Amyloid Peptides

Beta-Amyloid (Aß) peptides, made up of long, insoluble ordered fibers, are glycoproteins deposited extracellularly in tissues in amyloidosis. These peptides are generated as cleavage products 39 to 43 amino acids in length from the membrane protein, Amyloid Precursor Protein (APP) by two proteases, ß-secretase and γ-secretase. Aßs are amphiphilic peptides with a hydrophilic N-terminal domain (residues 1 to 28) and a hydrophobic C-terminal (residues 29 to 40), the latter corresponding to a part of the transmembrane domain of APP. Heterogeneity at both ends of the peptides is known to affect the toxicity of beta-amyloid peptides. Amyloid deposits are insoluble and the core component of these plaques are Aß peptides that are 39 to 42 amino acid residues in length with a molecular mass of approximately 4 kDa. ß-Amyloid assembly into fibrils is initiated by a conformational transition from random coil to ß-sheet and a nucleation-dependent aggregation process.