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Figure 7.
Figure 7. Stereoview of the Pol b Active Site
Superimposed structures of pol b with either Na^+ (light blue)
or Mg2+ (yellow) in the catalytic metal site A. Residues that
hydrogen bond (green) to the triphosphate moiety of the incoming
nucleotide and the active site aspartates are shown. When Na^+
occupies the catalytic metal site, O3' of the primer terminus is
3.5 and 4.7 Å from the catalytic metal and aP of the incoming
nucleotide, respectively. In contrast, with Mg2+ in the
catalytic metal site, an altered sugar pucker positions O3' of
the primer terminus 2.2 and 3.4 Å from the catalytic metal and
Pa of the incoming nucleotide, respectively.
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