Fig. 1
a, Structure of Lla-Fpg (1XC8) used as a starting model. The protein is colored according to its secondary structure (cyan, α helices; magenta, β sheets; coral, loops); the DNA is colored by atom type (green, C; blue, N; red, O; orange, P). An orange line is drawn through P atoms in DNA to highlight an axial kink induced by Fpg binding. b, Mechanism of oxoG excision by Fpg proposed from the structural data [35]. The SN2 displacement occurs in the C1′ → O4′ direction rather than in the C1′ → N9 direction. c, Schematic representation of the modeled DNA duplex and numbering of DNA bases and phosphates (p). N(0) is either C or A. Positions of Arg109 and Phe111 in the complex are indicated. d, Schematic position of the damaged base relative to the sugar plane in the structures of free oxoG-containing DNA (183D, [56]) or Fpg–DNA complexes containing various purine-derived lesions everted into the active site (1XC8, 3C58, 4CIS and 1R2Y; see structure details in the text)