PT  - JOURNAL ARTICLE
AU  - MaryClare F. Rollins
AU  - Saikat Chowdhury
AU  - Joshua Carter
AU  - Sarah M. Golden
AU  - Heini M. Miettinen
AU  - Andrew Santiago-Frangos
AU  - Dominick Faith
AU  - C. Martin Lawrence
AU  - Gabriel C. Lander
AU  - Blake Wiedenheft
TI  - Structure reveals mechanism of CRISPR RNA-guided nuclease recruitment and anti-CRISPR viral mimicry
AID  - 10.1101/453720
DP  - 2018 Jan 01
TA  - bioRxiv
PG  - 453720
4099  - http://biorxiv.org/content/early/2018/10/26/453720.short
4100  - http://biorxiv.org/content/early/2018/10/26/453720.full
AB  - 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-EM structure of the type I-F CRISPR RNA-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 Ȉ180-degree rotation of the C-terminal helical bundle on the “large” Cas8f subunit. We show that the 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”, implying that cas genes may sometimes serve as genetic fodder for the evolution of anti-CRISPRs.