A peptide hairpin inhibitor of amyloid beta-protein oligomerization and fibrillogenesis.

Amyloid beta-protein (Abeta) self-assembly is linked strongly to Alzheimer's disease. We found that PP-Leu, a tridecapeptide analogue of broad-spectrum antiviral peptides termed theta-defensins, potently inhibits Abeta oligomer and fibril formation. This effect appeared to be mediated through sequestration of the amyloidogenic Abeta peptide in colloid-like assemblies. PP-Leu comprises a turn formed by a d-Pro-l-Pro amino acid dyad and stabilized by a disulfide bond, a motif that was exceptionally resistant to endoproteinase K digestion. This combination of assembly inhibitory activity and protease resistance suggests that PP-Leu may have potential therapeutic value.