DsbA family, DsbC and DsbG subfamily; V-shaped homodimeric proteins containing a redox active CXXC motif imbedded in a TRX fold. They function as protein disulfide isomerases and chaperones in the bacterial periplasm to correct non-native disulfide bonds formed by DsbA and prevent aggregation of incorrectly folded proteins. DsbC and DsbG are kept in their reduced state by the cytoplasmic membrane protein DsbD, which utilizes the TRX/TRX reductase system in the cytosol as a source of reducing equivalents. DsbG differ from DsbC in that it has a more limited substrate specificity, and it may preferentially act later in the folding process to catalyze disulfide rearrangements in folded or partially folded proteins. Also included in the alignment is the predicted protein TrbB, whose gene was sequenced from the enterohemorrhagic E. coli type IV pilus gene cluster, which is required for efficient plasmid transfer.
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