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Published on: June 21, 2021
Redox-active tyrosine residues in pentapeptides
Ilya R Vassiliev1, Adam R Offenbacher, Bridgette A Barry
1School of Chemistry and Biochemistry and Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332-0363, USA.
The Journal of Physical Chemistry. B
|July 21, 2006
Summary
Protein sequence significantly impacts tyrosyl radical properties, influencing electron transfer in enzymes. This study reveals sequence-dependent alterations in tyrosyl radicals, affecting their spectroscopic and electronic characteristics.
Area of Science:
- Biochemistry
- Spectroscopy
- Enzyme mechanisms
Background:
- Tyrosyl radicals are crucial for long-range electron transfer in enzymes like ribonucleotide reductase and photosystem II.
- Understanding protein environmental effects on tyrosyl radical midpoint potential and electron transfer rates is limited.
Purpose of the Study:
- Investigate the influence of protein sequence on the photophysical properties of tyrosyl radicals.
- Elucidate the relationship between peptide sequence and tyrosyl radical behavior.
Main Methods:
- Studied spectroscopic properties of tyrosyl radicals generated by UV-photolysis of pentapeptides at 85 K.
- Utilized Electron Paramagnetic Resonance (EPR) and Fourier Transform Infrared (FT-IR) spectroscopy.
- Designed pentapeptide sequences to mimic those in redox-active tyrosine enzymes.
Main Results:
- EPR line shape of tyrosyl radicals demonstrated sequence-dependent variations.
- Observed a transient EPR signal component decaying on the second timescale at 85 K, attributed to conformational rearrangement.
- FT-IR spectra showed sequence-dependent alterations in amide I and peptide bond skeletal vibrations.
- Provided evidence for spin delocalization from the tyrosine ring into the peptide bond.
Conclusions:
- Primary protein structure influences the functional properties of redox-active tyrosines.
- Oxidation of the tyrosine ring perturbs the electronic structure of the peptide bond.
- Sequence-dependent effects are likely mediated by electrostatics or conformational preferences.
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