Abstract
High mobility group protein‐1 (HMG‐1) is a ubiquitous, highly conserved, and abundant nuclear protein. Recent findings suggest that HMG‐1 may serve as a DNA chaperone protein and play a role in the regulation of transcription. There is a mounting interest in elucidating the mechanism by which HMG‐1 protein takes part in these activities. HMG‐1 has been reported to undergo an extensive array of posttranslational modifications, including glycosylation. We extend the earlier findings on the glycosylation of HMG‐1 by quantitating the amount of carbohydrate on HMG‐1 from calf thymus and chicken erythrocytes isolated by 2 different purification procedures. In addition, 2 different developmental stages (embryonic and adult) were examined in the chicken erythrocytes. The glycosyl composition was quantitated using the Dionex HPAE‐PAD II system. Furthermore, the presence of O‐linked GlcNAc on HMG‐1 was determined by the enzymatic incorporation of ^3^H‐galactose into HMG‐1 protein. Contrary to earlier reports, less than 0.5 mol of total monosaccharides (Fuc, Man, GalNH~2~, GlcNH~2~, Gal) were detected per mole of HMG‐1 protein, regardless of the source of the protein or the method of isolation. In addition, less than 0.002 mol of O‐linked GlcNAc per mole of HMG‐1 protein was detected. Thus, insignificant amount of glycosylation was found on HMG‐1 protein. Because O‐linked GlcNAc modification of proteins is believed to be a reversible posttranslational event, more definitive studies will need to be conducted before ruling out that the function of HMG‐1 protein is not regulated by glycosylation.