FIG. 3.

Reduction of oxidized proteins by TRX. Thioredoxin (TRX) reduces oxidized proteins containing a disulfide through the formation of a mixed disulfide intermediate involving nucleophilic attack by Cys 32 of the CXXC motif. The mixed disulfide is then resolved by Cys 35, resulting in the formation of a disulfide bond in thioredoxin. Ribbon renderings are shown for the reduced (PDB identifier, 1ERT) and oxidized thioredoxin (PDB identifier, 1ERU) along with the Cys residues of the CXXC motif in black-stick renderings.