The adeno-associated virus (AAV) Rep proteins use a unique AAA+ domain to catalyze DNA replication, transcription regulation, and genome packaging. Also, they mediate site-specific integration during a latent phase. To understand the mechanisms underlying AAV Rep function, we investigated the cryo-EM and X-ray structures of Rep68-ssDNA complexes. Surprisingly, Rep68 generates hybrid ring structures where the Origin-Binding-Domain (OBD) forms octameric rings while the helicase domain (HD) forms heptamers. Moreover, the binding to ATPγS promotes a large conformational change in the entire AAA+ domain that leads the HD to form both heptamers and hexamers. The HD oligomerization is driven by an interdomain linker region that acts as a latch to catch the neighboring HD subunit and is flexible enough to permit the formation of different stoichiometric ring structures. Overall, our studies show the structural basis of AAV Rep structural flexibility required to fulfill its multifunctional role during the AAV life cycle.

中文翻译：

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与ssDNA结合的AAV2 Rep68的Cryo-EM结构揭示了可延展的AAA +机器，可以在低聚状态之间切换。

腺相关病毒（AAV）Rep蛋白使用独特的AAA +域来催化DNA复制，转录调控和基因组包装。此外，它们在潜在阶段中调解特定于站点的集成。为了了解AAV Rep功能的潜在机制，我们研究了Rep68-ssDNA复合物的冷冻EM和X射线结构。令人惊讶的是，Rep68产生杂化环结构，其中起源结合域（OBD）形成八聚体环，而解旋酶结构域（HD）形成七聚体。此外，与ATPγS的结合会促进整个AAA +域中的构象变化，从而导致HD形成七聚体和六聚体。HD低聚是由畴间连接区驱动的，该畴间连接区用作闩锁以捕获相邻的HD亚基，并且具有足够的柔韧性以允许形成不同的化学计量的环结构。总体而言，我们的研究表明AAV Rep在AAV生命周期中发挥其多功能作用所需的结构灵活性的结构基础。