Underexposed polar residues and protein stabilization
Sara Ayuso-Tejedor1, Olga Abián, Javier Sancho
1Departamento de Bioquímica y Biología Molecular y Celular, Facultad de Ciencias, Universidad de Zaragoza, Zaragoza 50009, Spain.
Protein Engineering, Design & Selection : PEDS
|October 13, 2010
Summary
Replacing polar protein residues with apolar ones can increase stability. Glutamine to Leucine (Q → L) mutations show promise for enhancing protein stability by optimizing burial of residues.
Area of Science:
- Biochemistry
- Protein Engineering
- Computational Biology
Background:
- Protein stability is crucial for practical applications and understanding fundamental energetics.
- Modifying protein stability offers insights into protein folding and energetic principles.
- Investigating residue substitutions is key to protein design and engineering.
Purpose of the Study:
- To explore the feasibility of stabilizing proteins by substituting underexposed polar residues with similar-sized apolar ones.
- To compare the stability of wild-type apoflavodoxin with selected mutants.
- To analyze the relationship between residue burial and protein stability.
Main Methods:
- Site-directed mutagenesis of apoflavodoxin to introduce specific amino acid substitutions (Y → F, Q → L, T → V, K → M).
- Experimental determination of mutant protein stability.
- Analysis of published stability data for various mutant proteins.
- Development of predictive equations based on differential polar and apolar burial.
Main Results:
- Most mutations did not significantly increase protein stability, despite an inverse correlation between native polar residue exposure and mutant stability.
- Glutamine to Leucine (Q → L) mutations were exceptions, showing the greatest reduction in polar burial and increase in apolar burial, leading to enhanced stability.
- Published data and new predictive models suggest Q → L and potentially N → L mutations are stabilizing.
- Stability changes were rationalized by differential polar/apolar burial upon folding and a generic destabilizing penalty term.
Conclusions:
- Strategic substitution of specific polar residues with apolar ones, particularly Glutamine to Leucine (Q → L), can enhance protein stability.
- Predictive models based on burial energetics offer a simplified yet effective approach to forecasting stability changes in mutants.
- This study provides valuable insights into protein design principles for engineering more stable proteins.
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