Sekimizu K, Kubo Y, Segawa K, Natori S
Biochemistry. 1981 Apr 14;20(8):2286-92. doi: 10.1021/bi00511a033.
The structures of two protein factors, S-II and S-II', that specifically stimulate RNA polymerase II from Ehrlich ascites tumor cells were compared. The two proteins behaved differently on CM-cellulose chromatography and on isoelectric focusing, although they were shown to have common antigenicity. The following findings strongly suggest that S-II and S-II' have the same primary structure, but that S-II' is more extensively phosphorylated than S-II: (1)S-II an S-II' gave identical peptide maps when digested with various proteases. (2) S-II' that had been treated with alkaline phosphatases had the same mobility on sodium dodecyl sulfate-polyacrylamide gel as S-II, indicating that it could be converted to S-II by hydrolysis of its phosphate residues. (3) S-II' was phosphorylated more than S-II when Ehrlich ascites tumor cells were labeled in vivo with [32P]orthophosphate.
对两种能特异性刺激艾氏腹水瘤细胞RNA聚合酶II的蛋白质因子S-II和S-II'的结构进行了比较。这两种蛋白质在CM-纤维素色谱和等电聚焦上表现不同，尽管它们显示出共同的抗原性。以下发现强烈表明S-II和S-II'具有相同的一级结构，但S-II'比S-II磷酸化程度更高：(1)用各种蛋白酶消化时，S-II和S-II'给出相同的肽图。(2)用碱性磷酸酶处理过的S-II'在十二烷基硫酸钠-聚丙烯酰胺凝胶上的迁移率与S-II相同，表明通过水解其磷酸残基可将其转化为S-II。(3)当用[32P]正磷酸盐在体内标记艾氏腹水瘤细胞时，S-II'比S-II磷酸化程度更高。
