Found in type sIX effector (FIX) domain of unknown function co-occurring with Ntox15, endonuclease, or RHS repeat domain
The Found in type sIX effector (FIX) domain is found N-terminal to known toxin domains and is genetically and functionally linked to type VI secretion system (T6SS), a widespread mechanism used by Gram-negative bacteria to antagonize neighboring cells. In Vibrio parahaemolyticus, it also co-occurs with C-terminal nuclease toxin PoNe (Polymorphic Nuclease effector) which is associated with several toxin delivery systems including type V, type VI, and type VII. In this subfamily, members contain a FIX domain that generally co-occurs with the C-terminal Ntox15 (Novel toxin 15), a predicted RNase toxin that possesses a conserved HxxD motif, as well as with domains such as DNA/RNA non-specific endonuclease, RhsA domain regions with extende RHS repeats, or DUF4112. Some members also contain an N-terminal PAAR-like (i.e., DUF4280) domain.
Jiyao W et al.(2023). "The conserved domain database in 2023.",