title: Binding Interactions of Agents That Alter α-Synuclein Aggregation.
abstract: Further examination of peptides with well-folded antiparallel β strands as inhibitors of amyloid formation from α-synuclein has resulted in more potent inhibitors. Several of these had multiple Tyr residues and represent a new lead for inhibitor design by small peptides that do not divert α-synuclein to non-amyloid aggregate formation. The most potent inhibitor obtained in this study is a backbone cyclized version of a previously studied β hairpin, designated as WW2, with a cross-strand Trp/Trp cluster. The cyclization was accomplished by adding a d-Pro-l-Pro turn locus across strand termini. At a 2:1 peptide to α-synuclein ratio, cyclo-WW2 displays complete inhibition of β-structure formation. Trp-bearing antiparallel β-sheets held together by a disulphide bond are also potent inhibitors.15N HSQC spectra of α-synuclein provided new mechanistic details. The time course of15N HSQC spectral changes observed during β-oligomer formation has revealed which segments of the structure become part of the rigid core of an oligomer at early stages of amyloidogenesis and that the C-terminus remains fully flexible throughout the process. All of the effective peptide inhibitors display binding-associated titration shifts in15N HSQC spectra of α-synuclein in the C-terminal Q109-E137 segment. Cyclo-WW2, the most potent inhibitor, also displays titration shifts in the G41-T54 span of α-synuclein, an additional binding site. The earliest aggregation event appears to be centered about H50 which is also a binding site for our most potent inhibitor.
authors.affiliation: Department of Chemistry, University of Washington, Seattle, WA 98195.
authors.forename: K
authors.initials: K
authors.lastname: Sivanesam
authors.affiliation: Department of Chemistry, University of Washington, Seattle, WA 98195.
authors.forename: A
authors.initials: A
authors.lastname: Byrne
authors.affiliation: Department of Biology, University of Padua, 35121 Padova, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Bisaglia
authors.affiliation: Department of Biology, University of Padua, 35121 Padova, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Bubacco
authors.affiliation: Department of Chemistry, University of Washington, Seattle, WA 98195.
authors.forename: N
authors.initials: N
authors.lastname: Andersen
keywords: NMR titration shifts; Parkinson’s disease; amyloidogenesis; β-hairpins