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Figure 4.
Figure 4 Comparison of an open 8oG complex and a closed T ddATP
insertion complex. The open 8oG complex (red) and a dT dATP
insertion complex (gray) were superimposed using C[ ]atoms.
The proteins are depicted as cylinders and the DNA as sticks.
Both structures are largely similar but they specifically differ
in the orientation adopted by their fingers subdomains. In the
closed structure, -helices
O and O1 pack against the incoming ddATP (blue) and the template
thymine, respectively. In the open structure, the fingers move
outwards from the palm subdomain, as shown by the 45°
rotation of the O and O1 helices relative to the closed
conformation. Residue Tyr530, which moves to the position that
would correspond to the templating base of the closed complex,
has been omitted for clarity. The templating 8oG, the 5'
template strand, and residues 532 -536 located at the junction
between helices
O and O1 are disordered in the open complex. No interpretable
electron density is observed for the metal ions or incoming
nucleotide.
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