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Updated: Jul 18, 2026

Sedimentation Equilibrium of a Small Oligomer-forming Membrane Protein: Effect of Histidine Protonation on Pentameric Stability
Published on: April 2, 2015
Electrostatic contributions to residue-specific protonation equilibria and proton binding capacitance for a small
Stina Lindman1, Sara Linse, Frans A A Mulder
1Department of Biophysical Chemistry, Lund University, Chemical Center, SE-22100 Lund, Sweden. stina.lindman@bpc.lu.se
Protein charge interactions influence biological processes. Using carbon-13 NMR chemical shifts, researchers precisely measured protonation equilibria in a protein variant, revealing insights into local charge effects on protein electrostatics.
Area of Science:
- Biochemistry
- Structural Biology
- Biophysics
Background:
- Charge-charge interactions are fundamental to protein function.
- Understanding site-specific protonation is crucial for protein electrostatics.
Purpose of the Study:
- To detect site-specific protonation equilibria in a protein variant using 13C NMR.
- To analyze local charge-charge interactions and electrostatic coupling within proteins.
Main Methods:
- Utilized 13C NMR chemical shift data from aspartate and glutamate side chains.
- Analyzed protonation equilibria and titration curves.
- Applied Coulomb's law for electrostatic interaction calculations.
Main Results:
- Detected site-specific protonation equilibria with high precision.
- Observed that local charge interactions skew ideal titration curves.
- Found that self-energy differences, not direct charge-charge interactions, primarily shift pKa values in the PGB1-QDD variant.
Conclusions:
- Developed a framework for analyzing convoluted titration data to study electrostatic coupling.
- Demonstrated that protein environment significantly influences proton binding affinity.
- Highlighted the importance of self-energy in protein pKa shifts.
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