Conformational switching in PolyGln amyloid fibrils resulting from a single amino acid insertion.
The established correlation between neurodegenerative disorders and intracerebral deposition of polyglutamine aggregates motivates attempts to better understand their fibrillar structure. We designed polyglutamines with a few lysines inserted to overcome the hindrance of extreme insolubility and two D-lysines to limit the lengths of β-strands. One is 33 amino acids long (PolyQKd-33) and the other has one fewer glutamine (PolyQKd-32). Both form well-dispersed fibrils suitable for analysis by electron microscopy. Electron diffraction confirmed cross-β structures in both fibrils. Remarkably, the deletion of just one glutamine residue from the middle of the peptide leads to substantially different amyloid structures. PolyQKd-32 fibrils are consistently 10-20% wider than PolyQKd-33, as measured by negative staining, cryo-electron microscopy, and scanning transmission electron microscopy. Scanning transmission electron microscopy analysis revealed that the PolyQKd-32 fibrils have 50% higher mass-per-length than PolyQKd-33. This distinction can be explained by a superpleated β-structure model for PolyQKd-33 and a model with two β-solenoid protofibrils for PolyQKd-32. These data provide evidence for β-arch-containing structures in polyglutamine fibrils and open future possibilities for structure-based drug design.
Laboratory of Structural Biology, National Institute of Arthritis, Musculoskeletal, and Skin Diseases, National Institutes of Health, Bethesda, Maryland.
Rick K
RK
Huang
Laboratory of Structural Biology, National Institute of Arthritis, Musculoskeletal, and Skin Diseases, National Institutes of Health, Bethesda, Maryland; Electron Microscopy Laboratory, Cancer Research Technology Program, Leidos Biomedical Research, Frederick National Laboratory for Cancer Research, Frederick, Maryland.
Ulrich
U
Baxa
Centre de Recherches de Biochimie Macromoléculaire, CNRS, University of Montpellier 1 and 2, Montpellier, France.
Gudrun
G
Aldrian
Centre de Recherches de Biochimie Macromoléculaire, CNRS, University of Montpellier 1 and 2, Montpellier, France.
Abdullah B
AB
Ahmed
Department of Biology, Brookhaven National Laboratory, Upton New York.
Joseph S
JS
Wall
Laboratory of Structural Biology, National Institute of Arthritis, Musculoskeletal, and Skin Diseases, National Institutes of Health, Bethesda, Maryland; Department of Structural Cell Biology, Max-Planck-Institute of Biochemistry, Am Klopferspitz 18, Martinsried, Germany.
Naoko
N
Mizuno
Chemistry of Interfaces, Luleå University of Technology, Luleå, Sweden; Department of Physics, Warwick University, Coventry, United Kingdom.
Oleg
O
Antzutkin
Laboratory of Structural Biology, National Institute of Arthritis, Musculoskeletal, and Skin Diseases, National Institutes of Health, Bethesda, Maryland. Electronic address: stevena@mail.nih.gov.
Alasdair C
AC
Steven
Centre de Recherches de Biochimie Macromoléculaire, CNRS, University of Montpellier 1 and 2, Montpellier, France; Institut de Biologie Computationnelle, Montpellier, France; University ITMO, 197101 St. Petersburg, Russia. Electronic address: andrey.kajava@crbm.cnrs.fr.
Andrey V
AV
Kajava
D019943:Amino Acid Substitution; D016229:Amyloid beta-Peptides / Q000737:chemistry* / Q000235:genetics*; D006863:Hydrogen-Ion Concentration; D010455:Peptides; D055503:Protein Multimerization; D017433:Protein Structure, Secondary
D016229:Amyloid beta-Peptides; D010455:Peptides; C097188:polyglutamine