A predicted toxin of the restriction endonuclease fold present in bacterial polymorphic toxin systems. In bacterial polymorphic toxin systems, the toxin is exported by the type 2, type 5, type 6, or PrsW-peptidase dependent secretion system. Versions of this domain are also found in caudoviruses [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