The DNA dependence of the ATPase activity of human DNA topoisomerase IIα
The DNA dependence of the ATPase activity of human DNA topoisomerase IIα
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DOI：
10.1074/jbc.272.51.32696
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发表时间：
1997-12-19
影响因子：
4.8
通讯作者：
Maxwell, A
中科院分区：
文献类型：
--
作者：
Hammonds, TR;Maxwell, A
我们从HeLa细胞中纯化了人拓扑异构酶II α，并研究了其atp酶反应。atp酶活性受DNA刺激，表现出明显的Michaelis-Menten动力学。虽然人类拓扑异构酶II α的atp酶活性低于酿酒酵母，但它在十烷基化中更活跃，这意味着在这些条件下atp酶更有效地偶联到DNA链通道。使用质粒pBR322作为DNA辅因子，反应显示碱基对与酶二聚体比例为100-200:1的DNA过度刺激。当使用DNA片段作为辅因子时，反应需要类似100个碱基对的>来刺激活性，类似300个碱基对的片段表现为超刺激。这种行为可以合理地解释为，酶需要片段既可以结合DNA门，也可以结合atp操作的钳，以刺激atp酶反应。过度刺激是DNA酶饱和的结果。讨论了这些结果的机理意义。
We have purified human topoisomerase II alpha from HeLa cells and studied its ATPase reaction. The ATPase activity is stimulated by DNA and shows apparent Michaelis-Menten kinetics. Although the ATPase activity of human topoisomerase II alpha is lower than that of Saccharomyces cerevisiae, it is more active in decatenation, implying more efficient coupling of the ATPase to DNA strand passage under these conditions. Using plasmid pBR322 as the DNA cofactor, the reaction shows hyperstimulation by DNA at a base pair to enzyme dimer ratio of 100-200:1. When DNA fragments are used as the cofactor, the reaction requires >similar to 100 base pairs to stimulate the activity and fragments of similar to 300 base pairs show hyperstimulation. This behavior can be rationalized in terms of the enzyme requiring fragments that can bind to both the DNA gate and the ATP-operated clamp in order for the ATPase reaction to be stimulated. Hyperstimulation is a consequence of the saturation of DNA with enzyme. The mechanistic implications of these results are discussed.