9irg

Cryo-EM Structure of RNA

spinqualitylabelsall models 9irg, resolution 4.59Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 9irg is a 27 chain structure with sequence from Pectobacterium atrosepticum SCRI1043 and Thiocystis violascens. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: Electron Microscopy, Resolution 4.59Å Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function CSY3_PECAS CRISPR (clustered regularly interspaced short palindromic repeat) is an adaptive immune system that provides protection against mobile genetic elements (viruses, transposable elements and conjugative plasmids). CRISPR clusters contain sequences complementary to antecedent mobile elements and target invading nucleic acids. CRISPR clusters are transcribed and processed into CRISPR RNA (crRNA). Publication Abstract from PubMed RNA-based anti-CRISPRs (Racrs) interfere with the type I-F CRISPR-Cas system by mimicking the repeats found in CRISPR arrays. Here, we determined the cryo-electron microscopy (cryo-EM) structures of the type I-F crRNA-guided surveillance complex (Csy complex) from Pectobacterium atrosepticum and three RacrIF1-induced aberrant subcomplexes. Additionally, we observed that Cas7f proteins could bind to non-specific nucleic acids, forming right-handed superhelical filaments composed of different Cas7 copies. Mechanistically, RacrIF1 lacks the specific S-conformation observed in the corresponding position of the 5' handle in canonical CRISPR complexes, and it instead adopts a periodic "5 + 1" pattern. This conformation creates severe steric hindrance for Cas5f-Cas8f heterodimer and undermines their binding. Furthermore, Cas7f nonspecifically binds nucleic acids and can form infinite superhelical filaments along Racrs molecules. This oligomerization sequesters Cas6f and Cas7f from binding, therefore blocking the formation of functional CRISPR-Cas effector complexes and ultimately blocking antiviral immunity. Our study provides a structural basis underlying Racrs-mediated CRISPRs inhibition. RNA anti-CRISPRs deplete Cas proteins to inhibit the CRISPR-Cas system.,Gao X, Zhu K, Zhang W, Wang L, Wang L, Hua L, Niu T, Qin B, Yu X, Zhu H, Cui S Mol Cell. 2025 Dec 30:S1097-2765(25)00979-7. doi: 10.1016/j.molcel.2025.12.005. PMID:41475348 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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