Abstract
Bovine heart cytochrome c is an all-a globular protein containing a covalently bound heme group. Prolonged incubation at 75°C in mild alkaline solution damages the prosthetic group and results in permanent unfolding of the polypeptide chain. Under this conditions, cytochrome c aggregates into fibrillar structures. Characterization by transmission electron microscopy and thioflavin-T binding assays shows that these species posses the characteristics of fibrils associated with the family of amyloid diseases. Our findings indicate that destabilization of the native fold of this highly a-helical protein can lead to its polymerization into ß-sheet rich structures and suggest that this process does not depend on the population of partially folded monomeric states with extensive ß-sheet structure.