title: Allosteric communication between DNA-binding and light-responsive domains of diatom class I aureochromes.
abstract: The modular architecture of aureochrome blue light receptors, found in several algal groups including diatoms, is unique by having the LOV-type photoreceptor domain fused to the C-terminus of its putative effector, an N-terminal DNA-binding bZIP module. The structural and functional understanding of aureochromes' light-dependent signaling mechanism is limited, despite their promise as an optogenetic tool. We show that class I aureochromes 1a and 1c from the diatom Phaeodactylum tricornutum are regulated in a light-independent circadian rhythm. These aureochromes are capable to form functional homo- and heterodimers, which recognize the ACGT core sequence within the canonical 'aureo box', TGACGT, in a light-independent manner. The bZIP domain holds a more folded and less flexible but extended conformation in the duplex DNA-bound state. FT-IR spectroscopy in the absence and the presence of DNA shows light-dependent helix unfolding in the LOV domain, which leads to conformational changes in the bZIP region. The solution structure of DNA bound to aureochrome points to a tilted orientation that was further validated by molecular dynamics simulations. We propose that aureochrome signaling relies on an allosteric pathway from LOV to bZIP that results in conformational changes near the bZIP-DNA interface without major effects on the binding affinity.
authors.affiliation: Structural Biochemistry - Department of Chemistry, Philipps University Marburg, Hans-Meerwein Straße 4, 35032 Marburg, Germany.
authors.forename: Ankan
authors.initials: A
authors.lastname: Banerjee
authors.affiliation: Physical and Biophysical Chemistry - Department of Chemistry, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany.
authors.forename: Elena
authors.initials: E
authors.lastname: Herman
authors.affiliation: Plant Ecophysiology - Department of Biology, University of Konstanz, 78457 Konstanz, Germany.
authors.forename: Manuel
authors.initials: M
authors.lastname: Serif
authors.affiliation: Institute of Biological Chemistry, Academia Sinica, 128 Academia Road, Sec. 2 Nankang, Taipei 11529, Taiwan.
authors.forename: Manuel
authors.initials: M
authors.lastname: Maestre-Reyna
authors.affiliation: Structural Biochemistry - Department of Chemistry, Philipps University Marburg, Hans-Meerwein Straße 4, 35032 Marburg, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Hepp
authors.affiliation: Faculty of Biology, Department of Plant Physiology and Photobiology, Philipps-University Marburg, 35043 Marburg, Germany.
authors.forename: Richard
authors.initials: R
authors.lastname: Pokorny
authors.affiliation: Plant Ecophysiology - Department of Biology, University of Konstanz, 78457 Konstanz, Germany.
authors.forename: Peter G
authors.identifier: 0000-0003-4734-8955
authors.initials: PG
authors.lastname: Kroth
authors.affiliation: Structural Biochemistry - Department of Chemistry, Philipps University Marburg, Hans-Meerwein Straße 4, 35032 Marburg, Germany essen@chemie.uni-marburg.de.
authors.forename: Lars-Oliver
authors.initials: LO
authors.lastname: Essen
authors.affiliation: Physical and Biophysical Chemistry - Department of Chemistry, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany.
authors.forename: Tilman
authors.initials: T
authors.lastname: Kottke
mesh_terms: D000494:Allosteric Regulation; D001665:Binding Sites; D002940:Circadian Rhythm / Q000235:genetics; D004247:DNA / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017377:Diatoms / Q000235:genetics* / Q000378:metabolism / Q000528:radiation effects; D015870:Gene Expression; D007700:Kinetics; D008027:Light; D055537:Light Signal Transduction; D056004:Molecular Dynamics Simulation; D009690:Nucleic Acid Conformation; D059372:Nucleotide Motifs; D055519:Photoreceptors, Plant / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D000072417:Protein Domains; D055503:Protein Multimerization; D013816:Thermodynamics
chemical_list: D055519:Photoreceptors, Plant; D004247:DNA