Figure 4: Influence of FXN on the reduction of NFS1 and ISCU persulfides.
From: Mammalian frataxin directly enhances sulfur transfer of NFS1 persulfide to both ISCU and free thiols
(a) Kinetics of NFS1 persulfide reduction in mixtures containing the NI complex alone (25 μM) or the NI complex (25 μM) and equimolar amounts of ISCU and/or FXN, monitored by alkylation assay. The reaction was initiated by DTT (1 mM) and analysed under reducing conditions. The reduction of NFS1 persulfide was characterized by appearance of the NFS1+7 species. The ‘v’ symbol indicates the time to reach 50% reduced NFS1. (b) Graphical representation of NFS1 persulfide reduction kinetics determined from quantification of the gels in a. The percentage of NFS1-SSH is defined by the amount of the +6 species relative to the sum (+7 + +6). The solid line represents the best fit using a second-order rate equation. (c) Kinetics of ISCU persulfide reduction in the NIU and NIUF complexes (25 μM) monitored by alkylation assay. The reaction is initiated with DTT (1 mM) and analysed under reducing conditions. The reduction of ISCU-SSH is characterized by the appearance of the +4 species corresponding to non-persulfurated ISCU. (d) Graphical representation of ISCU persulfide (ISCU-SSH) reduction kinetics in the NIU and NIUF complexes, determined by quantification of the gels in c. The solid line represents the best fit using a second-order rate equation.
