David Auble
The MuR-DNA complex (1g4d) shows how a "winged helix" monomer interacts with DNA. Most helix-turn-helix proteins (e.g. Cro) bind DNA as dimers, but in this case the interaction of the MuR HTH motif with DNA is stabilized by a β "wing" that also contacts DNA. In the default cartoon display you can pick out the HTH recognition helix lying in the major groove and the β loop which is inserted into the adjacent minor groove. The complex is stabilized by only one base-specific hydrogen bond, but there are many hydrophobic interactions established in the major groove, as well as electrostatic interactions with DNA phosphates.
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