Formation and seeding of amyloid fibrils from wild-type hen lysozyme and a peptide fragment from the beta-domain

Wild-type hen lysozyme has been converted from its soluble native state into highly organized amyloid fibrils. In order to achieve this conversion, conditions were chosen to promote partial unfolding of the native globular fold and included heating of low-pH solutions and addition of organic solvents. Two peptides derived from the beta-sheet region of hen lysozyme were also found to form fibrils very readily. The properties and morphologies of the amyloid fibrils formed by incubation either of the protein or the peptides are similar to those produced from the group of proteins associated with clinical amyloidoses. Fibril formation by hen lysozyme was substantially accelerated when aliquots of solutions in which fibrils of either one of the peptides or the full-length protein had previously formed were added to fresh solutions of the protein, revealing the importance of seeding in the kinetics of fibril formation. These findings support the proposition that the beta-domain is of particular significance in the formation of fibrils from the full-length protein and suggest similarities between the species giving rise to fibril formation and the intermediates formed during protein folding.