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Mechanistic Models Fit to Variable Temperature Calorimetric Data Provide Insights into Cooperativity
Elihu C Ihms1, Ian R Kleckner1, Paul Gollnick2
1Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio.
Biophysical Journal
|April 14, 2017
Summary
Understanding allostery requires detailed thermodynamic analysis. This study uses temperature-dependent calorimetry and statistical models to quantify ligand binding thermodynamics in the trp RNA-binding Attenuation Protein, revealing microscopic contributions to cooperativity.
Area of Science:
- Biochemistry
- Biophysics
- Structural Biology
Background:
- Allostery is crucial for macromolecular function, involving cooperative ligand binding.
- Interpreting allosteric mechanisms is challenging due to dynamic conformational changes (microstates).
- Isothermal titration calorimetry (ITC) quantifies binding thermodynamics but often lacks mechanistic detail.
Purpose of the Study:
- To decipher the microscopic mechanisms of cooperative ligand binding.
- To overcome limitations of conventional ITC data analysis for allosteric systems.
- To quantify the thermodynamic contributions of individual ligand interactions.
Main Methods:
- Global fitting of temperature-dependent isothermal titration calorimetry data.
- Application of nearest-neighbor statistical thermodynamic models.
- Analysis of 11 tryptophan ligand binding to the trp RNA-binding Attenuation Protein.
Main Results:
- Distinguished between alternative nearest-neighbor interaction models.
- Quantified the thermodynamic contribution of neighboring ligands to individual binding sites.
- Demonstrated the limitations of conventional Hill equation modeling for mechanistic insight.
Conclusions:
- Mechanistically constrained global fitting of binding data can yield essential microscopic thermodynamic parameters.
- This approach is valuable for deciphering cooperativity mechanisms in ligand-regulated homo-oligomeric assemblies.
- Highlights the potential of advanced thermodynamic modeling for understanding complex biological systems.