DarTG

Contributors: Ernest Mordret

Description

The DarTG defense system is a toxin-antitoxin (TA) system that provides defense against bacteriophages by ADP-ribosylating viral DNA, thereby preventing replication and the production of mature virions. This system consists of two subfamilies, DarTG1 and DarTG2, which protect against different phages. When infected by specific phages, the DarT toxin, a DNA ADP-ribosyltransferase, is released, modifying viral DNA and inhibiting replication.

Molecular mechanism

DarT uses NAD+ to ADP-ribosylates thymidine on ssDNA, while DarG catalyzes the reverse reaction. ADP-ribosylation of ssDNA prevents DNA replication and triggers the cell's SOS response. While initially proposed to work on bacterial ssDNA as a TA system (N/A) , Leroux et al. (N/A) show that it mostly modifies viral DNA and therefore blocks viral replication and perturb the transcription of phage genes. They conclude that "DarTG does not ultimately kill the host cell as in a conventional Abi mechanism, but instead acts to thwart phage replication directly."

Example of genomic structure

The DarTG is composed of 2 proteins: DarT and DarG.

Here is an example found in the RefSeq database:

The DarTG system in Leptodesmis sichuanensis (GCF_021379005.1, NZ_CP075171) is composed of 2 proteins DarT (WP_233744308.1) DarG (WP_233744309.1)

Distribution of the system among prokaryotes

Among the NaN complete genomes of RefSeq, the DarTG is detected in NaN genomes (NaN %). The system was detected in NaN different species.
phylum
Percent genome having the system
0
100
Minimum genomes count to display

Structure

Summary
Group
Structure
System
Gene name
Subtype
Proteins in structure
System genes
Prediction type
N genes in sys
pLDDT
iptm+ptm
pDockQ
No data available

Experimental validation

      
graph LR;
    Leroux_2022[LeRoux et al., 2022] --> Origin_0
    Origin_0[Escherichia coli strain C7] --> Expressed_0[Escherichia coli]
    Expressed_0[Escherichia coli] ----> RB69 & T5 & SECphi18 & Lust
    subgraph Title1[Reference]
        Leroux_2022
end
    subgraph Title2[System origin]
        Origin_0
end
    subgraph Title3[Expression species]
        Expressed_0
end
    subgraph Title4[Protects against]
        RB69
        T5
        SECphi18
        Lust
end
    style Title1 fill:none,stroke:none,stroke-width:none
    style Title2 fill:none,stroke:none,stroke-width:none
    style Title3 fill:none,stroke:none,stroke-width:none
    style Title4 fill:none,stroke:none,stroke-width:none

    
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