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Figure 3.
FIG. 3. A hydrogen-bonding network connects DNA distortion
to approach of the scissile bond to the H-N-H motif metal
center. Stereo representation of the main hydrogen-bonding
interactions between the E9 DNase and the DNA minor groove in
the Zn2+ complex, with identical interactions observed in the
Mg2+-bound complex. The DNA and protein residues are cream and
green, respectively, the Zn2+ ion is magenta, and hydrogen bonds
are plotted as dotted lines. The scissile bond of the DNA can
only approach the metal ion if the DNA is distorted. This is
accomplished by the insertion of the Arg-96-Glu-100 salt bridge
into the minor groove and stabilization of this configuration
through a number of hydrogen-bonding interactions to the DNA
phosphates through residues Arg-5, Asp-51, and Arg-54.
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