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Secondary structure analysis of the scrapie-associated protein PrP 27-30 in water by infrared spectroscopy
B W Caughey1, A Dong, K S Bhat
1NIAID, National Institutes of Health, Rocky Mountain Laboratories, Hamilton, Montana 59840.
Abstract:
A protease-resistant form of the protein PrP (PrP-res) accumulates in tissues of mammals infected with scrapie, Creutzfeldt-Jakob disease, and related transmissible neurodegenerative diseases. This abnormal form of PrP can aggregate into insoluble amyloid-like fibrils and plaques and has been identified as the major component of brain fractions enriched for scrapie infectivity. Using a recently developed technique in Fourier transform infrared spectroscopy which allows protein conformational analysis in aqueous media, we have studied the secondary structure of the proteinase K resistant core of PrP-res (PrP-res 27-30) as it exists in highly infectious fibril preparations. Second-derivative analysis of the infrared spectra has enabled us to quantitate the relative amounts of different secondary structures in the PrP-res aggregates. The analysis indicated that PrP-res 27-30 is predominantly composed of beta-sheet (47%), which is consistent with its amyloid-like properties. In addition, significant amounts of turn (31%) and alpha-helix (17%) were identified, indicating that amyloid-like fibrils need not be exclusively beta-sheet. The infrared-based secondary structure compositions were then used as constraints to improve the theoretical localization of the secondary structures within PrP-res 27-30.
Insights
Protease-resistant prion protein (PrP-res) aggregates in neurodegenerative diseases. Fourier transform infrared spectroscopy reveals PrP-res 27-30 contains significant beta-sheet, turn, and alpha-helix structures, challenging assumptions about amyloid fibrils.
Area of Science:
- Biochemistry
- Neuroscience
- Structural Biology
Background:
- Protease-resistant prion protein (PrP-res) aggregates in transmissible neurodegenerative diseases like Creutzfeldt-Jakob disease.
- PrP-res forms insoluble amyloid-like fibrils and plaques, identified as key components of scrapie infectivity.
Purpose of the Study:
- To analyze the secondary structure of the proteinase K resistant core of PrP-res (PrP-res 27-30) in infectious fibrils.
- To quantitate secondary structure composition using Fourier transform infrared spectroscopy.
- To inform theoretical models of PrP-res structure.
Main Methods:
- Utilized Fourier transform infrared spectroscopy for protein conformational analysis in aqueous media.
- Applied second-derivative analysis to infrared spectra for secondary structure quantitation.
- Used infrared-derived secondary structure compositions as constraints for theoretical localization.
Main Results:
- PrP-res 27-30 is predominantly beta-sheet (47%), consistent with amyloid properties.
- Significant amounts of turn (31%) and alpha-helix (17%) were identified in PrP-res aggregates.
- Demonstrated that amyloid-like fibrils can contain structures beyond exclusively beta-sheet.
Conclusions:
- PrP-res secondary structure is complex, featuring substantial beta-sheet, turn, and alpha-helix content.
- Findings challenge the notion that amyloid fibrils are solely composed of beta-sheet structures.
- Provides crucial data for refining structural models of PrP-res in prion diseases.