Bebel Aleksandra, Karaca Ezgi, Kumar Banushree, Stark W Marshall, Barabas Orsolya
Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany.
Institute of Molecular, Cell and Systems Biology, University of Glasgow, Glasgow, United Kingdom.
Elife. 2016 Dec 23;5:e19706. doi: 10.7554/eLife.19706.
Bacterial Xer site-specific recombinases play an essential genome maintenance role by unlinking chromosome multimers, but their mechanism of action has remained structurally uncharacterized. Here, we present two high-resolution structures of XerH with its recombination site DNA , representing pre-cleavage and post-cleavage synaptic intermediates in the recombination pathway. The structures reveal that activation of DNA strand cleavage and rejoining involves large conformational changes and DNA bending, suggesting how interaction with the cell division protein FtsK may license recombination at the septum. Together with biochemical and in vivo analysis, our structures also reveal how a small sequence asymmetry in defines protein conformation in the synaptic complex and orchestrates the order of DNA strand exchanges. Our results provide insights into the catalytic mechanism of Xer recombination and a model for regulation of recombination activity during cell division.
细菌Xer位点特异性重组酶通过解开染色体多聚体在基因组维持中发挥重要作用，但其作用机制在结构上仍未得到表征。在这里，我们展示了XerH与其重组位点DNA的两个高分辨率结构，代表了重组途径中的切割前和切割后突触中间体。这些结构表明，DNA链切割和重新连接的激活涉及大的构象变化和DNA弯曲，这表明与细胞分裂蛋白FtsK的相互作用可能如何在隔膜处许可重组。结合生化和体内分析，我们的结构还揭示了 中的一个小序列不对称如何定义突触复合物中的蛋白质构象并协调DNA链交换的顺序。我们的结果为Xer重组的催化机制提供了见解，并为细胞分裂过程中重组活性的调节提供了一个模型。
