Figure 6: Molecular model for the function of FXN in the ISC machinery.
From: Mammalian frataxin directly enhances sulfur transfer of NFS1 persulfide to both ISCU and free thiols
In the presence of FXN, the rates of two reactions are enhanced (a) sulfur transfer to ISCU and (b) sulfur transfer to free thiol-containing molecules (RSH) such as L-cysteine and GSH. The rate constants are indicated. For comparison of the rates of transfer to ISCU and RSH, a first-order rate constant for sulfur transfer to RSH has been computed assuming a concentration of 100 μM of L-cysteine that is close to the physiological concentration50.
