FIGURE 10.
Mössbauer spectra of the O2-exposed reconstituted NStrepChlR transcription regulator. Mössbauer spectra recorded for 57Fe-labeled, anoxically reconstituted NStrepChlR (630 μm homodimeric NStrepChlR) (top) and after exposure of the anoxic sample (middle) for 15 min to atmospheric oxygen are shown. The spectra were recorded at a temperature of 4.2 K and in a magnetic field of 53 mT applied parallel to the γ beam. On the anoxic-oxic difference spectrum (bottom, vertical bars), the simulations corresponding to the [4Fe-4S]2+ and [2Fe-2S]2+ clusters are shown in blue and green, respectively, whereas the red trace corresponds to their summation. The arrow indicates the high energy line of the high-spin Fe(II) formed upon O2 exposure.