The disulfide folding pathway of tick anticoagulant peptide (TAP), a Kunitz-type inhibitor structurally homologous to BPTI

Abstract

The pathway of oxidative folding of tick anticoagulant peptide (TAP, 60 amino acids and three disulfides) has been analyzed by characterization of the acid and iodoacetate trapped folding intermediates. The results reveal a high degree of heterogeneity of the one- and two-disulfide intermediates and the presence of three-disulfide scrambled species along the folding pathway. The picture of TAP folding differs significantly from the well-documented case of bovine pancreatic trypsin inhibitor (BPTI), despite the fact that both proteins share close structural homology in term of 3-D conformation and disulfide pattern.