Ross C F, Brougham M J, Holloman W K, Ross W E
Biochim Biophys Acta. 1983 Nov 17;741(2):230-6. doi: 10.1016/0167-4781(83)90063-5.
A nuclear type I topoisomerase from mouse leukemia L1210 cells has been partially purified and characterized. The sedimentation coefficient of the enzyme by velocity sedimentation is 4.3 S, consistent with a globular protein of 68 kDa. Enzyme activity is stimulated 20-fold in the presence of magnesium over that achieved in KCl alone. The enzyme is completely inhibited in the presence of the berenil congeners HOE 13548 and 15030 while berenil itself caused only partial inhibition at concentrations below 200 micrograms/ml. An acid soluble protein of 30 kDa (by SDS-polyacrylamide gel electrophoresis) co-purified with the topoisomerase but could be separated by precipitation in a low salt buffer. This protein, as well as a protein of similar characteristics, histone H1, stimulated topoisomerase activity over a narrow concentration range. The role of topoisomerase in the DNA strand scission observed in L1210 cells following exposure to intercalating agents remains conjectural as the purified enzyme did not produce nicks in plasmid DNA in the presence of adriamycin.
从小鼠白血病L1210细胞中部分纯化并鉴定了一种核I型拓扑异构酶。通过速度沉降法测得该酶的沉降系数为4.3 S，与68 kDa的球状蛋白一致。在镁存在的情况下，酶活性比仅在氯化钾中时提高了20倍。在贝尼尔类似物HOE 13548和15030存在时，该酶被完全抑制，而贝尼尔本身在浓度低于200微克/毫升时仅引起部分抑制。一种30 kDa的酸溶性蛋白（通过SDS-聚丙烯酰胺凝胶电泳测定）与拓扑异构酶共纯化，但可通过在低盐缓冲液中沉淀分离。这种蛋白以及具有相似特性的组蛋白H1在狭窄的浓度范围内刺激拓扑异构酶活性。由于纯化的酶在阿霉素存在的情况下未在质粒DNA中产生切口，因此拓扑异构酶在L1210细胞暴露于嵌入剂后观察到的DNA链断裂中的作用仍不确定。
