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Mode of Action (MoA)
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may directly interact with the toxin, toxN. AlphaFold 3 predicts a direct interaction between ToxN (https://www.ncbi.nlm.nih.gov/protein/WP_012609144.1) and Tifa (ipTM = 0.72, pTM = 0.75).
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Evidence
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TifA was identified as a phage-encoded inhibitor of the bacterial toxin ToxN through experimental evolution of T4 phage on E. coli expressing the toxIN toxin-antitoxin system. Segmental amplification of the dmd-tifA locus was repeatedly selected in independently evolved T4 populations, enhancing infectivity on toxIN-containing hosts. Cloning and overexpression of tifA alone (but not dmd) in E. coli restored T4 infection in toxIN-expressing cells, confirming tifA as the active anti-defense factor. Functional assays showed that co-expression of TifA neutralized ToxN toxicity, rescuing cell growth. Deletion of the tifA start codon abolished this rescue, while a codon-recoded tifA retained activity, indicating that TifA acts as a protein antitoxin. Co-immunoprecipitation (ECO_0000085) experiments demonstrated a physical interaction between TifA and ToxN in vivo. Finally, T4 clones with tifA deletions lost the ability to infect cells with chromosomally encoded toxIN, confirming the necessity of TifA for defense evasion. These findings establish TifA as a direct, proteinaceous anti-toxin that inhibits ToxN-mediated phage defense. Binding it supported by computational structure modeling evidence (ECO_0006368).
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MoA Category
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binds and inhibits host defence system (putative)
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Subtype(s) of the defence system(s) inhibited by the protein
Defence Subtype
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Escherichia coli type III TA toxIN
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Relevant publication(s)
DOI
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10.7554/eLife.79549
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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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-
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Genome(s) encoding the protein
Protein Source
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Enterobacteria phage T4
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Defence system(s) inhibited by the protein
Defences
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TA
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