8h4u

Cryo-EM structure of a riboendonuclease

spinqualitylabelsall models 8h4u, resolution 3.50Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 8h4u is a 1 chain structure with sequence from Thermoclostridium caenicola. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: Electron Microscopy, Resolution 3.5Å Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function A0A1M6GDI0_9FIRM Publication Abstract from PubMed The RNA-targeting type VI CRISPR-Cas effector complexes are widely used in biotechnology applications such as gene knockdown, RNA editing, and molecular diagnostics. Compared with Cas13a from mesophilic organisms, a newly discovered Cas13a from thermophilic bacteria Thermoclostridium caenicola (TccCas13a) shows low sequence similarity, high thermostability, and lacks pre-crRNA processing activity. The thermostability of TccCas13a has been harnessed to make a sensitive and robust tool for nucleic acid detection. Here we present the structures of TccCas13a-crRNA binary complex at 2.8 A, and TccCas13a at 3.5 A. Although TccCas13a shares a similarly bilobed architecture with other mesophilic organism-derived Cas13a proteins, TccCas13a displayed distinct structure features. Specifically, it holds a long crRNA 5'-flank, forming extensive polar contacts with Helical-1 and HEPN2 domains. The detailed analysis of the interaction between crRNA 5'-flank and TccCas13a suggested lack of suitable nucleophile to attack the 2'-OH of crRNA 5'-flank may explain why TccCas13a fails to cleave pre-crRNA. The stem-loop segment of crRNA spacer toggles between double-stranded and single-stranded conformational states, suggesting a potential safeguard mechanism for target recognition. Superimposition of the structures of TccCas13a and TccCas13a-crRNA revealed several conformational changes required for crRNA loading, including dramatic movement of Helical-2 domain. Collectively, these structural insights expand our understanding into type VI CRISPR-Cas effectors, and would facilitate the development of TccCas13a-based applications. Structural Basis for the Ribonuclease Activity of a Thermostable CRISPR-Cas13a from Thermoclostridium caenicola.,Wang F, Zhang C, Xu H, Zeng W, Ma L, Li Z J Mol Biol. 2023 Sep 1;435(17):168197. doi: 10.1016/j.jmb.2023.168197. Epub 2023 , Jul 11. PMID:37442412 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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