Circular and circularly permuted forms of bovine pancreatic trypsin inhibitor.

Two novel forms of bovine pancreatic trypsin inhibitor have been prepared. The amino- and carboxyl-termini, which are in close proximity in the native conformation, were linked together in a peptide bond, thus generating a molecule with a circular backbone. The circular molecule was then cleaved between Lys15 and Ala16, to yield a linear molecule whose sequence is a circular permutation of that of bovine pancreatic trypsin inhibitor. Both of these modified forms could refold to the native conformation after being reduced, and promise to be interesting subjects for further folding experiments.