DsbG, a protein disulfide isomerase with chaperone activity

DsbG, a protein disulfide isomerase present in the periplasm of Escherichia coli, is shown to function as a molecular chaperone. Stoichiometric amount s of DsbG are sufficient to prevent the thermal aggregation of two classica l chaperone substrate proteins, citrate synthase and luciferase. DsbG was a lso shown to interact with refolding intermediates of chemically denatured citrate synthase and prevents their aggregation in vitro. Citrate synthase reactivation experiments in the presence of DsbG suggest that DsbG binds wi th high affinity to early unstructured protein folding intermediates. DsbG is one of the first periplasmic proteins shown to have general chaperone ac tivity. This ability to chaperone protein folding is likely to increase the effectiveness of DsbG as a protein disulfide isomerase.