SEFIR

Contributors: Helena Shomar, Marie Guillaume

Description

The SEFIR defense system is composed of a single bacterial SEFIR (bSEFIR)-domain protein. bSEFIR-domain genes were identified in bacterial genomes and were shown to be enriched in defense islands and the activity of the defense system was first experimentally validated in Bacillus sp. NIO-1130 against phage Phi29 () .

Bacterial SEFIR domains were named after their eukaryotic homologs which were already known to be part of several eukaryotic immune proteins (e.g. SEFs and Interleukin-17 Receptors):ref{doi=10.1016/S0968-0004(03)00067-7}.

Homologs of SEFIR domain proteins were also found in archaeal species: Methanosarcina barkeri and Methanosarcina mazei () .

Molecular mechanism

SEFIR was shown to protect against phage infection through an abortive infection mechanism via NAD+ depletion. This is similar to what can be observed in other defense systems containing a TIR domain that shares homology with the SEFIR domain (in eukaryotes, both domains are part of the STIR superfamily) () .

Example of genomic structure

The SEFIR is composed of 1 protein: bSEFIR.

Here is an example found in the RefSeq database:

The SEFIR system in Haliangium ochraceum (GCF_000024805.1, NC_013440) is composed of 1 protein: bSEFIR (WP_012827923.1)

Distribution of the system among prokaryotes

Among the 22,803 complete genomes of RefSeq, the SEFIR is detected in 358 genomes (1.57 %).

The system was detected in 218 different species.

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

Structure

SEFIR

Example 1

Experimental validation

      
graph LR;
    Millman_2022[Millman et al., 2022] --> Origin_0
    Origin_0[Bacillus sp. NIO-1130 
2616229772] --> Expressed_0[Bacillus subtilis]
    Expressed_0[Bacillus subtilis] ----> phi29
    subgraph Title1[Reference]
        Millman_2022
end
    subgraph Title2[System origin]
        Origin_0
end
    subgraph Title3[Expression species]
        Expressed_0
end
    subgraph Title4[Protects against]
        phi29
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

10.1016/j.chom.2022.09.017
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10.1016/S0968-0004(03)00067-7
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