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Folding of prion protein to its native alpha-helical conformation is under kinetic control
I V Baskakov1, G Legname, S B Prusiner
1Institute for Neurodegenerative Diseases, Department of Neurology, University of California, San Francisco, California 94143, USA.
Abstract:
The recombinant mouse prion protein (MoPrP) can be folded either to a monomeric alpha-helical or oligomeric beta-sheet-rich isoform. By using circular dichroism spectroscopy and size-exclusion chromatography, we show that the beta-rich isoform of MoPrP is thermodynamically more stable than the native alpha-helical isoform. The conformational transition from the alpha-helical to beta-rich isoform is separated by a large energetic barrier that is associated with unfolding and with a higher order kinetic process related to oligomerization. Under partially denaturing acidic conditions, MoPrP avoids the kinetic trap posed by the alpha-helical isoform and folds directly to the thermodynamically more stable beta-rich isoform. Our data demonstrate that the folding of the prion protein to its native alpha-helical monomeric conformation is under kinetic control.
Insights
The prion protein
Area of Science:
- Protein folding
- Biochemistry
- Structural biology
Background:
- Prion protein (PrP) misfolding is linked to neurodegenerative diseases.
- Recombinant mouse prion protein (MoPrP) can adopt distinct conformations.
Purpose of the Study:
- To investigate the thermodynamic stability and folding pathways of MoPrP isoforms.
- To understand the kinetic control of prion protein native state formation.
Main Methods:
- Circular dichroism spectroscopy
- Size-exclusion chromatography
- Protein denaturation studies
Main Results:
- The beta-sheet-rich isoform of MoPrP is thermodynamically more stable than the alpha-helical isoform.
- A significant energetic barrier governs the transition between MoPrP isoforms.
- Partially denaturing acidic conditions facilitate direct folding to the stable beta-rich isoform.
Conclusions:
- Prion protein folding to its native alpha-helical conformation is kinetically controlled.
- The native state may represent a kinetic trap, while the beta-rich form is thermodynamically favored.