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Thermodynamic analysis of a designed three-stranded coiled coil
J A Boice1, G R Dieckmann, W F DeGrado
1Bristol-Myers Squibb Pharmaceutical Research Institute, Princeton, New Jersey 08543-4000, USA.
Biochemistry
|November 19, 1996
Summary
Researchers designed a stable trimeric coiled coil protein using specific amino acid placements. This protein oligomerization follows a cooperative equilibrium, revealing key thermodynamic rules for protein folding and stability.
Area of Science:
- Protein biochemistry
- Biophysical chemistry
- Structural biology
Background:
- Coiled-coil protein structural motifs offer insights into protein folding and stability.
- Understanding the rules governing specific oligomerization is crucial for protein design.
Purpose of the Study:
- To quantitatively determine the rules governing coiled-coil oligomerization using a thermodynamic approach.
- To design and characterize a highly stable trimeric coiled coil.
Main Methods:
- Design of a trimeric coiled coil with valine at 'a' positions and leucine at 'd' positions.
- Sedimentation equilibrium to determine trimer stability.
- Circular dichroism spectroscopy to study oligomerization equilibrium.
- Guanidinium chloride denaturation and thermal unfolding analysis to quantify thermodynamic parameters.
Main Results:
- A highly stable trimeric coiled coil was successfully designed.
- Oligomerization follows a cooperative monomer/dimer/trimer equilibrium with an unstable dimer intermediate.
- Free energy of stabilization for the trimer is -18.4 kcal mol⁻¹.
- Heat capacity (ΔCp) of 750 cal deg⁻¹ mol⁻¹ (8.6 cal deg⁻¹ mol⁻¹ per residue) was determined, indicating a well-defined tertiary structure.
Conclusions:
- The designed coiled coil exhibits remarkable stability and cooperative trimerization.
- The study quantifies thermodynamic rules essential for coiled-coil protein folding and stability.
- The findings contribute to the rational design of protein structures with specific oligomerization states.