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. Author manuscript; available in PMC: 2016 May 13.
Published in final edited form as: Q Rev Biophys. 2012 Jul 31;45(3):257–299. doi: 10.1017/S0033583512000054

Fig. 1.

Fig. 1

Supercoiling and protein–DNA interactions. Top left: the bacteriophage 434 repressor (PDB ID: 3CRO.pdb) has an enhanced affinity for overwound DNA (Koudelka, 1998). Top right: Hin recombinase (PDB ID: 1HCR.pdb) will only bind to a site containing a CAG/CTG triplet when the DNA is supercoiled (Bae et al. 2006). Bottom left: the FIS protein (PDB ID: 3JRE.pdb) is both a transcription factor and a nucleoid-associated protein that constrains negative supercoils (Stella et al. 2010). Bottom right: MerR (PDB ID: 1R8E.pdb) is a bacterial repressor that on binding Hg (II) activates mercury resistance genes by untwisting the DNA-binding site (Ansari et al. 1992).