Direct Measurement of Charge Regulation in Metalloprotein Electron Transfer

Angewandte Chemie
Collin T ZahlerBryan F Shaw

Abstract

Determining whether a protein regulates its net electrostatic charge during electron transfer (ET) will deepen our mechanistic understanding of how polypeptides tune rates and free energies of ET (e.g., by affecting reorganization energy, and/or redox potential). Charge regulation during ET has never been measured for proteins because few tools exist to measure the net charge of a folded protein in solution at different oxidation states. Herein, we used a niche analytical tool (protein charge ladders analyzed with capillary electrophoresis) to determine that the net charges of myoglobin, cytochrome c, and azurin change by 0.62±0.06, 1.19±0.02, and 0.51±0.04 units upon single ET. Computational analysis predicts that these fluctuations in charge arise from changes in the pKa  values of multiple non-coordinating residues (predominantly histidine) that involve between 0.42-0.90 eV. These results suggest that ionizable residues can tune the reactivity of redox centers by regulating the net charge of the entire protein-cofactor-solvent complex.

References

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Citations

Feb 20, 2019·Chemistry : a European Journal·Collin T Zahler, Bryan F Shaw
Mar 27, 2020·Angewandte Chemie·Ao Yun ZhangBryan F Shaw

Methods Mentioned

BETA
electrophoresis
acetylation

Related Concepts

Azurin
Respiratory Chain
Hydrogen-Ion Concentration
Metalloproteins
Myoglobin
Oxidation-Reduction
Thermodynamics
Apocytochrome C
Static Electricity
Cytochromes c

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