Markus Dittrich, Peter L. Freddolino, and Klaus Schulten. When light falls in LOV: A quantum mechanical/molecular mechanical study of photoexcitation in Phot-LOV1 of Chlamydomonas reinhardtii. Journal of Physical Chemistry B, 109:13006-13013, 2005. (PMC: 2453334)

DITT2005 Plants use sophisticated photosensing mechanisms to maximize their utilization of the available sunlight and to control developmental processes. The plant blue-light receptors of the phot family mediate plant phototropism and contain two light, oxygen, and voltage (LOV) sensitive domains as photoactive elements. Here, we report combined quantum mechanical/molecular mechanical simulations of the photocycle of a complete Phot-LOV1 domain from C. reinhardtii. We have investigated the electronic properties and structural changes that follow blue-light absorption. This permitted us to characterize the pathway for flavin-cysteinyl adduct formation, which was found to proceed via a neutral radical state generated by hydrogen atom transfer from the reactive cysteine residue, Cys57, to the chromophore flavin mononucleotide. Interestingly, we find that adduct formation does not cause any larger scale conformational changes in Phot-LOV1 which suggests that dynamical effects mediate signal transmission following the initial photoexcitation event.


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