Chang Yu-Wei, Ko Tzu-Ping, Lee Chien-Der, Chang Yuan-Chih, Lin Kuei-Ann, Chang Chia-Seng, Wang Andrew H-J, Wang Ting-Fang
Institute of Biochemical Science, National Taiwan University, Taipei, Taiwan.
PLoS One. 2009;4(3):e4890. doi: 10.1371/journal.pone.0004890. Epub 2009 Mar 19.
RecA family proteins, including bacterial RecA, archaeal RadA, and eukaryotic Dmc1 and Rad51, mediate homologous recombination, a reaction essential for maintaining genome integrity. In the presence of ATP, these proteins bind a single-strand DNA to form a right-handed nucleoprotein filament, which catalyzes pairing and strand exchange with a homologous double-stranded DNA (dsDNA), by as-yet unknown mechanisms. We recently reported a structure of RadA left-handed helical filament, and here present three new structures of RadA left-handed helical filaments. Comparative structural analysis between different RadA/Rad51 helical filaments reveals that the N-terminal domain (NTD) of RadA/Rad51, implicated in dsDNA binding, is highly flexible. We identify a hinge region between NTD and polymerization motif as responsible for rigid body movement of NTD. Mutant analysis further confirms that structural flexibility of NTD is essential for RadA's recombinase activity. These results support our previous hypothesis that ATP-dependent axial rotation of RadA nucleoprotein helical filament promotes homologous recombination.
RecA家族蛋白，包括细菌RecA、古菌RadA以及真核生物Dmc1和Rad51，介导同源重组，这是一种对维持基因组完整性至关重要的反应。在ATP存在的情况下，这些蛋白结合单链DNA形成右手核蛋白丝，该核蛋白丝通过尚未明确的机制催化与同源双链DNA（dsDNA）的配对和链交换。我们最近报道了RadA左手螺旋丝的结构，在此展示了RadA左手螺旋丝的三个新结构。不同RadA/Rad51螺旋丝之间的比较结构分析表明，与dsDNA结合有关的RadA/Rad51的N端结构域（NTD）具有高度灵活性。我们确定NTD和聚合基序之间的一个铰链区域是NTD刚体运动的原因。突变分析进一步证实，NTD的结构灵活性对RadA的重组酶活性至关重要。这些结果支持了我们之前的假设，即RadA核蛋白螺旋丝的ATP依赖性轴向旋转促进同源重组。
