title: Kinetics of the LOV domain of ZEITLUPE determine its circadian function inArabidopsis.
abstract: A LOV (Light, Oxygen, or Voltage) domain containing blue-light photoreceptor ZEITLUPE (ZTL) directs circadian timing by degrading clock proteins in plants. Functions hinge upon allosteric differences coupled to the ZTL photocycle; however, structural and kinetic information was unavailable. Herein, we tune the ZTL photocycle over two orders of magnitude. These variants reveal that ZTL complexes with targets independent of light, but dictates enhanced protein degradation in the dark. In vivo experiments definitively show photocycle kinetics dictate the rate of clock component degradation, thereby impacting circadian period. Structural studies demonstrate that photocycle dependent activation of ZTL depends on an unusual dark-state conformation of ZTL. Crystal structures of ZTL LOV domain confirm delineation of structural and kinetic mechanisms and identify an evolutionarily selected allosteric hinge differentiating modes of PAS/LOV signal transduction. The combined biochemical, genetic and structural studies provide new mechanisms indicating how PAS/LOV proteins integrate environmental variables in complex networks.
authors.affiliation: Department of Chemistry, Southern Methodist University, Dallas, United States.|Center for Drug Discovery, Design and Delivery, Southern Methodist University, Dallas, United States.
authors.forename: Ashutosh
authors.initials: A
authors.lastname: Pudasaini
authors.affiliation: Department of Biology, University of Washington, Seattle, United States.
authors.forename: Jae Sung
authors.initials: JS
authors.lastname: Shim
authors.affiliation: Department of Biology, University of Washington, Seattle, United States.|Department of Life Sciences, Ajou University, Suwon, Korea.
authors.forename: Young Hun
authors.initials: YH
authors.lastname: Song
authors.affiliation: Department of Molecular Genetics, Ohio State University, Columbus, United States.
authors.forename: Hua
authors.initials: H
authors.lastname: Shi
authors.affiliation: RIKEN Center for Sustainable Resource Science, Yokohama, Japan.
authors.forename: Takatoshi
authors.initials: T
authors.lastname: Kiba
authors.affiliation: Department of Molecular Genetics, Ohio State University, Columbus, United States.
authors.forename: David E
authors.initials: DE
authors.lastname: Somers
authors.affiliation: Department of Biology, University of Washington, Seattle, United States.
authors.forename: Takato
authors.initials: T
authors.lastname: Imaizumi
authors.affiliation: Department of Chemistry, Southern Methodist University, Dallas, United States.|Center for Drug Discovery, Design and Delivery, Southern Methodist University, Dallas, United States.
authors.forename: Brian D
authors.identifier: 0000-0001-6749-0743
authors.initials: BD
authors.lastname: Zoltowski
mesh_terms: D017360:Arabidopsis / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism*; D057906:Circadian Clocks; D018360:Crystallography, X-Ray; D003624:Darkness; D007700:Kinetics; D008027:Light; D008958:Models, Molecular; D011487:Protein Conformation; D059748:Proteolysis
chemical_list: D029681:Arabidopsis Proteins; C410503:ZTL protein, Arabidopsis
keywords: A. thaliana; LOV domain; allostery; biophysics; circadian clock; plant biology; structural biology