title: The off-rate of monomers dissociating from amyloid-β protofibrils.
abstract: The interconversion of monomers, oligomers, and amyloid fibrils of the amyloid-β peptide (Aβ) has been implicated in the pathogenesis of Alzheimer disease. The determination of the kinetics of the individual association and dissociation reactions is hampered by the fact that forward and reverse reactions to/from different aggregation states occur simultaneously. Here, we report the kinetics of dissociation of Aβ monomers from protofibrils, prefibrillar high molecular weight oligomers previously shown to possess pronounced neurotoxicity. An engineered binding protein sequestering specifically monomeric Aβ was employed to follow protofibril dissociation by tryptophan fluorescence, precluding confounding effects of reverse or competing reactions. Aβ protofibril dissociation into monomers follows exponential decay kinetics with a time constant of ∼2 h at 25 °C and an activation energy of 80 kJ/mol, values typical for high affinity biomolecular interactions. This study demonstrates the high kinetic stability of Aβ protofibrils toward dissociation into monomers and supports the delineation of the Aβ folding and assembly energy landscape.
authors.affiliation: From the Institute of Physical Biology, Heinrich-Heine-Universität, 40204 Düsseldorf and.
authors.forename: Clara S R
authors.initials: CS
authors.lastname: Grüning
authors.forename: Stefan
authors.initials: S
authors.lastname: Klinker
authors.forename: Martin
authors.initials: M
authors.lastname: Wolff
authors.forename: Mario
authors.initials: M
authors.lastname: Schneider
authors.forename: Küpra
authors.initials: K
authors.lastname: Toksöz
authors.forename: Antonia N
authors.initials: AN
authors.lastname: Klein
authors.forename: Luitgard
authors.initials: L
authors.lastname: Nagel-Steger
authors.forename: Dieter
authors.initials: D
authors.lastname: Willbold
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Hoyer
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism; D016229:Amyloid beta-Peptides / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D046912:Multiprotein Complexes / Q000737:chemistry* / Q000378:metabolism; D017510:Protein Folding; D055503:Protein Multimerization; D055550:Protein Stability
chemical_list: D016229:Amyloid beta-Peptides; D046912:Multiprotein Complexes
keywords: Alzheimer Disease; Amyloid; Fluorescence; Kinetics; Protein Aggregation; Protein Engineering; Protein Misfolding; Scaffold Proteins; Spectroscopy