CapRel

Contributors: Héloïse Georjon, Florian Tesson

Description

CapRel is a fused toxin-antitoxin system that is active against diverse phages when expressed in Escherichia coli () . CapRel belongs to the family of toxSAS toxin-antitoxin systems. CapRel is an Abortive infection system that is found in Cyanobacteria, Actinobacteria, Proteobacteria, Spirochetes, Bacteroidetes, and Firmicutes, as well as in some temperate phages.

Molecular mechanism

The CapRel system of Salmonella temperate phage SJ46 is normally found in a closed conformation, which is thought to maintain CapRel in an auto-inhibited state. However, during phage SECPhi27 infection, binding of the major phage capsid protein (Gp57) to CapRel releases it from is inhibited state, allowing pyrophosphorylation of tRNAs by the toxin domain and resulting in translation inhibition () . Other phage capsid proteins can be recognized by CapRel, as observed during infection by phage Bas8.

Different CapRel homologs confer defense against different phages, suggesting variable phage specificity of CapRel system which seems to be mediated by the C-terminal region of CapRel.

Example of genomic structure

The CapRel is composed of 1 protein: CapRel.

Here is an example found in the RefSeq database:

The CapRel system in Campylobacter sp. RM12175 (GCF_002139875.1, NZ_CP018793) is composed of 1 protein: CapRel (WP_086315994.1)

Distribution of the system among prokaryotes

Among the 22,803 complete genomes of RefSeq, the CapRel is detected in 398 genomes (1.75 %).

The system was detected in 217 different species.

Proportion of genome encoding the CapRel system for the 14 phyla with more than 50 genomes in the RefSeq database.

Structure

CapRel

Example 1

Experimental validation

      
graph LR;
    Zhang_2022[Zhang et al., 2022] --> Origin_0
    Origin_0[Salmonella phage SJ46 
WP_001749390.1] --> Expressed_0[Escherichia coli]
    Expressed_0[Escherichia coli] ----> T2 & T4 & T6 & RB69 & SECphi27
    Zhang_2022[Zhang et al., 2022] --> Origin_1
    Origin_1[Enterobacter chengduensis 
WP_001749390.1] --> Expressed_1[Escherichia coli]
    Expressed_1[Escherichia coli] ----> T7
    Zhang_2022[Zhang et al., 2022] --> Origin_2
    Origin_2[Klebsiella pneumoniae 
WP_0235711397.1] --> Expressed_2[Escherichia coli]
    Expressed_2[Escherichia coli] ----> SECphi18
    subgraph Title1[Reference]
        Zhang_2022
end
    subgraph Title2[System origin]
        Origin_0
        Origin_1
        Origin_2
end
    subgraph Title3[Expression species]
        Expressed_0
        Expressed_1
        Expressed_2
end
    subgraph Title4[Protects against]
        T2
        T4
        T6
        RB69
        SECphi27
        T7
        SECphi18
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

    

References

10.1038/s41586-022-05444-z
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