Alpha + beta domain. Found fused to the N-terminus of the c2405 family of HEPN domains and in few cases to Ymh [1].

1: Comprehensive analysis of the HEPN superfamily: identification of novel roles in intra-genomic conflicts, defense, pathogenesis and RNA processing. Anantharaman V, Makarova KS, Burroughs AM, Koonin EV, Aravind L; Biol Direct. 2013;8:15. PMID:23768067