A predicted immunity protein with an alpha+beta fold and a conserved glutamate residue. The domain is often fused to one or more immunity domains in poly-immunity proteins [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