The 5–55 single-disulphide intermediate in folding of bovine pancreatic trypsin inhibitor

AbstractAn analogue of the BPTI folding intermediate that contains only the disulphide bond between Cys-5 and Cys-55 has been prepared by mutation or the other four Cys residues to Ser. On the basis of its circular dichroism and 1H-nuclear magnetic resonance spectra and its electrophoretic mobility, this intermediate is shown to be at least partially folded at low temperatures. This probably accounts for several of the unique properties of this intermediate observed during folding