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. Author manuscript; available in PMC: 2014 Jul 23.
Published in final edited form as: Mol Microbiol. 2012 Oct 17;87(3):478–492. doi: 10.1111/mmi.12052

Fig. 4.

Fig. 4

Binding isotherms of [2Fe-2S]-IscR and apo-IscR for the two Type 1 sites within the PiscR region. A) Sequences of IscR binding sites A (underlined) and B (double underlined) within PiscR. Numbers indicate the distance relative to the +1 transcription start site. B) DNA binding isotherms of wild-type [2Fe-2S]-IscR (open symbols) and the clusterless mutant protein IscR-C92A/C98A/C104A (closed symbols) measured as a change in anisotropy under anaerobic conditions. Both forms of IscR protein were incubated with 5 nM fluorescently labeled DNA containing either site A (circles) or site B (triangles) in 40 mM Tris-Cl (pH 7.9) and 150 mM KCl. C) Fraction bound corrected for fluorescence quenching of labeled PiscR sites A or B bound by [2Fe-2S]-IscR as a function of protein concentration. Error bars represent the standard errors of triplicate experiments.