Effect of protein disulfide isomerase on the regeneration of bovine ribonuclease A with dithiothreitol

The role of protein disulfide isomerase (PDI) in the regeneration of ribonu clease A with dithiothreitol (DTT) was investigated at three different temp eratures. The rates of formation of the native protein were markedly increa sed in the presence of PDI, 9-fold at 15 degrees C, 6-fold at 25 degrees C and 62-fold at 37 degrees C, respectively, In the presence of PDI, major ch anges were found in the distribution of intermediates in the three-disulfid e region at 25 and 15 degrees C and also in the one-disulfide region at 15 degrees C, with the fast accumulation of the two native-like species des-[6 5-72] and des-[40-95]. The present results indicate that PDI does not alter the two major parallel pathways involving des-[65-72] and des-[40-95] in t he regeneration of ribonuclease A with DTT. (C) 1999 Federation of European Biochemical Societies.