Dröge P
Department of Biology, University of Konstanz, Germany.
Nucleic Acids Res. 1992 Dec 11;20(23):6159-66. doi: 10.1093/nar/20.23.6159.
Fast and efficient recombination catalyzed by gamma delta resolvase in vitro requires negative DNA supercoiling of plasmid substrates. The current model for recombination suggests that supercoiling is required to drive DNA strand exchange within a synaptic complex by 'simple rotation' of DNA-linked resolvase promoters. Surprisingly, DNA knots are recombined efficiently in the absence of supercoiling, whereby the rate of recombination increases with the number of irreducible DNA segment crossings, or nodes, within each substrate knot. Recombination products contain three knot nodes less than substrates, suggesting that a reduction in writhe drives the reaction. However, the proposed protomer rotation model predicts that writhe is not altered during the process of strand transfer but, instead, is reduced only when a synaptic complex disassembles after strand exchange. I present evidence that recombination of knotted and of linear substrates coincides with a disassembly of synaptic complexes. The results lead to a variant model for strand exchange on non-supercoiled substrates in which a specific disassembly of the synaptic complex, triggered by a reduction in writhe, guides the cleaved DNA into the recombinant configuration.
γδ 解离酶在体外催化的快速高效重组需要质粒底物的负 DNA 超螺旋。当前的重组模型表明，超螺旋是通过与 DNA 相连的解离酶启动子的“简单旋转”来驱动突触复合物内的 DNA 链交换所必需的。令人惊讶的是，在没有超螺旋的情况下，DNA 结能高效重组，由此重组速率随着每个底物结内不可约 DNA 片段交叉数或节点数的增加而提高。重组产物比底物少三个结节点，这表明扭曲的减少驱动了反应。然而，所提出的原体旋转模型预测，在链转移过程中扭曲不会改变，而是仅在链交换后突触复合物解体时才会减少。我提供的证据表明，打结底物和线性底物的重组与突触复合物的解体同时发生。这些结果导致了一个关于非超螺旋底物上链交换的变体模型，其中由扭曲减少引发的突触复合物的特定解体将切割的 DNA 引导到重组构型中。
