Laboratoire de Physique de la Matière Vivante, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
FEBS Lett. 2011 Oct 3;585(19):3139-45. doi: 10.1016/j.febslet.2011.08.051. Epub 2011 Sep 6.
Type II topoisomerases (Topo II) are unique enzymes that change the DNA topology by catalyzing the passage of two double-strands across each other by using the energy from ATP hydrolysis. In vitro, human Topo II relaxes positive supercoiled DNA around 10-fold faster than negative supercoiled DNA. By using atomic force microscopy (AFM) we found that human Topo II binds preferentially to DNA cross-overs. Around 50% of the DNA crossings, where Topo II was bound to, presented an angle in the range of 80-90°, suggesting a favored binding geometry in the chiral discrimination by Topo II. Our studies with AFM also helped us visualize the dynamics of the unknotting action of Topo II in knotted molecules.
II 型拓扑异构酶（Topo II）是一种独特的酶，通过利用 ATP 水解产生的能量，催化两条双链彼此穿过，从而改变 DNA 的拓扑结构。在体外，人 Topo II 使正超螺旋 DNA 的松弛速度比负超螺旋 DNA 快约 10 倍。通过原子力显微镜（AFM），我们发现人 Topo II 优先结合 DNA 交叉。大约 50%的 Topo II 结合的 DNA 交叉呈现 80-90°的角度范围，表明 Topo II 在手性识别中存在有利的结合几何形状。我们使用 AFM 的研究还帮助我们可视化 Topo II 在扭结分子中解开扭结的动力学。
