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Title | Structural rearrangements allow nucleic acid discrimination by type I-D Cascade. |
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Journal, issue, pages | Nat Commun, Vol. 13, Issue 1, Page 2829, Year 2022 |
Publish date | May 20, 2022 |
Authors | Evan A Schwartz / Tess M McBride / Jack P K Bravo / Daniel Wrapp / Peter C Fineran / Robert D Fagerlund / David W Taylor / |
PubMed Abstract | CRISPR-Cas systems are adaptive immune systems that protect prokaryotes from foreign nucleic acids, such as bacteriophages. Two of the most prevalent CRISPR-Cas systems include type I and type III. ...CRISPR-Cas systems are adaptive immune systems that protect prokaryotes from foreign nucleic acids, such as bacteriophages. Two of the most prevalent CRISPR-Cas systems include type I and type III. Interestingly, the type I-D interference proteins contain characteristic features of both type I and type III systems. Here, we present the structures of type I-D Cascade bound to both a double-stranded (ds)DNA and a single-stranded (ss)RNA target at 2.9 and 3.1 Å, respectively. We show that type I-D Cascade is capable of specifically binding ssRNA and reveal how PAM recognition of dsDNA targets initiates long-range structural rearrangements that likely primes Cas10d for Cas3' binding and subsequent non-target strand DNA cleavage. These structures allow us to model how binding of the anti-CRISPR protein AcrID1 likely blocks target dsDNA binding via competitive inhibition of the DNA substrate engagement with the Cas10d active site. This work elucidates the unique mechanisms used by type I-D Cascade for discrimination of single-stranded and double stranded targets. Thus, our data supports a model for the hybrid nature of this complex with features of type III and type I systems. |
External links | Nat Commun / PubMed:35595728 / PubMed Central |
Methods | EM (single particle) |
Resolution | 2.9 - 3.1 Å |
Structure data | EMDB-24974, PDB-7sba: EMDB-24976, PDB-7sbb: |
Source |
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Keywords | DNA BINDING PROTEIN/DNA/RNA / CRISPR / Complex / Ribonucleoprotein complex / type I-D / type ID / type I / cyanobacteria / synechocystis / RNA binding protein / DNA binding protein / DNA BINDING PROTEIN-DNA-RNA complex / RNA BINDING PROTEIN/RNA / RNA BINDING PROTEIN-RNA complex |