title: Characterizing methyl-bearing side chain contacts and dynamics mediating amyloid β protofibril interactions using ¹³C(methyl)-DEST and lifetime line broadening.
abstract: Many details pertaining to the formation and interactions of protein aggregates associated with neurodegenerative diseases are invisible to conventional biophysical techniques. We recently introduced (15)N dark-state exchange saturation transfer (DEST) and (15)N lifetime line-broadening to study solution backbone dynamics and position-specific binding probabilities for amyloid β (Aβ) monomers in exchange with large (2-80 MDa) protofibrillar Aβ aggregates. Here we use (13)C(methyl)DEST and lifetime line-broadening to probe the interactions and dynamics of methyl-bearing side chains in the Aβ-protofibril-bound state. We show that all methyl groups of Aβ40 populate direct-contact bound states with a very fast effective transverse relaxation rate, indicative of side-chain-mediated direct binding to the protofibril surface. The data are consistent with position-specific enhancements of (13)C(methyl)-R₂(tethered) values in tethered states, providing further insights into the structural ensemble of the protofibril-bound state.
authors.affiliation: Department of Molecular Pharmacology, Physiology and Biotechnology, Brown University, Providence, RI 02912 (USA). nicolas_fawzi@brown.edu.
authors.forename: Nicolas L
authors.initials: NL
authors.lastname: Fawzi
authors.forename: David S
authors.initials: DS
authors.lastname: Libich
authors.forename: Jinfa
authors.initials: J
authors.lastname: Ying
authors.forename: Vitali
authors.initials: V
authors.lastname: Tugarinov
authors.forename: G Marius
authors.initials: GM
authors.lastname: Clore
mesh_terms: D000595:Amino Acid Sequence; D016229:Amyloid beta-Peptides / Q000737:chemistry* / Q000378:metabolism; D002247:Carbon Isotopes / Q000737:chemistry; D007700:Kinetics; D008969:Molecular Sequence Data; D009587:Nitrogen Isotopes / Q000737:chemistry; D019906:Nuclear Magnetic Resonance, Biomolecular; D054730:Protein Interaction Domains and Motifs
chemical_list: D016229:Amyloid beta-Peptides; D002247:Carbon Isotopes; D009587:Nitrogen Isotopes
keywords: NMR spectroscopy; amyloid β; high-molecular-weight assemblies; protein-protein interactions