Department of Agricultural Biotechnology, Seoul National University, Seoul 08826, Korea.
Bio-Chemical Analysis Team, Korea Basic Science Institute, Ochang 28119, Korea.
Nucleic Acids Res. 2022 Feb 28;50(4):2363-2376. doi: 10.1093/nar/gkac096.
Bacteria and archaea use the CRISPR-Cas system to fend off invasions of bacteriophages and foreign plasmids. In response, bacteriophages encode anti-CRISPR (Acr) proteins that potently inhibit host Cas proteins to suppress CRISPR-mediated immunity. AcrIE4-F7, which was isolated from Pseudomonas citronellolis, is a fused form of AcrIE4 and AcrIF7 that inhibits both type I-E and type I-F CRISPR-Cas systems. Here, we determined the structure of AcrIE4-F7 and identified its Cas target proteins. The N-terminal AcrIE4 domain adopts a novel α-helical fold that targets the PAM interaction site of the type I-E Cas8e subunit. The C-terminal AcrIF7 domain exhibits an αβ fold like native AcrIF7, which disables target DNA recognition by the PAM interaction site in the type I-F Cas8f subunit. The two Acr domains are connected by a flexible linker that allows prompt docking onto their cognate Cas8 targets. Conserved negative charges in each Acr domain are required for interaction with their Cas8 targets. Our results illustrate a common mechanism by which AcrIE4-F7 inhibits divergent CRISPR-Cas types.
细菌和古菌利用 CRISPR-Cas 系统抵御噬菌体和外来质粒的入侵。作为回应，噬菌体编码抗 CRISPR（Acr）蛋白，这些蛋白能够强烈抑制宿主 Cas 蛋白，从而抑制 CRISPR 介导的免疫。从香茅假单胞菌中分离到的 AcrIE4-F7 是 AcrIE4 和 AcrIF7 的融合形式，它可以抑制 I 型-E 和 I 型-F CRISPR-Cas 系统。在这里，我们确定了 AcrIE4-F7 的结构，并鉴定了其 Cas 靶蛋白。N 端 AcrIE4 结构域采用了一种新的α-螺旋折叠，靶向 I 型-E Cas8e 亚基的 PAM 相互作用位点。C 端 AcrIF7 结构域表现出类似于天然 AcrIF7 的 αβ 折叠，该折叠使 Cas8f 亚基的 PAM 相互作用位点无法识别靶 DNA。两个 Acr 结构域通过一个柔性接头连接，允许它们快速对接其同源 Cas8 靶标。每个 Acr 结构域中的保守负电荷对于与它们的 Cas8 靶标相互作用是必需的。我们的结果说明了 AcrIE4-F7 抑制不同的 CRISPR-Cas 类型的共同机制。
Zotero 插件
