Found in type sIX effector (FIX) domain of unknown function co-occurring with RhsA domains with RHS repeats
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 co-occurs with C-terminal RhsA-like domain, which contains extended repeat regions and RHS repeats. Some in this family have additional C-terminal domains such as AAH, a predicted nuclease domain with conserved AHH motif that is found in bacterial polymorphic toxin systems and functions as a toxin module.