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Mode of Action (MoA)
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binds to the DNA-binding groove of the type I DNA restriction/modification complex with higher affinity than DNA and blocks it. Triggers Paris defence.
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Evidence
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Wild-type bacteriophage T7 is not subject to restriction by the Escherichia coli B and K restriction systems, but T7 mutants that are susceptible to such restriction have been isolated. These mutants are all defective in gene 0.3 (ECO_0000016), which encodes the Ocr protein. Ocr deletion mutants are unable to plate on restricting hosts (ECO_0001038). Moreover, T7 Δ0.3 mutants were blocked by BREX, while wild-type T7 (with intact Ocr) overcame BREX-mediated restriction (ECO_0000016). Complementation with plasmid-encoded Ocr restored infectivity (ECO_0000017), and Ocr was shown to physically interact with the BrxX methyltransferase (x-ray crystallography evidence, ECO_0005670).
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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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Escherichia coli type I RM and type I BREX
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Relevant publication(s)
DOI
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10.1016/0022-2836(75)90083-2,
10.1016/s1097-2765(02)00435-5,
10.1093/nar/gkaa290,
10.1038/s41467-025-57006-2
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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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1S7Z
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Genome(s) encoding the protein
Protein Source
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Escherichia phage T7
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Defence system(s) inhibited by the protein
Defences
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RM,
BREX
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