FIG. 1.

Disulfide bond formation in the Escherichia coli periplasm. Disulfide bonds are introduced by DsbA, which is then recycled by the inner membrane (IM) protein DsbB. DsbB generates disulfides de novo from quinone reduction. The electrons are then transferred to the respiratory chain. Non-native disulfides introduced by DsbA in proteins with multiple cysteine residues are corrected by the protein disulfide isomerase DsbC. DsbC is maintained reduced in the periplasm by the IM protein DsbD. DsbD transfers electrons from the cytoplasmic thioredoxin system to the periplasm. Black arrows indicate the flow of electrons (To see this illustration in color, the reader is referred to the web version of this article at www.liebertpub.com/ars.)