Bockus B J, Schaffhausen B
J Virol. 1987 Apr;61(4):1155-63. doi: 10.1128/JVI.61.4.1155-1163.1987.
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.
多瘤病毒大T抗原在丝氨酸和苏氨酸残基上均被磷酸化，其比例约为6比1。这种磷酸化可分解为一系列9个金黄色葡萄球菌V8磷酸肽。所有这些磷酸肽都存在于一个分子量为57,000的N端胰凝乳蛋白酶片段中。一个分子量为50,000的C端甲酸片段不含磷酸。因此，与猴病毒40大T抗原不同，多瘤病毒大T抗原没有明显的C端磷酸化。有限的V8和羟胺裂解表明，磷酸化可定位于分子的两个不同部分。相当一部分磷酸定位于分子183位残基之前的N端部分。在该区域内，V8肽4、8和9代表更靠近N端的磷酸化，而肽1、2和3包含更远离N端的磷酸化。这些磷酸化均与猴病毒40大T抗原的磷酸化不同。V8磷酸肽5和7更远离N端，在生物学实验中可与N端磷酸化区分开来。甲酸图谱分析表明，这种磷酸化即使不是全部，也大部分位于257至285位残基之间。
