DNA拓扑异构酶Ⅱ的多态转换模型

A Multi-States Model for DNA Topoisomerase Ⅱ Cycle

DNA拓扑异构酶Ⅱ是一种分子马达,它利用ATP水解产生的化学能,切断一条双链DNA片段(G segment),并让另一条双链DNA片段(T segment)从缺口处通过。对DNA拓扑异构酶Ⅱ的工作循环研究将有助于阐明其工作机理。本文根据已有实验资料,利用主方程方法构建了DNA拓扑异构酶Ⅱ状态转变的随机跃迁模型,求得系统各态的稳态解。进而推导出稳态下无机磷(Pi)浓度随时间的变化,得到DNA拓扑异构酶Ⅱ的最小工作周期约为0.78秒,该结果同实验获得的DNA拓扑异构酶Ⅱ工作周期为0.5～1秒一致。该模型定量地分析了DNA拓扑异构酶Ⅱ的动力学行为。

DNA topoisomerase Ⅱ is a molecular motor that couples ATP hydrolysis to the transport of one DNA segment（T segment） through a transient break in another segment（G segment）.The study of DNA topoisomerase Ⅱ cycle is useful in elucidating the mechanism of DNA topoisomerase Ⅱ work.Based onexperiments,a master equation approach is used to model multi-states change of DNA to poisomerase Ⅱcycle.The non-equilibrium steady state solution describes the probability distribution of each state as afunction of concentration of ATP.Moreover,the concentration of in organic phosphate Pi as a function oftime t and ATP concentration under steady state is obtained.By calculating the released velocity of Pi,wededuce that the minimized cycle of DNA topoisomerase Ⅱ is 0.78 second.This result is consistent with thecycle of DNA topoisomerase Ⅱ derived from experiments,which are in the range of 0.5～1 second.The conclusions demonstrate that the proposed model can qualitatively explain experiment results rather beingsatis factory.