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Alpha-helix-forming propensities in peptides and proteins
1Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110.
Proteins
|June 1, 1994
Summary
The loss of side chain entropy significantly influences helix formation in peptides and proteins. This study confirms that side chain entropy loss is a primary factor in determining residue helix-forming tendencies.
Area of Science:
- Biophysics
- Computational Biology
- Protein Science
Background:
- Understanding the thermodynamic basis of helix stability in peptides and proteins is crucial.
- Previous studies have measured helix-forming propensities of individual amino acid residues.
Purpose of the Study:
- To test the hypothesis that differences in helix-forming propensity are mainly due to side chain conformational entropy loss upon helix formation.
- To validate previous findings using a more generalized, flexible helix model.
Main Methods:
- Utilized Monte Carlo computer simulations with a flexible helix model.
- Calculated side chain rotamer distributions and entropy losses.
- Compared calculated entropy losses with experimental helix propensity scales.
Main Results:
- Calculated side chain entropy losses using the flexible model agreed with previous results.
- A corrected value for tryptophan (Trp) side chain conformational entropy loss is presented.
- Calculated entropy losses strongly correlated with experimentally derived helix propensity scales from protein helices.
Conclusions:
- Loss of side chain conformational entropy is a major determinant of residue helix-forming tendency.
- This principle applies to both peptide and protein helices.
- Accessible surface area buried upon helix formation showed weak correlation with helix propensity scales.