During FeS cluster biogenesis, ferredoxin and frataxin use overlapping binding sites on yeast cysteine desulfurase Nfs1

Abstract

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

“…Such behavior is suggested by our work (Supplementary Fig. 5 ), NMR data showing only 65% of FXN being bound to (Zn-NIAU) 2 under stoichiometric conditions 30 , and recent biochemical studies 33 . Hence, in our (Fe-NIAUX) 2 Mössbauer sample, the fraction of non-FXN-bound (Fe-NIAU) 2 complex likely accounts for the Mössbauer parameters of component 1.…”

“…1 and 2 ). The partial occupancy of the FXN binding site is best explained by the relatively weak affinity of FXN for the core ISC complex 16 , 30 , 33 . This fact was also evident from size exclusion chromatography (SEC) of the (Fe-NIAUX) 2 complex.…”

Structural evidence for two-stage binding of mitochondrial ferredoxin 2 to the core iron-sulfur cluster assembly complex

“…Overall, our structures fit to the model derived from biochemical studies that de novo [2Fe-2S] cluster biosynthesis by the core ISC complex is a highly concerted process with FXN and FDX2 binding sequentially rather than simultaneously ( 31 ) (Fig. 5).…”

“…The conserved arginine residues of NFS1' (Arg272, Arg275, Arg277, Arg289), which electrostatically interact with FDX2, also serve as the binding site for FXN (primarily via its residues Glu108, Glu111, Glu121 and Asp124) (18,37). It was previously suggested that ferredoxin and frataxin compete for binding in homologous bacterial and yeast complexes (29)(30)(31). In the bacterial system, Kim et al (30) found that ferredoxin, IscU and CyaY (FXN homolog) compete for an overlapping binding site on IscS (NFS1 homolog).…”

“…Despite several attempts to map ferredoxin binding to the core ISC complex, the precise interaction remains unknown. Competitive binding of bacterial frataxin (CyaY) and ferredoxin (Fdx) on the IscS dimer was proposed from nuclear magnetic resonance (NMR) spectroscopy ( 29, 30 ) and more recently from biochemical experiments using the yeast system ( 31 ) suggesting that the proteins bind in a sequential and transient fashion. In contrast, a model based on NMR data (recording the interaction of yeast ferredoxin (Yah1) with Isu1) and small-angle X-ray scattering (SAXS) envelopes of Chaetomium thermophilum homologues of the ISC machinery suggested a simultaneous binding of frataxin and ferredoxin to distinct sites ( 13 ).…”