Figure 1.

A comparison of the sequences (species code and GenBank accession no. in brackets) of endonuclease III-like proteins of human (hNTH1), S. pombe (Nth-Spo; Q09907), Caenorhabditis elegans (Ce; Z50874), Bacillus subtilis (Bs; P39788), and E. coli (Ec; P20625); UV N-glycosylase from Micrococcus luteus (Ml; P46303) and Mut Y of E. coli (Ec; P17802). The cysteine residues (Cys-Xaa₆-Cys-Xaa₂-Cys-Xaa₅-Cys) involved in binding the [4Fe-4S] cluster are marked with asterisks. The S. pombe endonuclease III homolog, Nth-Spo (13), has the last cysteine displaced by two residues. The highly conserved helix–hairpin–helix motif, which is thought to interact with DNA, is indicated. The hairpin consists of GVG, usually flanked by P. The proposed active site lysine residue is indicated by a solid triangle and the conserved aspartic acid is marked with a dot. The potential nuclear targeting sequences in the N-terminal domain of the human protein are underlined. Positions with a majority of identical residues are boxed (black) and shown in the consensus. Amino acids similar to the consensus are shaded grey. The C-terminal regions that extend beyond the termini of the human and E. coli proteins are not shown.