title: Intersubunit distances in full-length, dimeric, bacterial phytochrome Agp1, as measured by pulsed electron-electron double resonance (PELDOR) between different spin label positions, remain unchanged upon photoconversion.
abstract: Bacterial phytochromes are dimeric light-regulated histidine kinases that convert red light into signaling events. Light absorption by the N-terminal photosensory core module (PCM) causes the proteins to switch between two spectrally distinct forms, Pr and Pfr, thus resulting in a conformational change that modulates the C-terminal histidine kinase region. To provide further insights into structural details of photoactivation, we investigated the full-length Agp1 bacteriophytochrome from the soil bacteriumAgrobacterium fabrumusing a combined spectroscopic and modeling approach. We generated seven mutants suitable for spin labeling to enable application of pulsed EPR techniques. The distances between attached spin labels were measured using pulsed electron-electron double resonance spectroscopy to probe the arrangement of the subunits within the dimer. We found very good agreement of experimental and calculated distances for the histidine-kinase region when both subunits are in a parallel orientation. However, experimental distance distributions surprisingly showed only limited agreement with either parallel- or antiparallel-arranged dimer structures when spin labels were placed into the PCM region. This observation indicates that the arrangements of the PCM subunits in the full-length protein dimer in solution differ significantly from that in the PCM crystals. The pulsed electron-electron double resonance data presented here revealed either no or only minor changes of distance distributions upon Pr-to-Pfr photoconversion.
authors.affiliation: From the Albert-Ludwigs-Universität Freiburg, Institut für Physikalische Chemie, 79104 Freiburg, Germany, Sylwia.Kacprzak@physchem.uni-freiburg.de.
authors.forename: Sylwia
authors.initials: S
authors.lastname: Kacprzak
authors.affiliation: the Karlsruhe Institute of Technology, Botanical Institute I, 76131 Karlsruhe, Germany.
authors.forename: Ibrahim
authors.initials: I
authors.lastname: Njimona
authors.affiliation: From the Albert-Ludwigs-Universität Freiburg, Institut für Physikalische Chemie, 79104 Freiburg, Germany.
authors.forename: Anja
authors.initials: A
authors.lastname: Renz
authors.affiliation: the Karlsruhe Institute of Technology, Botanical Institute I, 76131 Karlsruhe, Germany.
authors.forename: Juan
authors.initials: J
authors.lastname: Feng
authors.affiliation: the Max Planck Institute for Chemical Energy Conversion, 45470 Mülheim an der Ruhr, Germany.
authors.forename: Edward
authors.initials: E
authors.lastname: Reijerse
authors.affiliation: the Max Planck Institute for Chemical Energy Conversion, 45470 Mülheim an der Ruhr, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Lubitz
authors.affiliation: the Karlsruhe Institute of Technology, Botanical Institute I, 76131 Karlsruhe, Germany.
authors.forename: Norbert
authors.initials: N
authors.lastname: Krauss
authors.affiliation: the Institut für Medizinische Physik und Biophysik (CC2), Group Protein X-ray Crystallography & Signal Transduction, Charité-Universitätsmedizin Berlin, 10117 Berlin, Germany, and.
authors.forename: Patrick
authors.initials: P
authors.lastname: Scheerer
authors.affiliation: the Justus-Liebig-Universität Giessen, Institut für Pflanzenphysiologie, 35390 Giessen, Germany.
authors.forename: Soshichiro
authors.initials: S
authors.lastname: Nagano
authors.affiliation: the Karlsruhe Institute of Technology, Botanical Institute I, 76131 Karlsruhe, Germany.
authors.forename: Tilman
authors.initials: T
authors.lastname: Lamparter
authors.affiliation: From the Albert-Ludwigs-Universität Freiburg, Institut für Physikalische Chemie, 79104 Freiburg, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Weber
mesh_terms: D060054:Agrobacterium / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D009154:Mutation; D010834:Phytochrome / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D013113:Spin Labels
chemical_list: D001426:Bacterial Proteins; D013113:Spin Labels; D010834:Phytochrome
keywords: PELDOR; SDSL; biliprotein; conformational change; dimerization; electron paramagnetic resonance (EPR); histidine kinase; photoreceptor; phytochrome; spectroscopy