, in addition, be modified by poly(ADP-ribose) addition in vitro. The sugars N-acetylglucosamine, mannose, galactose, glucose, fucose, and one unknown sugar (possibly xylose) have been identified in purified preparations of HMGs 14 and 17. Furthermore, the fucose-specific lectin Ulex europeus agglutinin I bound both to the isolated HMGs and to monomer nucleosomes containing HMGs released from "active chromatin" by micrococcal nuclease digestion. Selective alkaline borohydride reductive cleavages of the HMGs suggested that the oligosaccharide prosthetic groups are primarily bound to these proteins by N-glycosidic linkages. The unexpected finding that the HMGs contain covalently bound complex carbohydrate moieties allows for a potentially great amount of variability and specificity in these proteins that may have important biological implications.