Vologodskii A V, Zhang W, Rybenkov V V, Podtelezhnikov A A, Subramanian D, Griffith J D, Cozzarelli N R
Department of Chemistry, New York University, Washington Square, New York, NY 10003, USA.
Proc Natl Acad Sci U S A. 2001 Mar 13;98(6):3045-9. doi: 10.1073/pnas.061029098.
Type II DNA topoisomerases actively reduce the fractions of knotted and catenated circular DNA below thermodynamic equilibrium values. To explain this surprising finding, we designed a model in which topoisomerases introduce a sharp bend in DNA. Because the enzymes have a specific orientation relative to the bend, they act like Maxwell's demon, providing unidirectional strand passage. Quantitative analysis of the model by computer simulations proved that it can explain much of the experimental data. The required sharp DNA bend was demonstrated by a greatly increased cyclization of short DNA fragments from topoisomerase binding and by direct visualization with electron microscopy.
II型DNA拓扑异构酶能积极地将打结和连环的环状DNA的比例降低到热力学平衡值以下。为了解释这一惊人发现，我们设计了一个模型，其中拓扑异构酶在DNA中引入一个急剧弯曲。由于这些酶相对于弯曲具有特定的方向，它们就像麦克斯韦妖一样，提供单向链通过。通过计算机模拟对该模型进行定量分析，证明它可以解释许多实验数据。从拓扑异构酶结合的短DNA片段的环化大大增加以及通过电子显微镜直接观察，证明了所需的急剧DNA弯曲。
