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首页> 外文期刊>Journal of Molecular Biology >UNWINDING OF CLOSED CIRCULAR DNA BY THE ESCHERICHIA COLI RUVA AND RUVB RECOMBINATION REPAIR PROTEINS
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UNWINDING OF CLOSED CIRCULAR DNA BY THE ESCHERICHIA COLI RUVA AND RUVB RECOMBINATION REPAIR PROTEINS

机译：大肠埃希氏菌和RUVB重组修复蛋白解开闭合的环状DNA。

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摘要

The RuvA and RuvB proteins of Escherichia coli promote the branch migration of Holliday junctions during genetic recombination and the recombinational repair of damaged DNA. Using a topological assay that measures the underwinding of covalently closed duplex DNA, we find that RuvA and RuvB promote the transient unwinding of relaxed or supercoiled DNA. Detection of unwinding by RuvAB requires the presence of Am and a non-hydrolysable ATP analogue (ATP gamma S), and was not observed in the presence of ATP or ATP gamma S alone. These results indicate that RuvAB catalyse the unwinding and rewinding of duplex DNA via an intermediate that can be stabilised by the presence a non-hydrolysable cofactor. At elevated concentrations of Mg2+ (12 to 30 mM), which are known to favour RuvB binding to DNA without the need for RuvA, RuvB protein alone promotes DNA unwinding. These results show that RuvB protein, an ATPase that forms hexameric ring structures that encircle the DNA, is directly responsible for the DNA unwinding activity exhibited by RuvAB. From these results, we propose that branch migration of Holliday junctions by RuvAB occurs by the passage of double-stranded DNA through the RuvAB complex, in a reaction coupled to transient DNA unwinding. [References: 40]
机译：大肠杆菌的RuvA和RuvB蛋白在基因重组和受损DNA的重组修复过程中促进霍利迪结的分支迁移。使用测量共价封闭的双链体DNA的下链的拓扑分析，我们发现RuvA和RuvB促进了松弛或超螺旋DNA的瞬时解链。通过RuvAB检测解链需要存在Am和不可水解的ATP类似物（ATP gamma S），而在仅存在ATP或ATP gamma S的情况下则没有观察到。这些结果表明，RuvAB通过可以通过存在不可水解的辅因子而稳定的中间体催化双链DNA的展开和重绕。在较高的Mg2 +浓度（12至30 mM）下，已知它有助于RuvB与DNA结合，而无需RuvA，单独的RuvB蛋白可促进DNA解旋。这些结果表明，RuvB蛋白（一种形成环绕DNA的六聚环结构的ATPase）直接负责RuvAB展示的DNA展开活性。从这些结果，我们提出RuvAB的霍利迪结的分支迁移是通过双链DNA穿过RuvAB复合物而发生的，该反应与瞬时DNA解旋偶联。 [参考：40]

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