Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea.
J Am Chem Soc. 2011 Feb 2;133(4):668-71. doi: 10.1021/ja107498y.
Z-DNA, a left-handed isoform of Watson and Crick’s B-DNA, is rarely formed without the help of high salt concentrations or negative supercoiling. However, Z-DNA-binding proteins can efficiently convert specific sequences of the B conformation into the Z conformation in relaxed DNA under physiological salt conditions. As in the case of many other specific interactions coupled with structural rearrangements in biology, it has been an intriguing question whether the proteins actively induce Z-DNAs or passively trap transiently preformed Z-DNAs. In this study, we used single-molecule fluorescence assays to observe intrinsic B-to-Z transitions, protein association/dissociation events, and accompanying B-to-Z transitions. The results reveal that intrinsic Z-DNAs are dynamically formed and effectively stabilized by Z-DNA-binding proteins through efficient trapping of the Z conformation rather than being actively induced by them. Our study provides, for the first time, detailed pictures of the intrinsic B-to-Z transition dynamics and protein-induced B-to-Z conversion mechanism at the single-molecule level.
Z-DNA，沃森和克里克的 B-DNA 的左手异构体，在没有高盐浓度或负超螺旋帮助的情况下很少形成。然而，Z-DNA 结合蛋白可以在生理盐条件下将 B 构象的特定序列有效地转化为 Z 构象。与生物学中许多其他与结构重排偶联的特定相互作用一样，一个有趣的问题是蛋白质是主动诱导 Z-DNA 还是被动捕获瞬时形成的 Z-DNA。在这项研究中，我们使用单分子荧光分析来观察内在的 B 到 Z 转变、蛋白的结合/解离事件以及伴随的 B 到 Z 转变。结果表明，内在的 Z-DNA 是通过有效地捕获 Z 构象而动态形成并被 Z-DNA 结合蛋白有效稳定的，而不是被它们主动诱导形成的。我们的研究首次在单分子水平上提供了内在的 B 到 Z 转变动力学和蛋白诱导的 B 到 Z 转换机制的详细图片。
