title: α-Synuclein Amyloid Fibrils with Two Entwined, Asymmetrically Associated Protofibrils.
abstract: Parkinson disease and other progressive neurodegenerative conditions are characterized by the intracerebral presence of Lewy bodies, containing amyloid fibrils of α-synuclein. We used cryo-electron microscopy and scanning transmission electron microscopy (STEM) to study in vitro-assembled fibrils. These fibrils are highly polymorphic. Focusing on twisting fibrils with an inter-crossover spacing of 77 nm, our reconstructions showed them to consist of paired protofibrils. STEM mass per length data gave one subunit per 0.47 nm axial rise per protofibril, consistent with a superpleated β-structure. The STEM images show two thread-like densities running along each of these fibrils, which we interpret as ladders of metal ions. These threads confirmed the two-protofibril architecture of the 77-nm twisting fibrils and allowed us to identify this morphotype in STEM micrographs. Some other, but not all, fibril morphotypes also exhibit dense threads, implying that they also present a putative metal binding site. We propose a molecular model for the protofibril and suggest that polymorphic variant fibrils have different numbers of protofibrils that are associated differently.
authors.affiliation: From the Laboratory of Structural Biology Research, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: Altaira D
authors.initials: AD
authors.lastname: Dearborn
authors.affiliation: the Department of Biology, Brookhaven National Laboratory, Upton, New York 19973.
authors.forename: Joseph S
authors.initials: JS
authors.lastname: Wall
authors.affiliation: From the Laboratory of Structural Biology Research, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: Naiqian
authors.initials: N
authors.lastname: Cheng
authors.affiliation: From the Laboratory of Structural Biology Research, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: J Bernard
authors.initials: JB
authors.lastname: Heymann
authors.affiliation: the Centre de Recherches de Biochimie Macromoléculaire, CNRS, University of Montpellier, Montpellier 34172, France, the University ITMO, Institute of Bioengineering, 197101 St. Petersburg, Russia.
authors.forename: Andrey V
authors.initials: AV
authors.lastname: Kajava
authors.affiliation: the Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, California 90033, and Karunya University, Coimbatore, Tamil Nadu 641 114, India.
authors.forename: Jobin
authors.initials: J
authors.lastname: Varkey
authors.affiliation: the Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, California 90033, and.
authors.forename: Ralf
authors.initials: R
authors.lastname: Langen
authors.affiliation: From the Laboratory of Structural Biology Research, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland 20892, stevena@mail.nih.gov.
authors.forename: Alasdair C
authors.initials: AC
authors.lastname: Steven
mesh_terms: D000595:Amino Acid Sequence; D000682:Amyloid / Q000737:chemistry*; D001665:Binding Sites; D020285:Cryoelectron Microscopy; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007477:Ions; D016631:Lewy Bodies / Q000378:metabolism; D017348:Microscopy, Electron, Scanning Transmission; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D017386:Sequence Homology, Amino Acid; D051844:alpha-Synuclein / Q000737:chemistry*
chemical_list: D000682:Amyloid; D007477:Ions; D051844:alpha-Synuclein
keywords: amyloid; cross-β structure; cryo-electron microscopy; fibril; metalloprotein; microscopic imaging; microscopy; molecular mass measurements; scanning transmission electron microscopy; superpleated β structure