Decrypting Cryptochrome: Revealing the Molecular Identity of the Photoactivation Reaction

Ilia A. Solov'yov, Tatiana Domratcheva, Abdul Rehaman Moughal Shahi, Klaus Schulten
Journal of the American Chemical Society
134
18046-18052
2012
abstract
Migrating birds fly thousand miles and more, often without visual cues and in treacherous winds, yet keep direction. They employ for this purpose, apparently, as a powerful navigational tool the photoreceptor protein cryptochrome to sense the geomagnetic field. The unique biological function of cryptochrome must arise from the photoactivation reaction occurring in the protein: exposure to blue light results in electron transfer to a flavin pigment co-factor, leading to formation of an electron spin-entangled pair of radicals. Theoretical and experimental studies established long ago that such radical pairs, indeed, can act as a magnetic compass. The photo-reaction pathway in cryptochrome is not fully resolved yet. We employ ab initio quantum chemistry and classical all-atom MD simulations for Arabidopsis thaliana cryptochrome to determine how the radical pair is formed, becomes stabilized through proton transfer, and how it decays back to the protein's resting state.
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Paper selected for a cover and for a JACS Spotlight