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Mode of Action (MoA)
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serves as a metal-independent phosphodiesterase and hydrolyses the host's cyclic di- and trinucleotide CBASS signals, such as 3'3'-cGAMP, 3'3'-cUA and 3'3'3'-cAAA.
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Evidence
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Cell lysates from E. coli infected with phage T4 degraded CBASS signals such as 3′3′-cGAMP, cUA, and cAAA. Purified T4 Acb1 protein selectively cleaved these CBASS cyclic dinucleotides and trinucleotides. A deletion mutant of T4 (Δacb1) failed to degrade 3′3′-cGAMP and showed over 300-fold reduced replication in CBASS-expressing E. coli compared to wild-type T4 (ECO_0001038). The crystal structure of Acb1 bound to 3′3′-cGAMP (ECO_0001034) revealed the mechanism of substrate recognition and metal-independent hydrolysis. In vitro, Acb1-treated 3′3′-cGAMP failed to activate CBASS effector proteins such as Cap5, confirming functional inhibition of immune signaling.
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MoA Category
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degrades or sequesters molecules utilised by host defence systems
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Subtype(s) of the defence system(s) inhibited by the protein
Defence Subtype
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Escherichia coli KTE188 type III CBASS
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Relevant publication(s)
DOI
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10.1038/s41586-022-04716-y
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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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7T26
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Genome(s) encoding the protein
Protein Source
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Escherichia phage T4
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Defence system(s) inhibited by the protein
Defences
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CBASS
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