The Mokosh system was discovered in *E. coli* by examining clusters of genes enrinched in defense islands :ref{doi=10.1016/j.chom.2022.09.017}. 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 in the active site of the PLD nuclease disrupt phage defense. The system is divided in 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 :ref{doi=10.1101/2022.12.12.520048}. The system gets its name from the goddess protector of women's destiny in Slavic mythology :ref{doi=10.1016/j.chom.2022.09.017}.
## Molecular mechanisms
As far as we are aware, the molecular mechanism is unknown.
## Example of genomic structure
The Mokosh system have been describe in a total of 2 subsystems.
