Poorly-understood domain observed N-terminal to restriction endonuclease (REase) domain, which is part of a conserved three-gene island also containing a DinG-type helicase and the pPIWI_RE module. This three gene island is predicted to form a conflict system which targets R-loop formation of invasive plasmids during plasmid replication [1].

1: Two novel PIWI families: roles in inter-genomic conflicts in bacteria and Mediator-dependent modulation of transcription in eukaryotes. Burroughs AM, Iyer LM, Aravind L; Biol Direct. 2013;8:13. PMID:23758928