Native and non-native intermediates in the BPTI folding pathway.

Recent studies of the disulfide-bonded intermediates in the refolding of bovine pancreatic trypsin inhibitor (BPTI) indicate that the most stable intermediates can take on much or all of the structure of the fully folded protein. Native-like structure in the intermediates probably causes steric inhibition of direct sequential formation of the three disulfides found in the native protein, thus accounting for the role of intramolecular rearrangements in the folding mechanism of this small protein.