Oxidation of two cysteine residues leads to the formation of a disulfidebond and the concomitant release of two electrons. The formation of disulfide bonds is a required step in the folding pathway of many secreted proteins.

In bacteria, disulfide bonds are introduced exclusively in the periplasm. The enzymes responsible are members of the Dsb (Disulfide bond) protein family: DsbA and DsbB, which are involved in disulfide bond formation and DsbC, DsbG and DsbD, which are involved in disulfide bond isomerization.

In contrast, oxidation of cysteine residues is harmful to most cytoplasmic proteins and may lead to protein misfolding and aggregation. Both eukaryotic and prokaryotic cells possess mechanisms to ensure that cytoplasmic cysteines are kept reduced. These mechanisms involve enzymes of the thioredoxin and glutaredoxin systems.

In our group, we study proteins involved in disulfide bond formation or reduction in Escherichia coli by different biochemical, structural and genetic techniques.