Formation of amyloid fibrils from fully reduced hen egg white lysozyme.

The fully reduced hen egg white lysozyme (HEWL), which is a good model of random coil structure, has been converted to highly organized amyloid fibrils at low pH by adding ethanol. In the presence of 90% (v/v) ethanol, the fully reduced HEWL adopts beta-sheet secondary structure at pH 4.5 and 5.0, and an alpha-to-beta transition is observed at pH 4.0. A red shift of the Congo red absorption spectrum caused by the precipitation of the fully reduced HEWL in the presence of 90% (v/v) ethanol is typical of the presence of amyloid aggregation. EM reveals unbranched fibrils with a diameter of 2-5 nm and as long as 1-2 mum. The pH dependence of the initial structure of the fully reduced HEWL in the presence of 90% (v/v) ethanol suggests that Asp and His residues may play an important role.