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Structural parameters controlling the fluorescence properties of phytochromes
Francisco Velazquez Escobar1, Thomas Hildebrandt, Tillmann Utesch
1Technische Universität Berlin , Institut für Chemie, Sekr. PC14, Straße des 17. Juni 135, D-10623 Berlin, Germany.
Biochemistry
|December 17, 2013
Summary
Engineered phytochromes (iRFP) show enhanced fluorescence for deep tissue imaging. Structural changes in the chromophore pocket reduce non-radiative decay, increasing fluorescence quantum yields.
Area of Science:
- Photochemistry
- Biophysics
- Spectroscopy
Background:
- Phytochromes are photoreceptors with a tetrapyrrole chromophore absorbing red light.
- Their low fluorescence quantum yields limit deep tissue imaging applications.
- Engineering phytochrome variants with higher fluorescence is of significant interest.
Purpose of the Study:
- To understand structural parameters controlling phytochrome photophysical properties.
- To elucidate chromophore structural changes in a fluorescence-optimized mutant (iRFP).
Main Methods:
- Resonance Raman (RR) spectroscopy
- Molecular dynamics simulations
- Studied the PAS-GAF domain of bacteriophytochrome RpBphP2
Main Results:
- Identified structural changes in the iRFP mutant compared to wild-type.
- Increased tilt angle of terminal ring D and reduced hydrogen bonding in iRFP.
- Decreased chromophore flexibility, particularly in rings D and A, in iRFP.
Conclusions:
- Structural modifications in iRFP lower the probability of non-radiative excited state decays.
- These changes account for the enhanced fluorescence properties of the engineered phytochrome.
- Findings provide insights for designing improved fluorescent protein probes.
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