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Figure 4.
Figure 4. Extension of a G•T Mismatch by Successive
Rounds of ReplicationThe conformation of the G•T mismatch is
shown at each position (left), including interacting water
molecules (red spheres). Dashed lines indicate potential
hydrogen bonds. At the n-3 and n-4 positions, hydrogen bonds are
shown between groups within the appropriate distance (≤3.2
Å) and correspond to tautomerization or ionization of one
of the bases (see text). A schematic representation (right) of
the mismatch complex, drawn and color coded as described in
Figure 1, Figure 2 and Figure 3, indicates regions of the
polymerase active site that are disrupted upon binding of the
mismatch (red line). Mismatch binding at positions n-1 to n-4
along the DNA duplex binding region (gray) results in a
distorted open conformation at the polymerase active site as
described by mechanism 1 (Figure 3). The normal open
conformation observed with homoduplexes is fully restored when
the mismatch is bound at the n-6 position.
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