1H NMR analysis of the partly-folded non-native two-disulphide intermediates (30-51,5-14) and (30-51,5-38) in the folding pathway of bovine pancreatic trypsin inhibitor.

The conformational properties of analogues of the (30-51,5-14) and (30-51,5-38) disulphide intermediates in refolding of reduced BPTI, with non-native second disulphide bonds, have been characterized in detail by 1H NMR analysis. They are shown to have partly-folded conformations, very similar to that of the (30-51) one-disulphide intermediate from which they arise during folding. The non-native disulphide bonds are formed in flexible or unfolded parts of the polypeptide chain; they do not disrupt the folded portion nor do they introduce substantial non-native conformation. The conformational properties of these intermediates explain their important roles in the folding pathway.