title: When light falls in LOV: a quantum mechanical/molecular mechanical study of photoexcitation in Phot-LOV1 of Chlamydomonas reinhardtii.
abstract: 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 Chlamydomonas 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 dynamic effects mediate signal transmission following the initial photoexcitation event.
authors.affiliation: Beckman Institute, Department of Physics, and Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, 405 North Mathews Avenue, Urbana, Illinois 61801, USA.
authors.forename: Markus
authors.initials: M
authors.lastname: Dittrich
authors.forename: Lydia
authors.initials: L
authors.lastname: Freddolino
authors.forename: Klaus
authors.initials: K
authors.lastname: Schulten
mesh_terms: D000818:Animals; D016825:Chlamydomonas reinhardtii / Q000378:metabolism*; D003545:Cysteine / Q000737:chemistry; D005486:Flavin Mononucleotide / Q000737:chemistry; D008027:Light; D008958:Models, Molecular; D010777:Photochemistry; D010786:Photoreceptor Cells / Q000737:chemistry*; D011789:Quantum Theory
chemical_list: D005486:Flavin Mononucleotide; D003545:Cysteine