Effects of ionic and reductive atmosphere on the conformational rearrangement in hen egg white lysozyme prior to amyloid formation

Abstract

In this study, the combined effects of pH and salt concentration on the aggregation and amyloid formation of a charge-bearing protein (hen egg white lysozyme, HEWL) were investigated, as well as the inhibition of amyloid formation by using dithiothreitol (DTT) as a denaturing agent. Amyloid formation was found to depend on the ion strength and pH of the sample solution. Rather than the total charge, the partial charge of the amyloid related residues contributes to amyloid formation at pH < isoelectric point (pI). On the other hand, at pH> pI HEWL only undergoes alkaline denaturation regardless of the ionic strength. The effect of adding different amounts of DTT at different times on amyloid formation was also investigated. These results suggested that the positions of charges on a protein and the protein secondary structure are critical for protein aggregation and amyloid formation.

Keywords: Aggregation; Amyloid; DLVO theory; Ionic strength; Isoelectric point.