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Probing electrostatic interactions and structural changes in highly charged protein polyanions by conformer-selective
Matthias Vonderach1, Oli T Ehrler, Katerina Matheis
1Institut für Physikalische Chemie, Karlsruhe Institute of Technology (KIT), D-76131 Karlsruhe, Germany.
Physical Chemistry Chemical Physics : PCCP
|August 2, 2011
Summary
Researchers captured the first conformer-selective photoelectron spectra of protein polyanions. This study reveals how increasing negative charges induce structural changes, transitioning bovine cytochrome c from folded to unfolded states.
Area of Science:
- Physical Chemistry
- Biophysics
- Spectroscopy
Background:
- Proteins carry biological information through their complex structures.
- Understanding protein conformational changes is crucial for molecular biology.
- Polyanions are proteins with multiple negative charges.
Purpose of the Study:
- To investigate the gas-phase conformational dynamics of protein polyanions.
- To measure electron binding energies and probe intramolecular Coulomb repulsion.
- To determine the charge state at which protein unfolding occurs.
Main Methods:
- Conformer-selective photoelectron spectroscopy of bovine cytochrome c.
- Studying protein in 8 negative charge states (5- to 12-).
- Ion-mobility measurements and electrostatic modeling.
Main Results:
- First conformer-selective photoelectron spectra of a protein polyanion obtained.
- Electron binding energies directly correlated with intramolecular Coulomb repulsion.
- A structural transition from folded to unfolded states observed with increasing negative charges.
- Unfolding onset identified at the 6- charge state, revealing three distinct conformers.
Conclusions:
- A simple electrostatic model accurately reproduces experimental findings.
- Protein polyanion structure is sensitive to charge state.
- Ion mobility data pinpoint the critical charge for conformational transition.
