Zhang Xu, Zhou Zixuan, Dai Lin, Chao Yulin, Liu Zheng, Huang Mingdong, Qu Qianhui, Lin Zhonghui
College of Chemistry, Fuzhou University, Fuzhou, China.
Shanghai Stomatological Hospital, Institutes of Biomedical Science, Department of Systems Biology for Medicine, Fudan University, Shanghai, China.
Front Plant Sci. 2023 Mar 21;14:1139106. doi: 10.3389/fpls.2023.1139106. eCollection 2023.
Holliday junction (HJ) is a four-way structured DNA intermediate in homologous recombination. In bacteria, the HJ-specific binding protein RuvA and the motor protein RuvB together form the RuvAB complex to catalyze HJ branch migration. (, Pa) is a ubiquitous opportunistic bacterial pathogen that can cause serious infection in a variety of host species, including vertebrate animals, insects and plants. Here, we describe the cryo-Electron Microscopy (cryo-EM) structure of the RuvAB-HJ intermediate complex from . The structure shows that two RuvA tetramers sandwich HJ at the junction center and disrupt base pairs at the branch points of RuvB-free HJ arms. Eight RuvB subunits are recruited by the RuvA octameric core and form two open-rings to encircle two opposite HJ arms. Each RuvB subunit individually binds a RuvA domain III. The four RuvB subunits within the ring display distinct subdomain conformations, and two of them engage the central DNA duplex at both strands with their C-terminal β-hairpins. Together with the biochemical analyses, our structure implicates a potential mechanism of RuvB motor assembly onto HJ DNA.
霍利迪连接体（HJ）是同源重组中一种四路结构的DNA中间体。在细菌中，HJ特异性结合蛋白RuvA和运动蛋白RuvB共同形成RuvAB复合物，以催化HJ分支迁移。（，Pa）是一种普遍存在的机会性细菌病原体，可在包括脊椎动物、昆虫和植物在内的多种宿主物种中引起严重感染。在这里，我们描述了来自的RuvAB-HJ中间复合物的冷冻电子显微镜（cryo-EM）结构。该结构表明，两个RuvA四聚体在连接中心夹住HJ，并破坏无RuvB的HJ臂分支点处的碱基对。八个RuvB亚基被RuvA八聚体核心招募，并形成两个开环以环绕两个相对的HJ臂。每个RuvB亚基单独结合一个RuvA结构域III。环内的四个RuvB亚基显示出不同的亚结构域构象，其中两个通过其C端β-发夹与中央DNA双链的两条链结合。结合生化分析，我们的结构暗示了RuvB运动蛋白组装到HJ DNA上的潜在机制。
