Found in type sIX effector (FIX) domain of unknown function co-occurring with RhsA, AHH or HNH 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 co-occurs with C-terminal RhsA-like domain which contains extended repeat regions and RHS repeats. Some in this subfamily 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, and HNH endonuclease domain, which usually contains a conserved HNH motif in the sequence. Some members also contain additional N-terminal VgrG or PAAR or PAAR-like (i.e., DUF4280) domain.
Jiyao W et al.(2023). "The conserved domain database in 2023.",