Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping
Structural basis of Cas3 inhibition by the bacteriophage protein AcrF3.
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The AcrF3 homodimer locks Cas3 in an ADP-bound state, blocks its helicase DNA-binding tunnel, and masks the surfaces Cascade uses to recruit it
"AcrF3 forms a homodimer that locks PaCas3 in an ADP-bound form, blocks the entrance of the DNA-binding tunnel in the helicase domain, and masks the linker region and C-terminal domain of PaCas3, thereby preventing recruitment by Cascade and inhibiting the type I-F CRISPR-Cas system."
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The complex solved is AcrF3 with Pseudomonas aeruginosa Cas3
"Here we report the crystal structure of the anti-CRISPR protein AcrF3 in complex with Pseudomonas aeruginosa Cas3 (PaCas3)."
A CRISPR evolutionary arms race: structural insights into viral anti-CRISPR/Cas responses.
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The AcrF3 dimer binds the HD, Linker and CTD domains of Cas3 and blocks DNA access
"our structural analysis of the Cas3-AcrF3 complex revealed that the AcrF3 dimer binds to HD, Linker and CTD domains of the Cas3 protein, therefore blocking the replaced non-complementary DNA access of Cas3"
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Blocking Cas3 recruitment also blocks primed spacer acquisition, so the host cannot update its CRISPR memory
"DNA degradation via inhibiting recruitment of Cas3 by Csy complex. In addition, inhibition of Cas3-guided DNA degradation also blocks primed spacer acquisition. In summary, the AcrF3 dimer overcomes the CRISPR system at both the crRNA interference and the primed acquisition stages."
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In type I-F systems the sequestered nuclease is a Cas2-Cas3 fusion protein
"In the type I-F CRISPR system, Cas2 and Cas3 are coded by one gene as a fused protein"
Multiple mechanisms for CRISPR-Cas inhibition by anti-CRISPR proteins.
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AcrF3 binds the Cas3 helicase-nuclease and prevents its recruitment to the DNA-bound surveillance complex
"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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Because target recognition is left intact, the inhibited system acts in vivo as a transcriptional repressor
"In vivo, this anti-CRISPR can convert the CRISPR-Cas system into a transcriptional repressor"
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The three inhibitors studied are sequence-diverse and mechanistically distinct, implying independent evolution
"The diverse sequences and mechanisms of action of these anti-CRISPR proteins imply an independent evolution"
Bacteriophage genes that inactivate the CRISPR/Cas bacterial immune system.
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Anti-CRISPR proteins act after the crRNA-Cas complex has formed, 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."