Improved localization of phosphorylation sites in simian virus 40 large T antigen.
The location of phosphorylation sites in the large T antigen of simian virus 40 has been studied both by partial chemical cleavage and by partial proteolysis of various forms of large T. These included the full-size wild-type molecule with an apparent molecular weight of 88,000, deleted molecules coded for by the mutants dl1265 and dl1263, and several shortened derivatives generated by the action of a cellular protease. These molecules differed from each other by variations in the carboxy-terminal end. In contrast, a ubiquitous but minor large T form with a molecular weight of 91,000 was found to be modified in the amino-terminal half of the molecule. In addition to the phosphorylation of threonine at position 701 (K.-H. Scheidtmann et al., J. Virol. 38:59-69, 1981), two other discrete domains of phosphorylation were recognized, one at either side of the molecule. The amino-terminal region was located between positions 81 and 124 and contained both phosphothreonine and phosphoserine residues. The carboxy-terminal region was located between approximate positions 500 and 640 and contained at least one phosphoserine residue but no phosphothreonine. The presence in the phosphorylated domains of large T of known recognition sequences for different types of protein kinases is discussed, together with possible functions of large T associated with these domains.
D000956:Antigens, Viral / Q000032:analysis*; D000957:Antigens, Viral, Tumor; D010447:Peptide Hydrolases; D010748:Phosphopeptides / Q000032:analysis*; D010766:Phosphorylation; D010768:Phosphoserine / Q000032:analysis; D010769:Phosphothreonine / Q000032:analysis; D013539:Simian virus 40 / Q000276:immunology*
D000956:Antigens, Viral; D000957:Antigens, Viral, Tumor; D010748:Phosphopeptides; D010769:Phosphothreonine; D010768:Phosphoserine; D010447:Peptide Hydrolases