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Figure 2.
(a) Stereoview of DNA-free structure with coordination of the
active-site phosphate and three Zn^2+ ions. Omit map is
contoured at 2  (light
blue) and 4 (dark
blue) for the bound phosphate group. (b) AP DNA complex
stereoview showing the three–metal ion active site (green
spheres), residues Arg37, Tyr72 and Gln261 (pink), and bound DNA
substrate with both the AP-site sugar and phosphate moieties and
the cognate nucleotide (orange) flipped out from the DNA base
stack. The 2F[o] - F[c] electron density map is contoured at 1
(blue
mesh). (c) Stereoview of DNA substrate complex binding to
active-site metal ions. Omit map (contoured at 2 ,
pink mesh) shows the intact phosphodiester bond (black arrow)
that constrains the Zn[3] to Cyt6 O[3]' distance to 2.7 Å.
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