Multiple alignment of the HEPN superfamily. The multiple sequence alignment includes the conserved blocks based on the MUSCLE alignment , which was corrected manually on the basis of HHpred  and PSI-BLAST results . Due to the low similarity, the alignment of helices 1, 2.1 and 4 should be considered tentative. Secondary structure, which is a consensus between the proteins with solved structures, is shown above the alignment; ‘H’ indicates α-helix. The sequences are denoted by their GI numbers and species names. The HEPN family to which each sequence belongs is indicated after the species name. Positions of the first and the last residues of the aligned region in the corresponding protein are indicated for each sequence. The PDB identifiers for proteins with solved structure are indicated on the right. The numbers (of amino acid residues) within the alignment represent poorly conserved inserts that are not shown. The coloring is based on the consensus shown underneath the alignment; ‘h’ indicates hydrophobic residues (WFYMLIVACTH), ‘p’ indicates polar residues (EDKRNQHTS),‘s’ indicates small residues (ACDGNPSTV). Predicted catalytic amino acids are shown by reverse shading. GI and species name is underlined if the HEPN domain has lost the conserved Rx4-6H motif.