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Mode of Action (MoA)
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binds to RecA protein.
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Evidence
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In a recA441 strain, which constitutively activates the SOS response, overexpression of PsiB from plasmid R6-5 or from an engineered F plasmid with a Tn10 promoter prevented LexA cleavage and SOS induction (as measured by sfiA expression). This demonstrated that PsiB directly inhibits RecA’s coprotease activity even without exogenous DNA damage. Immunoquantification showed that ~1500 PsiB tetramers per cell were sufficient to suppress RecA coprotease activity, even in cells with ~100,000 RecA monomers. However, suppression of UV-induced SOS required higher PsiB levels (~40,000 tetramers), indicating that PsiB targets a subset of RecA molecules—likely those bound to transient ssDNA during replication.
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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 SOS response
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Relevant publication(s)
DOI
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10.1111/j.1365-2958.1992.tb01539.x,
10.1016/j.molcel.2009.07.026
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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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3NCT_A
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Genome(s) encoding the protein
Protein Source
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Escherichia coli plasmid
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Defence system(s) inhibited by the protein
Defences
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SOS stress response
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