FIG. 1.

Models for disulfide-bond formation in the periplasm of E. coli. The solid black rightward arrow indicates the oxidative folding reaction catalyzed by DsbA. In the instance in which the first folding reaction resulted in a misoxidized protein, DsbC may repair it by acting as a reductase (dotted arrow) or an isomerase (not shown in this figure) of the incorrect disulfide bond. The thinner arrows indicate the flow of reducing equivalents. Q, quinones (ubiquinone or menaquinone). For simplicity, DsbC, a dimeric molecule, is depicted as a monomer.