title: Localization of the phosphorylations of polyomavirus large T antigen.
abstract: Polyomavirus large T antigen is phosphorylated on both serine and threonine residues at a ratio of approximately 6 to 1. This phosphorylation could be resolved into a series of nine Staphylococcus aureus V8 phosphopeptides. All of these were found in an N-terminal chymotryptic fragment with a molecular weight of 57,000. A C-terminal formic acid fragment of 50,000-molecular-weight lacked phosphate. Therefore, unlike simian virus 40 large T antigen, polyomavirus large T antigen has no significant C-terminal phosphorylation. Limited V8 and hydroxylamine cleavage showed that the phosphorylations can be localized to two different portions of the molecule. A significant fraction of the phosphate was localized in the N-terminal portion of the molecule before residue 183. Within this region V8 peptides 4, 8, and 9 represented phosphorylations that were more proximal, while peptides 1, 2, and 3 included more distal phosphorylations. None of these phosphorylations appeared analogous to those of simian virus 40 large T antigen. V8 phosphopeptides 5 and 7 were more distal and could be distinguished in biological experiments from the N-terminal phosphorylations. Formic acid mapping suggested that much, if not all, of this phosphorylation is located between residues 257 and 285.
mesh_terms: D000818:Animals; D000952:Antigens, Polyomavirus Transforming; D000957:Antigens, Viral, Tumor / Q000235:genetics; D002478:Cells, Cultured; D051379:Mice; D008970:Molecular Weight; D009154:Mutation; D009856:Oncogene Proteins, Viral / Q000235:genetics; D010446:Peptide Fragments / Q000032:analysis; D010766:Phosphorylation; D010768:Phosphoserine / Q000032:analysis; D010769:Phosphothreonine / Q000032:analysis; D011120:Polyomavirus / Q000201:enzymology* / Q000235:genetics; D011494:Protein Kinases
chemical_list: D000952:Antigens, Polyomavirus Transforming; D000957:Antigens, Viral, Tumor; D009856:Oncogene Proteins, Viral; D010446:Peptide Fragments; D010769:Phosphothreonine; D010768:Phosphoserine; D011494:Protein Kinases