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Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy
Published on: June 27, 2014
18.6K
Capturing structural intermediates in an animal-like cryptochrome photoreceptor by time-resolved crystallography
Manuel Maestre-Reyna1,2, Yuhei Hosokawa1,2,3, Po-Hsun Wang2,4
1Department of Chemistry, National Taiwan University, 1Roosevelt Rd. Sec. 4, Taipei 106, Taiwan.
Science Advances
|May 16, 2025
Summary
Animal cryptochromes, crucial for circadian rhythms, signal through photoreduction. This study reveals how flavin adenine dinucleotide (FAD) photoreduction and protein unfolding create a signaling state.
Area of Science:
- Biochemistry
- Structural Biology
- Molecular Biology
Background:
- Animal cryptochromes are photoreceptors regulating circadian rhythms and signaling in eukaryotes.
- The signaling mechanism initiated by transient photoreduction of the cryptochrome flavin chromophore is not well understood.
Purpose of the Study:
- To elucidate the photoreduction mechanism of *Chlamydomonas reinhardtii* cryptochrome.
- To provide a structural basis for signaling in animal-like cryptochromes.
Main Methods:
- Serial femtosecond crystallography (SFX) was employed.
- 19 time-resolved SFX snapshots were captured between 10 nanoseconds and 233 milliseconds.
Main Results:
- Cryptochrome photoreduction involves coordinated action at the carboxyl-terminal region, a protonation pathway, and the FAD-binding site.
- Light-driven flavin adenine dinucleotide (FAD) radical pair formation initiates α22 helix unfolding.
- A transient pathway facilitates FAD radical protonation and radical pair stabilization before helix unfolding.
Conclusions:
- The study reveals a mechanism linking radical pair formation to conformational changes in cryptochromes.
- This provides a structural foundation for understanding signaling in animal-like cryptochromes.
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