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Mode of Action (MoA)
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binds to the REC3 domain of SpyCas9.
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Evidence
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AcrIIA28 was identified from a Streptococcus phage element and tested using a plasmid interference assay in E. coli. In this system, E. coli was engineered to express SpyCas9 or St3Cas9 and an sgRNA targeting a co-transformed plasmid carrying an antibiotic resistance gene. Cas9-mediated cleavage of this plasmid resulted in loss of resistance and prevented colony formation on selective media. Co-expression of AcrIIA28 reversed this Cas9-induced growth inhibition, indicating strong anti-CRISPR activity. In vitro DNA cleavage assays confirmed that AcrIIA28 prevented formation of the Cas9–DNA complex. EMSAs further demonstrated that AcrIIA28 blocks DNA binding by Cas9 (ECO_0001807), consistent with its function as a DNA binding inhibitor.
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MoA Category
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binds and inhibits host defence system
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Subtype(s) of the defence system(s) inhibited by the protein
Defence Subtype
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Streptococcus thermophilus and Streptococcus pyogenes type II-A CRISPR-Cas
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Relevant publication(s)
DOI
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10.1093/nar/gkac099
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Other components of the anti-defence system
Multicomponent System
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-
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Known structure in PDB
PDB ID
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8WRX
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Genome(s) encoding the protein
Protein Source
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Streptococcus phage Javan128
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Defence system(s) inhibited by the protein
Defences
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CRISPR-Cas
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