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Characterizing the conformational ensemble of monomeric polyglutamine
Xiaoling Wang1, Andreas Vitalis, Matthew A Wyczalkowski
1Department of Biomedical Engineering, Washington University, St. Louis, Missouri 63130, USA.
Proteins
|November 22, 2005
Summary
Polyglutamine peptides aggregate through a disorder-to-order transition. Molecular dynamics simulations reveal that inherent high sidechain amide concentration and diverse solvation modes create an entropy bottleneck, making beta-sheet formation thermodynamically unfavorable.
Area of Science:
- Biochemistry
- Molecular Biology
- Computational Biophysics
Background:
- Polyglutamine (polyQ) peptides are known to aggregate via nucleation and growth.
- Monomeric polyQ peptides, disordered in solution, act as critical nuclei for aggregation.
- The nucleation process involves an unfavorable disorder-to-order transition.
Purpose of the Study:
- Investigate statistical fluctuations driving beta-sheet formation in monomeric polyQ.
- Determine how these fluctuations change with polyQ chain length.
- Explain the thermodynamic basis for the disordered nature of monomeric polyQ.
Main Methods:
- Utilized multiple molecular dynamics (MD) simulations.
- Performed quantitative characterization of conformational ensembles for short polyQ peptides.
- Analyzed peptide disorder, compactness, conformational fluctuations, and solvation modes.
Main Results:
- PolyQ ensembles are inherently disordered, differing from denatured proteins.
- Average compactness and conformational fluctuations increase with polyQ chain length.
- High effective sidechain amide concentration and multiple backbone solvation modes were observed.
Conclusions:
- A conformational entropy bottleneck arises from diverse solvation possibilities.
- This bottleneck makes the thermodynamically unfavorable beta-sheet formation in monomeric polyQ.
- Understanding this mechanism is crucial for polyQ-related disease research.