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Osmolyte-induced changes in protein conformational equilibria
A J Saunders1, P R Davis-Searles, D L Allen
1Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
Biopolymers
|February 24, 2000
Summary
Osmolytes stabilize protein structures by influencing conformational equilibria. Excluded volume effects are the main drivers, with binding interactions playing a secondary role in protein stability.
Area of Science:
- Biochemistry
- Biophysics
- Protein Science
Background:
- Solute-induced changes in protein conformational equilibria are key to understanding protein stability.
- The molecular mechanisms behind these solute effects are debated.
- Yeast iso-1-ferricytochrome c serves as a model system.
Purpose of the Study:
- To investigate osmolyte-induced changes in the stability of yeast iso-1-ferricytochrome c.
- To elucidate the molecular contributions of excluded volume and binding interactions to protein stabilization.
Main Methods:
- Experimental analysis of cytochrome c stability in the presence of polyol osmolytes.
- Theoretical calculations using Scaled Particle Theory (SPT).
- Decomposition of free energy into steric repulsion and binding interaction components.
Main Results:
- Polyol osmolytes induce specific conformational states (A and N) from denatured cytochrome c.
- Protein stability increases linearly with osmolyte concentration.
- The A state is stabilized more than the N state by osmolytes.
Conclusions:
- Excluded volume effects are the primary mechanism for osmolyte-induced protein stabilization.
- Changes in water-protein and osmolyte-protein binding interactions contribute differentially to the stability of different protein states.
- Findings reconcile experimental data with theoretical interpretations of solute effects on protein conformation.