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Title | Structural Basis for the Ribonuclease Activity of a Thermostable CRISPR-Cas13a from Thermoclostridium caenicola. |
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Journal, issue, pages | J Mol Biol, Vol. 435, Issue 17, Page 168197, Year 2023 |
Publish date | Sep 1, 2023 |
Authors | Feng Wang / Chendi Zhang / Haijiang Xu / Wanting Zeng / Lixin Ma / Zhuang Li / |
PubMed Abstract | 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 ...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 Å, and TccCas13a at 3.5 Å. 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. |
External links | J Mol Biol / PubMed:37442412 |
Methods | EM (single particle) |
Resolution | 2.9 - 3.5 Å |
Structure data | EMDB-28645, PDB-8ewg: EMDB-34484, PDB-8h4u: |
Source |
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Keywords | Hydrolase/RNA / riboendonuclease / RNA / Hydrolase-RNA complex |