Auto-inhibition and activation of a short Argonaute-associated TIR-APAZ defense system
Auto-inhibition and activation of a short Argonaute-associated TIR-APAZ defense system
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DOI：
10.1038/s41589-023-01478-0
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发表时间：
2023-11-06
影响因子：
14.8
通讯作者：
Xiao，Yibei
中科院分区：
文献类型：
--
作者：
Guo，Lijie;Huang，Pingping;Xiao，Yibei
短原核Ago占大多数原核Argonaute蛋白（pAgos），并参与防御细菌入侵核酸。与TIR-APAZ（斯巴达）相关的短pAgo已显示在向导介导的靶DNA识别后寡聚化和耗尽NAD+。然而，斯巴达抑制和激活的分子基础仍然未知。在这项研究中，我们确定了Crenotalea thermophilaSPARTA在其抑制，瞬态和激活状态的低温电子显微镜结构。斯巴达单体被其酸性尾自身抑制，酸性尾占据导向-靶结合通道。向导介导的靶标结合排除该酸性尾并触发实质性构象变化以暴露Ago-Ago二聚化界面。因此，斯巴达组装成活性四聚体，其中四个TIR结构域重排并包装以形成NAD酶活性位点。结合生物化学证据，我们的研究结果提供了解释斯巴达自动抑制和激活的全景视图，并扩展了对pAgo介导的细菌防御系统的理解。
Short prokaryotic Ago accounts for most prokaryotic Argonaute proteins (pAgos) and is involved in defending bacteria against invading nucleic acids. Short pAgo associated with TIR-APAZ (SPARTA) has been shown to oligomerize and deplete NAD+upon guide-mediated target DNA recognition. However, the molecular basis of SPARTA inhibition and activation remains unknown. In this study, we determined the cryogenic electron microscopy structures ofCrenotalea thermophilaSPARTA in its inhibited, transient and activated states. The SPARTA monomer is auto-inhibited by its acidic tail, which occupies the guide-target binding channel. Guide-mediated target binding expels this acidic tail and triggers substantial conformational changes to expose the Ago–Ago dimerization interface. As a result, SPARTA assembles into an active tetramer, where the four TIR domains are rearranged and packed to form NADase active sites. Together with biochemical evidence, our results provide a panoramic vision explaining SPARTA auto-inhibition and activation and expand understanding of pAgo-mediated bacterial defense systems.