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Thermodynamics of Membrane Protein Folding Measured by Fluorescence Spectroscopy
Published on: April 28, 2011
Conformational properties of unfolded HypF-N
Yujie Chen1, Claudia Parrini, Niccolò Taddei
1Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA.
The Journal of Physical Chemistry. B
|November 26, 2009
Summary
Intramolecular diffusion in the aggregation-prone HypF-N protein is constant at high denaturant levels but slows unevenly at lower levels. This suggests partially unfolded protein states are prone to aggregation.
Area of Science:
- Biochemistry
- Protein Dynamics
- Biophysics
Background:
- Protein aggregation is implicated in various diseases.
- Understanding protein folding and unfolding dynamics is crucial for comprehending aggregation.
- The HypF-N protein fragment is known to be aggregation-prone.
Purpose of the Study:
- To measure the intramolecular diffusion rate in the aggregation-prone HypF-N protein.
- To investigate how denaturant concentration affects protein chain dynamics.
- To correlate protein dynamics with aggregation propensity.
Main Methods:
- Utilized cysteine quenching of the tryptophan triplet state.
- Measured intramolecular diffusion rates under varying concentrations of guanidinium chloride (GdnHCl).
- Extrapolated diffusion rates to zero denaturant concentration.
Main Results:
- Intramolecular diffusion remained constant at high denaturant concentrations (2-6 M GdnHCl).
- Diffusion slowed down at lower denaturant concentrations, with non-uniform changes along the protein chain.
- Extrapolated diffusion rate at 0 M GdnHCl was approximately 10(-7) cm(2) s(-1).
- This rate is significantly higher than well-behaved proteins but lower than unstructured peptides.
Conclusions:
- Partially unfolded protein states exhibit a dynamic range of conformational reorganization.
- This dynamic range contributes to the propensity of these states to aggregate.
- Protein dynamics play a critical role in aggregation-prone states.
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