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Figure 4.
Figure 4 Comparative views (Kraulis, 1991[Kraulis, P. J. (1991).
J. Appl. Cryst. 24, 946-950.]; Merritt & Bacon, 1997[Merritt, E.
A. & Bacon, D. J. (1997). Methods Enzymol. 277, 505-524.]) of
the protein-DNA binding sites of the (a) form IVa and the (b)
form IVb structures. In each view, the characteristic ion-pair
between Asp114 and Arg116 is shown with black dotted lines.
Green dotted lines denote hydrogen bonds whose distances range
from 2.4 to 3.3 Å. Magenta dashed lines represent contacts
whose distances are greater than 3.3 Å and less than 3.8 Å.
Note the difference in the disposition of the Asp114-Arg116 ion
pair in its interaction with the nucleic acid in the form IVa
versus the IVb structure. Note the absence of contacts to the
DNA from Tyr64 in the form IVb structure.
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