The E. coli SufS–SufE sulfur transfer system is more resistant to oxidative stress than IscS–IscU

During oxidative stress in Escherichiacoli, the SufABCDSE stress response pathway mediates iron–sulfur (Fe–S) cluster biogenesis rather than the Isc pathway. To determine why the Suf pathway is favored under stress conditions, the stress response SufS–SufE sulfur transfer pathway and the basal housekeeping IscS–IscU pathway were directly compared. We found that SufS–SufE cysteine desulfurase activity is significantly higher than IscS–IscU at physiological cysteine concentrations and after exposure to H2O2. Mass spectrometry analysis demonstrated that IscS–IscU is more susceptible than SufS–SufE to oxidative modification by H2O2. These important results provide biochemical insight into the stress resistance of the Suf pathway.

► We characterize the kinetics of the SufS–SufE sulfur transfer system.
► We directly compare SufS–SufE to the IscS–IscU system from E. coli.
► SufS–SufE are more active at physiological l-cysteine levels than IscS–IscU.
► SufS–SufE activity is more resistant to oxidative stress than IscS–IscU.