Fig. 4: Mössbauer spectroscopy reveals an equilibrium of two distinct Fe coordination states in intermediates of [2Fe-2S] cluster synthesis on ISCU2. | Nature Communications

Fig. 4: Mössbauer spectroscopy reveals an equilibrium of two distinct Fe coordination states in intermediates of [2Fe-2S] cluster synthesis on ISCU2.

From: Mechanism and structural dynamics of sulfur transfer during de novo [2Fe-2S] cluster assembly on ISCU2

Fig. 4: Mössbauer spectroscopy reveals an equilibrium of two distinct Fe coordination states in intermediates of [2Fe-2S] cluster synthesis on ISCU2.

Spectra of the indicated complexes reconstituted with 1 eq. (NH4)257Fe(SO4)2 per ISCU2. For the detailed sample composition, see Supplementary Table 2a. U: ISCU2; X: FXN; F: FDX2. a Mössbauer spectrum recorded for 57Fe-loaded ISCU2 (Fe-U). b–d Mössbauer spectra of samples containing (NIA)2 and/or FXN in excess over ISCU2. Cysteine was added as the last component in (d) to initiate ISCU2 persulfidation. e Mössbauer spectrum in the presence of (NIAX)2, lacking ISCU2. f Mössbauer spectrum of enzymatically reconstituted [2Fe-2S]-ISCU2 from a reaction containing (NIA)2, FXN, FDX2 and FDXR in catalytic amounts, as well as Cys and NADPH. Each Mössbauer spectrum was recorded at 77 K and zero applied external field. The red lines display the best fit of the data using the components shown as black lines with parameters given in Table 3. Mössbauer data points are presented as relative transmission per velocity channel derived from detector counts (see “Methods”). Error bars indicate ±SD. g Scheme depicting the shift in equilibrium of ISCU2-bound Fe-species (components 1 and 2) by FXN binding and persulfidation (+Cys) during consecutive stages of [2Fe-2S] cluster biosynthesis on ISCU2 (Fe components 3 and 4) identified by Mössbauer spectroscopy.

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