Elongated oligomers assemble into mammalian PrP amyloid fibrils.
In prion diseases, the mammalian prion protein PrP is converted from a monomeric, mainly alpha-helical state into beta-rich amyloid fibrils. To examine the structure of the misfolded state, amyloid fibrils were grown from a beta form of recombinant mouse PrP (residues 91-231). The beta-PrP precursors assembled slowly into amyloid fibrils with an overall helical twist. The fibrils exhibit immunological reactivity similar to that of ex vivo PrP Sc. Using electron microscopy and image processing, we obtained three-dimensional density maps of two forms of PrP fibrils with slightly different twists. They reveal two intertwined protofilaments with a subunit repeat of approximately 60 A. The repeating unit along each protofilament can be accounted for by elongated oligomers of PrP, suggesting a hierarchical assembly mechanism for the fibrils. The structure reveals flexible crossbridges between the two protofilaments, and subunit contacts along the protofilaments that are likely to reflect specific features of the PrP sequence, in addition to the generic, cross-beta amyloid fold.
MRC Prion Unit and Department of Neurodegenerative Disease, Institute of Neurology, University College London, Queen Square, London WC1N 3BG, UK.
M Howard
MH
Tattum
Sara
S
Cohen-Krausz
Kanjana
K
Thumanu
Christopher W
CW
Wharton
Azadeh
A
Khalili-Shirazi
Graham S
GS
Jackson
Elena V
EV
Orlova
John
J
Collinge
Anthony R
AR
Clarke
Helen R
HR
Saibil
D000682:Amyloid / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D000818:Animals; D003545:Cysteine / Q000378:metabolism; D051379:Mice; D008958:Models, Molecular; D010084:Oxidation-Reduction; D011328:Prions / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D011487:Protein Conformation; D017510:Protein Folding; D011499:Protein Processing, Post-Translational; D017433:Protein Structure, Secondary; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D020449:Repetitive Sequences, Amino Acid
D000682:Amyloid; D011328:Prions; D021122:Protein Subunits; D003545:Cysteine