title: Crystal structures and molecular mechanism of a light-induced signaling switch: The Phot-LOV1 domain from Chlamydomonas reinhardtii.
abstract: Phot proteins (phototropins and homologs) are blue-light photoreceptors that control mechanical processes like phototropism, chloroplast relocation, or guard-cell opening in plants. Phot receptors consist of two flavin mononucleotide (FMN)-binding light, oxygen, or voltage (LOV) domains and a C-terminal serine/threonine kinase domain. We determined crystal structures of the LOV1 domain of Phot1 from the green alga Chlamydomonas reinhardtii in the dark and illuminated state to 1.9 A and 2.8 A resolution, respectively. The structure resembles that of LOV2 from Adiantum (Crosson, S. and K. Moffat. 2001. PROC: Natl. Acad. Sci. USA. 98:2995-3000). In the resting dark state of LOV1, the reactive Cys-57 is present in two conformations. Blue-light absorption causes formation of a proposed active signaling state that is characterized by a covalent bond between the flavin C4a and the thiol of Cys-57. There are differences around the FMN chromophore but no large overall conformational changes. Quantum chemical calculations based on the crystal structures revealed the electronic distribution in the active site during the photocycle. The results suggest trajectories for electrons, protons, and the active site cysteine and offer an interpretation of the reaction mechanism.
authors.affiliation: Max Planck Institut für Molekulare Physiologie, Abteilung Biophysikalische Chemie, 44227 Dortmund, Germany.
authors.forename: Roman
authors.initials: R
authors.lastname: Fedorov
authors.forename: Ilme
authors.initials: I
authors.lastname: Schlichting
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Hartmann
authors.forename: Tatjana
authors.initials: T
authors.lastname: Domratcheva
authors.forename: Markus
authors.initials: M
authors.lastname: Fuhrmann
authors.forename: Peter
authors.initials: P
authors.lastname: Hegemann
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000528:radiation effects*; D016825:Chlamydomonas reinhardtii / Q000737:chemistry; D003198:Computer Simulation; D003461:Crystallography / Q000379:methods*; D003624:Darkness; D008027:Light; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000737:chemistry* / Q000528:radiation effects*; D011487:Protein Conformation; D017346:Protein Serine-Threonine Kinases; D017434:Protein Structure, Tertiary; D013329:Structure-Activity Relationship
chemical_list: D029681:Arabidopsis Proteins; D010750:Phosphoproteins; C103646:NPH1 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases