The disulfide structures of scrambled hirudins

Scrambled hirudins consist of a collection of equilibrated isomers and serve as essential folding intermediates during the in vitro renaturation of hirudin (Chatrenet, B., and Chang, J.-Y. (1993) J. Biol. Chem. 268, 20988-20996). Ten fractions of scrambled hirudins have been isolated. Their disulfide structures were deduced from the analysis of thermolysin-digested peptides by amino acid sequencing and mass spectrometry. The results reveal 9 fractions of pure scrambled species, and, together, 11 species of scrambled structures have been identified. About all possible disulfide isomers of hirudin have been found to exist. The three native disulfides, Cys6-Cys14, Cys16-Cys28, and Cys22-Cys39, are detected in five different scrambled species and constitute 18% of the total disulfide bonds found in scrambled hirudins.