A predicted immunity protein with an alpha+beta fold and conserved tryptophan,tyrosine and an acidic residues. Proteins containing this domain are present in bacterial polymorphic toxin systems as an immediate gene neighbor of the toxin gene, which usually contains toxin domains of the ColD/E5, Tox-REase-4, Ntox49 or Ntox14 families [1]. The domain is also found in heterogeneous polyimmunity loci.

1: Polymorphic toxin systems: comprehensive characterization of trafficking modes, processing, mechanisms of action, immunity and ecology using comparative genomics. Zhang D, de Souza RF, Anantharaman V, Iyer LM, Aravind L; Biol Direct. 2012;7:18. PMID:22731697