Method for quantitative refolding of the link module from human TSG-6

We have developed a procedure for the quantitative refolding of the Link module from human tumor necrosis factor-stimulated gene 6. This significantly simplifies the previously described method of production of this protein domain (Day et al., Protein Expression Purif. 8, 1-16, 1996). The refolding is carried out under nondenaturing conditions at pH 6.0 in the presence of a 100-fold molar excess of beta-mercaptoethanol. After 2 days the starting material, which consists of three species that differ only with respect to their disulfide bond organization, has rearranged to give a single homogeneous species with the correct disulfide bridges. This method allows the production of about 20 mg of folded protein per liter of Escherichia coli culture.