Modification of simian virus 40 large tumor antigen by glycosylation.
The SV40-encoded transforming protein, large tumor antigen (T-ag), is multifunctional. Chemical modifications of the T-ag polypeptide may be important for its multifunctional capacity. T-ag is additionally modified by glycosylation. T-ag was metabolically labeled in SV40-infected cells with tritiated galactose or glucosamine, but not with mannose or fucose. The identity of glycosylated T-ag was established by immunoprecipitation with a variety of T-ag-specific antisera, including monoclonal antibodies. Incorporation of labeled sugar into T-ag was inhibited in the presence of excess unlabeled sugars, but not in the presence of excess unlabeled amino acids. Labeled monosaccharides could be preferentially removed from T-ag with a mixture of glycosidic enzymes. In addition, galactose was removed from purified T-ag by acid hydrolysis and identified as such by thin-layer chromatography. T-ag oligosaccharides were resistant to treatment with EndoH, and glycosylation was not inhibited by tunicamycin. Together, these data strongly suggest that T-ag is glycosylated. Several characteristics, including lack of mannose labeling, EndoH resistance, and tunicamycin resistance, suggest that T-ag is not an N-linked glycoprotein. Rather, these properties are more consistent with the identification of T-ag as an O-linked glycoprotein.
D000118:Acetylglucosaminidase / Q000378:metabolism; D000911:Antibodies, Monoclonal; D000957:Antigens, Viral, Tumor / Q000032:analysis* / Q000276:immunology; D005690:Galactose / Q000378:metabolism; D005944:Glucosamine / Q000378:metabolism; D006023:Glycoproteins / Q000032:analysis*; D008358:Mannose / Q000378:metabolism; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; D008970:Molecular Weight; D013539:Simian virus 40 / Q000276:immunology*; D014415:Tunicamycin / Q000494:pharmacology
D000911:Antibodies, Monoclonal; D000957:Antigens, Viral, Tumor; D006023:Glycoproteins; D014415:Tunicamycin; D000118:Acetylglucosaminidase; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; D005944:Glucosamine; D008358:Mannose; D005690:Galactose