title: Femtosecond to Millisecond Dynamics of Light Induced Allostery in the Avena sativa LOV Domain.
abstract: The rational engineering of photosensor proteins underpins the field of optogenetics, in which light is used for spatiotemporal control of cell signaling. Optogenetic elements function by converting electronic excitation of an embedded chromophore into structural changes on the microseconds to seconds time scale, which then modulate the activity of output domains responsible for biological signaling. Using time-resolved vibrational spectroscopy coupled with isotope labeling, we have mapped the structural evolution of the LOV2 domain of the flavin binding phototropin Avena sativa (AsLOV2) over 10 decades of time, reporting structural dynamics between 100 fs and 1 ms after optical excitation. The transient vibrational spectra contain contributions from both the flavin chromophore and the surrounding protein matrix. These contributions are resolved and assigned through the study of four different isotopically labeled samples. High signal-to-noise data permit the detailed analysis of kinetics associated with the light activated structural evolution. A pathway for the photocycle consistent with the data is proposed. The earliest events occur in the flavin binding pocket, where a subpicosecond perturbation of the protein matrix occurs. In this perturbed environment, the previously characterized reaction between triplet state isoalloxazine and an adjacent cysteine leads to formation of the adduct state; this step is shown to exhibit dispersive kinetics. This reaction promotes coupling of the optical excitation to successive time-dependent structural changes, initially in the β-sheet and then α-helix regions of the AsLOV2 domain, which ultimately gives rise to Jα-helix unfolding, yielding the signaling state. This model is tested through point mutagenesis, elucidating in particular the key mediating role played by Q513.
authors.affiliation: Department of Chemistry, Stony Brook University , New York 11794-3400, United States.
authors.forename: Agnieszka A
authors.initials: AA
authors.lastname: Gil
authors.affiliation: School of Chemistry, University of East Anglia , Norwich, NR4 7TJ, U.K.
authors.forename: Sergey P
authors.initials: SP
authors.lastname: Laptenok
authors.affiliation: Department of Chemistry, Stony Brook University , New York 11794-3400, United States.
authors.forename: Jarrod B
authors.identifier: 0000-0002-6762-1309
authors.initials: JB
authors.lastname: French
authors.affiliation: Department of Chemistry, Stony Brook University , New York 11794-3400, United States.
authors.forename: James N
authors.initials: JN
authors.lastname: Iuliano
authors.affiliation: School of Chemistry, University of East Anglia , Norwich, NR4 7TJ, U.K.|Department of Biophysics, Medical School, University of Pecs , Szigeti ut 12, 7624 Pecs, Hungary.
authors.forename: Andras
authors.initials: A
authors.lastname: Lukacs
authors.affiliation: School of Chemistry, University of East Anglia , Norwich, NR4 7TJ, U.K.
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Hall
authors.affiliation: Central Laser Facility, Research Complex at Harwell, Rutherford Appleton Laboratory , Didcot, Oxon OX11 0QX, U.K.
authors.forename: Igor V
authors.initials: IV
authors.lastname: Sazanovich
authors.affiliation: Central Laser Facility, Research Complex at Harwell, Rutherford Appleton Laboratory , Didcot, Oxon OX11 0QX, U.K.
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Greetham
authors.affiliation: Department Chemie, Technische Universität München , D-85747 Garching, Germany.
authors.forename: Adelbert
authors.initials: A
authors.lastname: Bacher
authors.affiliation: Institut für Biochemie und Lebensmittelchemie, Universität Hamburg , Grindelallee 117, D-20146 Hamburg, Germany.
authors.forename: Boris
authors.initials: B
authors.lastname: Illarionov
authors.affiliation: Institut für Biochemie und Lebensmittelchemie, Universität Hamburg , Grindelallee 117, D-20146 Hamburg, Germany.
authors.forename: Markus
authors.identifier: 0000-0001-7243-4199
authors.initials: M
authors.lastname: Fischer
authors.affiliation: Department of Chemistry, Stony Brook University , New York 11794-3400, United States.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Tonge
authors.affiliation: School of Chemistry, University of East Anglia , Norwich, NR4 7TJ, U.K.
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Meech
mesh_terms: D000494:Allosteric Regulation; D018554:Avena / Q000737:chemistry* / Q000528:radiation effects*; D007700:Kinetics; D008027:Light; D008958:Models, Molecular; D055095:Optics and Photonics; D056949:Phototropins / Q000235:genetics / Q000378:metabolism; D000072417:Protein Domains / Q000528:radiation effects; D013057:Spectrum Analysis
chemical_list: D056949:Phototropins