Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping
Bacteriophage genes that inactivate the CRISPR/Cas bacterial immune system.
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First identification of phage genes that inactivate a host CRISPR-Cas system
"Here we describe the first examples of genes that mediate the inhibition of a CRISPR/Cas system. Five distinct 'anti-CRISPR' genes were found in the genomes of bacteriophages infecting Pseudomonas aeruginosa."
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Expressing an anti-CRISPR gene is sufficient to rescue plaquing of CRISPR-sensitive phages
"Remarkably, expression of seven of these genes (Supplementary Fig. 7) led to dramatic increases in the plaquing efficiency of the CRISPR-sensitive phages"
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Inhibition acts after the crRNA-Cas complex has assembled, not on crRNA or Cas protein biogenesis
"We conclude from these experiments that the anti-CRISPR genes exert their effects at a step occurring after formation of the crRNA-Cas complex, and that there is no effect on biogenesis of either the crRNA or Cas proteins."
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Specificity is restricted to type I-F and does not extend to the closely related type I-E
"Finally, we found that the anti-CRISPR genes did not inhibit a Type I-E CRISPR/Cas system functioning in E. coli"
Structure Reveals Mechanisms of Viral Suppressors that Intercept a CRISPR RNA-Guided Surveillance Complex.
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AcrF2 is a DNA mimic
"AcrF2 is a DNA mimic"
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AcrF2 occupies the lysine-rich DNA-capture pocket between Cas8f and Cas7f
"AcrF2 is a small acidic protein wedged between positively charged residues in the N-terminal hook of Cas8 and the thumb of Cas7.6f"
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The acidic surface residues are arranged pseudo-helically so as to reproduce the charge spacing of a DNA duplex backbone
"we did noticed a pseudo-helical display of acidic residues on the surface of AcrF2 mimics the negative charge distribution on the helical backbone of a DNA duplex"
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Inhibition is competitive occupancy of the DNA-binding site, supported by interface mutations that abolish both AcrF2 and DNA binding
"these results suggest that AcrF2 is a double-stranded DNA mimic that blocks target recognition by competing for a critical DNA binding site"
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AcrF2 blocks target recognition by inserting between the tail subunits Cas8f and Cas7f
"by inserting between the Cas8f and Cas7f subunits in the tail (AcrF2), which prevents interactions with the t"
Cryo-EM Structures Reveal Mechanism and Inhibition of DNA Targeting by a CRISPR-Cas Surveillance Complex.
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AcrF2 binding drives the Cas8f hook domain away from the closed, DNA-bound conformation
"AcrF2 binding wrenches the hook outwards away from the closed state"
Multiple mechanisms for CRISPR-Cas inhibition by anti-CRISPR proteins.
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Two of the three inhibitors studied block the DNA-binding activity of the surveillance complex, by contacting different subunits
"Two block the DNA-binding activity of the CRISPR-Cas complex, yet do this by interacting with different protein subunits, and using steric or non-steric modes of inhibition."
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The third inhibitor acts on the nuclease rather than the surveillance complex, which is the basis for separating the two mechanism classes
"The third anti-CRISPR protein operates by binding to the Cas3 helicase-nuclease and preventing its recruitment to the DNA-bound CRISPR-Cas complex."
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Sequence and mechanistic diversity imply independent evolution of the inhibitors
"The diverse sequences and mechanisms of action of these anti-CRISPR proteins imply an independent evolution"
Inhibition Mechanism of an Anti-CRISPR Suppressor AcrIIA4 Targeting SpyCas9.
Solution structure and dynamics of anti-CRISPR AcrIIA4, the Cas9 inhibitor.
Structural snapshots of R-loop formation by a type I-C CRISPR Cascade.