Structure of NEIL1 (truncated form lacking 95 amino acids at the C-terminal domain (20)) with the protein depicted as a ribbon cartoon and in rainbow coloring from blue, N-terminus, to red, C-terminus. The key catalytic residue (P2) and the relevant residues that are changed in the variant alleles (G83, C136, A51, P68, and G245) are highlighted in ball-and-stick mode and labeled.