Involved in disulfide bond formation. DsbG and DsbC are part of a periplasmic reducing system that controls the level of cysteine sulfenylation, and provides reducing equivalents to rescue oxidatively damaged secreted proteins such as ErfK, YbiS and YnhG. Probably also functions as a disulfide isomerase with a narrower substrate specificity than DsbC. DsbG is maintained in a reduced state by DsbD. Displays chaperone activity in both redox states in vitro. Homodimer. Interacts with ErfK, YbiS and YnhG. No visible phenotype. Belongs to the thioredoxin family. DsbC subfamily. Extended N-terminus.