title: Role of aromatic side chains in amyloid β-protein aggregation.
abstract: Aggregation of the amyloid β-protein (Aβ) is believed to be involved in Alzheimer's disease pathogenesis. Here we have investigated the importance of the aromatic rings at positions 19 and 20 for the aggregation rate and mechanism by substituting phenylalanine with leucine. Aggregation kinetics were monitored as a function of time and peptide concentration by thioflavin T (ThT) fluorescence, the aggregation equilibrium by sedimentation assay, structural changes using circular dichroism spectroscopy and the presence of fibrillar material was detected with cryo-transmission electron microscopy. All peptides convert from monomer to amyloid fibrils in a concentration-dependent manner. Substituting F19 with leucine results in a peptide that aggregates significantly slower than the wild type, while substitution of F20 produces a peptide that aggregates faster. The effects of the two substitutions are additive, since simultaneous substitution of F19 and F20 produces a peptide with aggregation kinetics intermediate between F19L and F20L. Our results suggest that the aromatic side-chain of F19 favors nucleation of the aggregation process and may be an important target for therapeutic intervention.
authors.affiliation: Chemistry Department and Molecular Protein Science, Lund University, P.O. Box 124, SE221 00 Lund, Sweden.
authors.forename: Risto
authors.initials: R
authors.lastname: Cukalevski
authors.forename: Barry
authors.initials: B
authors.lastname: Boland
authors.forename: Birgitta
authors.initials: B
authors.lastname: Frohm
authors.forename: Eva
authors.initials: E
authors.lastname: Thulin
authors.forename: Dominic
authors.initials: D
authors.lastname: Walsh
authors.forename: Sara
authors.initials: S
authors.lastname: Linse
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism; D016229:Amyloid beta-Peptides / Q000378:metabolism*; D002942:Circular Dichroism; D007700:Kinetics; D010446:Peptide Fragments / Q000378:metabolism*; D017433:Protein Structure, Secondary
chemical_list: D016229:Amyloid beta-Peptides; D010446:Peptide Fragments