Figure 2.

A. Characteristic motifs in family I–V and family VI. Displayed are characteristic motifs (Motifs A and B) for family I–V and family VI UDG enzymes (the distinct HhH Motif and the Motif for the Iron-Sulfur Cluster). Highlighted (shaded) are active site residues of the catalytic water-activating loop as well as the Leu-intercalation loop for families I–V, and the catalytic water-activating loop in the HhH Motif as well as the conserved Cys residues of the Iron-Sulfur Cluster for family VI. The conserved catalytic Asp residue in the HhH Motif of family VI enzymes is also shaded. Except for family VI amino acid sequences are taken from structures supplemented by other sequences in the same family with secondary assignments based on the first listed structure in family I-V UDGs. The shown sequence alignment is an updated version of the sequence alignment described by Chung et al. with additional sequences, secondary structure assignments and structures provided. Structures and sequences are discussed in the subsections for each family.¹² B. Phylogenetic tree of sequence alignment [Fig. 2(A)] for the UDG superfamily. Families I–VI (includes subfamilies in family VI) are labeled. Sequence IDs or PDB IDs are shown at each branch.