Related Experiment Videos
Amyloid fibrils from the mammalian protein prothymosin alpha
Nikolai A Pavlov1, Dmitry I Cherny, Gudrun Heim
1Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.
Abstract:
Mammalian prothymosin alpha, a small (12 kDa) and extremely acidic protein (pI 3.5), is a member of the growing family of 'natively' unfolded proteins. We demonstrate that at low pH ( approximately 3) and high concentrations, prothymosin alpha is capable of forming regular elongated fibrils with flat ribbon structure 4-5 nm in height and 12-13 nm in width as judged from scanning force and electron microscopy. These aggregates induced a characteristic spectral shift of thioflavin T fluorescence and their circular dichroism spectra were indicative of significant beta-sheet content, suggesting formation of classical amyloid. Our findings indicate that natively unfolded proteins may have a general propensity to form amyloid fibrils under conditions inducing partially folded conformations.
Insights
Mammalian prothymosin alpha, a natively unfolded protein, forms amyloid fibrils under specific low pH and high concentration conditions. This suggests a general tendency for such proteins to aggregate into amyloid structures when partially folded.
Area of Science:
- Biochemistry
- Structural Biology
- Protein Chemistry
Background:
- Prothymosin alpha is a small, acidic, natively unfolded protein.
- Natively unfolded proteins lack stable tertiary structures under physiological conditions.
Purpose of the Study:
- To investigate the aggregation behavior of mammalian prothymosin alpha.
- To determine if natively unfolded proteins can form amyloid structures.
Main Methods:
- Scanning force microscopy
- Electron microscopy
- Thioflavin T fluorescence assay
- Circular dichroism spectroscopy
Main Results:
- Prothymosin alpha formed elongated fibrils (4-5 nm height, 12-13 nm width) at low pH and high concentrations.
- These fibrils exhibited spectral shifts with Thioflavin T, indicating amyloid formation.
- Circular dichroism spectra revealed significant beta-sheet content in the aggregates.
Conclusions:
- Natively unfolded proteins, like prothymosin alpha, can form classical amyloid fibrils.
- Partially folded conformations induced by specific conditions promote amyloid formation in these proteins.