Mokosh

Contributors: Marian Dominguez-Mirazo

Description

The Mokosh system was discovered in E. coli by examining clusters of genes enriched in defense islands () . It contains genes with an RNA helicase domain and a predicted phospholipase D domain (PLD) nuclease domain. Mutations in the ATP-binding domain of the helicase, and the active site of the PLD nuclease disrupt phage defense. The system is divided into two types. Mokosh type I has two genes, one gene containing the RNA helicase domain and an additional serine-threonine kinase domain (STK), and one gene containing the PLD nuclease. Type II Mokosh is formed of a single gene containing both the helicase and nuclease domains. Recent efforts have shown homology between the Mokosh system and human proteins involved in the piRNA pathway, a defense mechanism of animal germlines that prevents expression of transposable elements () . The system gets its name from the goddess protector of women's destiny in Slavic mythology () .

Molecular mechanisms

As far as we are aware, the molecular mechanism is unknown.

Example of genomic structure

A total of 7 subsystems have been described for the Mokosh system.

Here is some examples found in the RefSeq database:

The Mokosh_TypeII system in Massilia sp. NP310 (GCF_019443485.1, NZ_CP080379) is composed of 1 protein: MkoC (WP_184237977.1)

The Mokosh_Type_I_A system in Cupriavidus pauculus (GCF_019931045.1, NZ_CP082863) is composed of 2 proteins MkoA_A (WP_170292610.1) MkoB_A (WP_150981546.1)

The Mokosh_Type_I_B system in Collimonas pratensis (GCF_001584185.1, NZ_CP013234) is composed of 2 proteins MkoB_B (WP_061945389.1) MkoA_B (WP_061945390.1)

The Mokosh_Type_I_C system in Klebsiella sp. WP7-S18-CRE-02 (GCF_014169515.1, NZ_AP022189) is composed of 2 proteins MkoB_C (WP_227674162.1) MkoA_C (WP_227674163.1)

The Mokosh_Type_I_D system in Geomonas paludis (GCF_023221575.1, NZ_CP096574) is composed of 2 proteins MkoA_D (WP_248647094.1) MkoB_D (WP_248647095.1)

The Mokosh_Type_I_E system in Planococcus faecalis (GCF_002009235.1, NZ_CP019401) is composed of 2 proteins MkoA_E (WP_078080177.1) MkoB_E (WP_071154541.1)

Distribution of the system among prokaryotes

Among the 22,803 complete genomes of RefSeq, the Mokosh is detected in 1607 genomes (7.05 %).

The system was detected in 577 different species.

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

Structure

Mokosh_TypeI

Example 1
Example 2

Mokosh_TypeII

Example 1

Experimental validation

      
graph LR;
    Millman_2022[Millman et al., 2022] --> Origin_0
    Origin_0[ Type I
Escherichia coli 
2597791081, 2597791080] --> Expressed_0[Escherichia coli]
    Expressed_0[Escherichia coli] ----> T2 & T4 & T6 & LambdaVir & T5 & SECphi27
    Millman_2022[Millman et al., 2022] --> Origin_1
    Origin_1[ Type I
Escherichia coli 
2720391838, 2720391839] --> Expressed_1[Escherichia coli]
    Expressed_1[Escherichia coli] ----> LambdaVir
    Millman_2022[Millman et al., 2022] --> Origin_2
    Origin_2[ Type II
Escherichia coli 
2586378093] --> Expressed_2[Escherichia coli]
    Expressed_2[Escherichia coli] ----> SECphi17
    subgraph Title1[Reference]
        Millman_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
        LambdaVir
        T5
        SECphi27
        LambdaVir
        SECphi17
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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10.1101/2022.12.12.520048
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