Electron transfer in cryptochromes and photolyases

Cryptochromes and photolyases are flavoproteins that are found in many vegetal and animal species. Cryptochromes are known to play a role in circadian rhythms, and are also suspected to be involved in magnetic sensing by some bird species. Photolyases are involved in the reparation of DNA damages due to UV light.

DNA-photolyases and cryptochromes are activated under blue-light illumination. This illumination induces an electron transfer that leads to the reduction of the flavin moiety (initialy in its fully oxydized form FAD in cryptochromes). The electron donor is a tryptophan (W324 in Arabidopsis Thaliana cryptochrome) located on the surface of the protein at approximately 15Å of the flavin. The kinetics of this electron transfer is ultra-fast (around 100ns), which can be explained by the presence of two tryptophanes (W400 and W377 in Arabidopsis Thaliana cryptochrome 1) located on the way between FAD and W324. Despite many experimental and theoretical works on cryptochromes, the details of the mechanisms underlying the electron transfer have not been fully elucidated.

Crystallographic structure of Arabidopsis Thaliana cryptochrome 1	Close-up view of the electron transfer chain

This project involves both experimentalists at the CEA Saclay (P. Müller and K. Brettel) and theoreticians (A. de la Lande and F. Cailliez).

Key words

Cryptochromes, electron transfer, Molecular Dynamics, QM/MM

Publications

• "ATP Binding and Aspartate Protonation Enhance Photoinduced Electron Transfer in Plant Cryptochrome". F Cailliez, P Müller, M Gallois, and A de la Lande, J. Am. Chem. Soc., 2014, 136(37):12974-12986.
• "Energetics of Photoinduced Charge Migration within the Tryptophan Tetrad of an Animal (6−4) Photolyase". F Cailliez, P Müller, T Firmino, P Pernot, and A de la Lande, J. Am. Chem. Soc., 2016, 138:1904-1915.