title: Light-Induced Rearrangement of the β5 Strand in the BLUF Photoreceptor SyPixD (Slr1694).
abstract: The structural changes that facilitate signal transduction in blue light sensors using FAD (BLUF) photoreceptors and confer the stability of the rearranged hydrogen bond network between flavin and protein in the signaling state are still poorly understood. Here, we investigate a semiconserved Trp residue in SyPixD (Slr1694) by isotope-edited vibrational spectroscopy and site-directed mutagenesis. In the signaling state, a β-sheet structure involving the backbone of W91 is formed without apparent change of environment of the W91 indole side chain. Mutation of W91, however, significantly influences the stability of the light-adapted state, suggesting that backbone rigidity rather than discrete side-chain conformations govern the stability of the light-adapted state. On the basis of computational and crystallographic models, we interpret these changes as a +1 register shift of the β2/β5 interaction with an unaffected indole side-chain conformation, rather than a +2 register shift accompanied by an indole side-chain flip that was previously proposed on the basis of X-ray structures.
authors.affiliation: Department of Biology, Experimental Biophysics, Humboldt-Universität zu Berlin , Invalidenstraße 42, 10115 Berlin, Germany.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Mehlhorn
authors.affiliation: Department of Biology, Experimental Biophysics, Humboldt-Universität zu Berlin , Invalidenstraße 42, 10115 Berlin, Germany.
authors.forename: Tom
authors.initials: T
authors.lastname: Lindtner
authors.affiliation: Department of Biology, Experimental Biophysics, Humboldt-Universität zu Berlin , Invalidenstraße 42, 10115 Berlin, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Richter
authors.affiliation: Department of Biology, Experimental Biophysics, Humboldt-Universität zu Berlin , Invalidenstraße 42, 10115 Berlin, Germany.
authors.forename: Kathrin
authors.initials: K
authors.lastname: Glass
authors.affiliation: Department of Biology, Experimental Biophysics, Humboldt-Universität zu Berlin , Invalidenstraße 42, 10115 Berlin, Germany.
authors.forename: Helena
authors.initials: H
authors.lastname: Steinocher
authors.affiliation: Department of Chemistry, Humboldt-Universität zu Berlin , Brook-Taylor-Str. 2, 12489 Berlin, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Beck
authors.affiliation: Department of Biology, Experimental Biophysics, Humboldt-Universität zu Berlin , Invalidenstraße 42, 10115 Berlin, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Hegemann
authors.affiliation: Department of Physics and Astronomy, Biophysics Section, Faculty of Sciences, Vrije Universiteit , De Boelelaan 1081, 1081 HV, Amsterdam, The Netherlands.
authors.forename: John T M
authors.initials: JT
authors.lastname: Kennis
authors.affiliation: Department of Biology, Experimental Biophysics, Humboldt-Universität zu Berlin , Invalidenstraße 42, 10115 Berlin, Germany.|Department of Physics and Astronomy, Biophysics Section, Faculty of Sciences, Vrije Universiteit , De Boelelaan 1081, 1081 HV, Amsterdam, The Netherlands.
authors.forename: Tilo
authors.initials: T
authors.lastname: Mathes
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D005415:Flavins / Q000737:chemistry*; D008027:Light; D020283:Photoreceptors, Microbial / Q000737:chemistry*; D011485:Protein Binding; D017510:Protein Folding; D015398:Signal Transduction; D014364:Tryptophan / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; D005415:Flavins; D020283:Photoreceptors, Microbial; D014364:Tryptophan
keywords: FTIR; flavin; isotope labeling; signal transduction; tryptophan