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Animal-like cryptochromes are photoreceptors that control circadian rhythm and signaling in many eukaryotes. Transient photoreduction of the cryptochrome flavin chromophore initiated signaling via a poorly understood mechanism. By serial femtosecond crystallography (SFX), we show that the photoreduction mechanism of cryptochrome involves three loci [carboxyl-terminal region, a transient protonation pathway, and flavin adenine dinucleotide (FAD)-binding site] acting in unison to accomplish three effects: radical pair stabilization, protonation of FAD radical, and formation of the signaling state. Using 19 time-resolved SFX snapshots between 10 nanoseconds and 233 milliseconds, we found that light-driven FAD/tyrosyl-373 radical pair (RP) formation primes α22 unfolding. Electron transfer-dependent protonation of aspartate-321 by tyrosine-373 is the epicenter of unfolding by disrupting salt bridges between α22 and the photolyase homology region. Before helix unfolding, another pathway opens transiently for FAD protonation and RP stabilization. This link between RP formation and conformational changes provides a structural basis for signaling by animal-like cryptochromes.
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http://dx.doi.org/10.1126/sciadv.adu7247 | DOI Listing |
J Phys Chem Lett
June 2025
Center for Ultrafast Science and Technology, School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
The significance of the photoreduction channel via the tryptophan triad in the cryptochrome (CRY) has been generally recognized. However, there is literature reporting the retention of biological function in the primary electron transfer (ET) pathway-impaired mutants in some CRY species. In this work, a secondary ET pathway is identified in the animal-like cryptochrome (aCRY) in the opposite direction of the primary ET pathway, involving ultrafast electron tunneling and proton transfer.
View Article and Find Full Text PDFSci Adv
May 2025
Department of Chemistry, Philipps University Marburg, Hans-Meerwein Strasse 4, Marburg 35032, Germany.
Animal-like cryptochromes are photoreceptors that control circadian rhythm and signaling in many eukaryotes. Transient photoreduction of the cryptochrome flavin chromophore initiated signaling via a poorly understood mechanism. By serial femtosecond crystallography (SFX), we show that the photoreduction mechanism of cryptochrome involves three loci [carboxyl-terminal region, a transient protonation pathway, and flavin adenine dinucleotide (FAD)-binding site] acting in unison to accomplish three effects: radical pair stabilization, protonation of FAD radical, and formation of the signaling state.
View Article and Find Full Text PDFJ Am Chem Soc
May 2024
Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt Max-von-Laue-Str. 9, 60438 Frankfurt/Main, Germany.
Many biological mechanisms rely on the precise control of conformational changes in proteins. Understanding such dynamic processes requires methods for determining structures and their temporal evolution. In this study, we introduce a novel approach to time-resolved ion mobility mass spectrometry.
View Article and Find Full Text PDFSci Rep
October 2023
Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka, 560-8531, Japan.
An animal-like cryptochrome derived from Chlamydomonas reinhardtii (CraCRY) is a bifunctional flavoenzyme harboring flavin adenine dinucleotide (FAD) as a photoreceptive/catalytic center and functions both in the regulation of gene transcription and the repair of UV-induced DNA lesions in a light-dependent manner, using different FAD redox states. To address how CraCRY stabilizes the physiologically relevant redox state of FAD, we investigated the thermodynamic and kinetic stability of the two-electron reduced anionic FAD state (FADH) in CraCRY and related (6-4) photolyases. The thermodynamic stability of FADH remained almost the same compared to that of all tested proteins.
View Article and Find Full Text PDFCommun Biol
October 2022
State Key Laboratory of Surface Physics, Department of Physics, Fudan University, 200433, Shanghai, China.
Cryptochromes are blue light receptors that mediate circadian rhythm and magnetic sensing in various organisms. A typical cryptochrome consists of a conserved photolyase homology region domain and a varying carboxyl-terminal extension across species. The structure of the flexible carboxyl-terminal extension and how carboxyl-terminal extension participates in cryptochrome's signaling function remain mostly unknown.
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