Natural and synthetic prion structure from X-ray fiber diffraction

Abstract

A conformational isoform of the mammalian prion protein (PrP Sc ) is the sole component of the infectious pathogen that causes the prion diseases. We have obtained X-ray fiber diffraction patterns from infectious prions that show cross-␤ diffraction: meridional intensity at 4.8 Å resolution, indicating the presence of ␤ strands running approximately at right angles to the filament axis and characteristic of amyloid structure. Some of the patterns also indicated the presence of a repeating unit along the fiber axis, corresponding to four ␤-strands. We found that recombinant (rec) PrP amyloid differs substantially from highly infectious brainderived prions, both in structure as demonstrated by the diffraction data, and in heterogeneity as shown by electron microscopy. In addition to the strong 4.8 Å meridional reflection, the recPrP amyloid diffraction is characterized by strong equatorial intensity at approximately 10.5 Å, absent from brain-derived prions, and indicating the presence of stacked ␤-sheets. Synthetic prions recovered from transgenic mice inoculated with recPrP amyloid displayed structural characteristics and homogeneity similar to those of naturally occurring prions. The relationship between the structural differences and prion infectivity is uncertain, but might be explained by any of several hypotheses: only a minority of recPrP amyloid possesses a replication-competent conformation, the majority of recPrP amyloid has to undergo a conformational maturation to acquire replication competency, or inhibitory forms of recPrP amyloid interfere with replication during the initial transmission.amyloid ͉ protein ͉ neurodegeneration ͉ PrP ͉ ␤-helix

Determination of amyloid core structure using chemical shifts

“…17 Calculations were performed on five identical segments that were connected by 16-residue glycine-serine linkers. Distance restraints (Table II) enforced interstrand distances between different layers orthogonal to the fibril axis to 4.8 Å , in agreement with X-ray diffraction patterns of mammalian prions 37 and amyloid fibrils of PrP(82-146). 38 Hydrogen-bond distance restraints for parallel, in-register alignment-as shown by solid-state NMR spectroscopy of humPrP(23-144) 31 -were used.…”

Sialylation of Glycosylphosphatidylinositol (GPI) Anchors of Mammalian Prions Is Regulated in a Host-, Tissue-, and Cell-specific Manner

“…Upon conversion of PrP C into PrP Sc , the N-linked glycans and GPI are carried over, giving rise to glycosylated and GPI-anchored PrP Sc (17,18). Like amyloids formed by other amyloidogenic proteins or peptides, PrP Sc displays a cross-␤ folding pattern (19,20), a key structural feature of amyloid states. However, unlike other amyloidogenic proteins linked to neurodegenerative diseases, PrP…”

Truncated forms of the prion protein PrP demonstrate the need for complexity in prion structure

“…Infectious recombinant PrP 16 forms such structures. 5 In most cases recombinant PrP has not been found to be infectious at all, and when it is infectious, it is not clear whether the infectivity is due to a small fraction of molecules, undetected in diffraction experiments but similar in structure to naturally occurring prions, or to a distinctly structured PrP amyloid, which acts as a catalyst for the formation of the fully replication-competent infectious prion structure. This route of infection represents a pathway parallel to the natural etiology and would most likely be caused by a process of deformed templating (heterogeneous seeding).…”

“…These simple arrangements are quite distinct from those of the structurally more complex architectures found in biologically active amyloids. For example, the fungal prion HET-s and putatively the mammalian prion PrP have b-solenoidal structures 5,6,7 (Fig. 1A, B), and even the relatively small Alzheimer's-associated Ab peptide has a U-shaped 2-b-strand architecture.…”