A predicted immunity protein with an alpha+beta fold and a conserved arginine. Proteins containing this domain are present in bacterial polymorphic toxin systems as an immediate gene neighbour of the toxin gene, which usually contains toxin domains of the Ntox40 family [1].

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