Selected domain architectures of HEPN proteins. The domains are not drawn to scale. Domain architectures are labeled with a representative gene name, the Genbank identifier (gi) number, and the species name separated by semicolons. The labels of eukaryotes are colored green. The generic functional categories are shown in red letters. Uncharacterized globular domains of limited phyletic spread are shown with a grey rectangle. Domain names of most domains follow the Pfam database or literature  (also see Additional file 1). Non-standard domain abbreviations: Ank – Ankyrin; CARF- CRISPR/Cas-associated Rossmann fold domain; PlipaseD – Phospholipase D; Taminase – Transglutaminase; TM – transmembrane helix; Helical – Helical domain.