Figure 3.

ΔAPE1–DNA complex structures with purine–purine mismatches. A close-up view (left) of the base-pairing interactions and a side view (right) of the superposition of the (a) G·G, (b) A_O·G_A and (c) A·A mismatches with a G_O·C_A reference structure (gray lines; PDB entry 5dfi). Black dotted lines indicate potential hydrogen-bonding interactions with distances. A yellow dot is an expected proton donor with respect to the Watson–Crick donor/acceptor pairs. A red dot denotes a possible proton donor following protonation of the typical proton acceptor. The double arrow with a dashed line denotes the C1′–C1′ distance.