S. aureus NrdH and TrxA reduction of insulin disulfides. The assay was performed in the presence of 1 mM DTT and increasing concentrations of 2 μM (▪), 4 μM (▴), and 8 μM (•) the NrdH protein (A) and in the presence of 2 μM (□), 4 μM (▵), and 8 μM (○) TrxA (B). Controls were no DTT added (×), no NrdH added (⧫), and no TrxA added (⋄).