Figure 1.

(A) A schematic illustration of the base-flipping process exerted by TDG during DNA repair. The lesion searching is initiated by protein-DNA interaction to form the Interrogation Complex (IC), followed by penetration of an intercalated residue Arg275 of TDG into the DNA minor groove, which results in formation of the Recognition Complex (RC). (B) The modeled structure of the IC with the key motifs highlighted in a zoomed-in image, in which the T·G mispair is colored in green/magenta, and the TDG active site residues Tyr152 and Asn191 are shown in gray sticks; the intercalation loop (Ser271–Arg281) is highlighted in blue and the intercalated residue Arg275 is shown in blue sticks; the gating region (Ile136 to Phe159) is shown in cyan. (C) The minimized structure of the RC with the mismatched dT nt flipped into the TDG active site.