Structure Reveals a Mechanism of CRISPR-RNA-Guided Nuclease Recruitment and Anti-CRISPR Viral Mimicry
- Rollins, MaryClare F. [ Montana State University: Microbiology & Cell Biology ]
- Chowdhury, Saikat [ Department of Integrative Structural and Computational Biology, Scripps Research Institute, La Jolla, CA ]
- Carter, Joshua [ Montana State University: Microbiology & Cell Biology ]
- Golden, Sarah M. [ Montana State University: Microbiology & Cell Biology ]
- Miettinen, Heini M. [ Montana State University: Microbiology & Cell Biology ]
- Santiago-Frangos, Andrew [ Montana State University: Microbiology & Cell Biology ]
- Faith, Dominick [ Montana State University: Microbiology & Cell Biology ]
- Lawrence, C. Martin [ Montana State University: Chemistry & Biochemistry ]
- Lander, Gabriel C. [ Department of Integrative Structural and Computational Biology, Scripps Research Institute, La Jolla, CA ]
- Wiedenheft, Blake A. [ Montana State University: Microbiology & Cell Biology ]
Bacteria and archaea have evolved sophisticated adaptive immune systems that rely on CRISPR RNA (crRNA)-guided detection and nuclease-mediated elimination of invading nucleic acids. Here, we present the cryo-electron microscopy (cryo-EM) structure of the type I-F crRNA-guided surveillance complex (Csy complex) from Pseudomonas aeruginosa bound to a double-stranded DNA target. Comparison of this structure to previously determined structures of this complex reveals a ∼180-degree rotation of the C-terminal helical bundle on the “large†Cas8f subunit. We show that the double-stranded DNA (dsDNA)-induced conformational change in Cas8f exposes a Cas2/3 “nuclease recruitment helix†that is structurally homologous to a virally encoded anti-CRISPR protein (AcrIF3). Structural homology between Cas8f and AcrIF3 suggests that AcrIF3 is a mimic of the Cas8f nuclease recruitment helix.