title: The PsbY protein of Arabidopsis Photosystem II is important for the redox control of cytochrome b559.
abstract: Photosystem II is a protein complex embedded in the thylakoid membrane of photosynthetic organisms and performs the light driven water oxidation into electrons and molecular oxygen that initiate the photosynthetic process. This important complex is composed of more than two dozen of intrinsic and peripheral subunits, of those half are low molecular mass proteins. PsbY is one of those low molecular mass proteins; this 4.7-4.9kDa intrinsic protein seems not to bind any cofactors. Based on structural data from cyanobacterial and red algal Photosystem II PsbY is located closely or in direct contact with cytochrome b559. Cytb559 consists of two protein subunits (PsbE and PsbF) ligating a heme-group in-between them. While the exact function of this component in Photosystem II has not yet been clarified, a crucial role for assembly and photo-protection in prokaryotic complexes has been suggested. One unique feature of Cytb559 is its redox-heterogeneity, forming high, medium and low potential, however, neither origin nor mechanism are known. To reveal the function of PsbY within Photosystem II of Arabidopsis we have analysed PsbY knock-out plants and compared them to wild type and to complemented mutant lines. We show that in the absence of PsbY protein Cytb559 is only present in its oxidized, low potential form and plants depleted of PsbY were found to be more susceptible to photoinhibition.
authors.affiliation: Department of Chemistry, Umeå University, SE-901 87 Umeå, Sweden.
authors.forename: Lotta
authors.initials: L
authors.lastname: von Sydow
authors.affiliation: Department Biologie I, Ludwig-Maximilians-University Munich, 82152 Planegg-Martinsried, Germany.
authors.forename: Serena
authors.initials: S
authors.lastname: Schwenkert
authors.affiliation: Department Biologie I, Ludwig-Maximilians-University Munich, 82152 Planegg-Martinsried, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Meurer
authors.affiliation: Department of Chemistry, Umeå University, SE-901 87 Umeå, Sweden.
authors.forename: Christiane
authors.initials: C
authors.lastname: Funk
authors.affiliation: Molecular Biomimetics, Department of Chemistry - Ångström Laboratory, Box 523, Uppsala University, SE-751 20 Uppsala, Sweden.
authors.forename: Fikret
authors.initials: F
authors.lastname: Mamedov
authors.affiliation: Department of Chemistry, Umeå University, SE-901 87 Umeå, Sweden. Electronic address: Wolfgang.Schroder@umu.se.
authors.forename: Wolfgang P
authors.initials: WP
authors.lastname: Schröder
mesh_terms: D029681:Arabidopsis Proteins / Q000502:physiology*; D003573:Cytochrome b Group / Q000502:physiology*; D004578:Electron Spin Resonance Spectroscopy; D010084:Oxidation-Reduction; D045332:Photosystem II Protein Complex / Q000502:physiology*; D013819:Thermoluminescent Dosimetry; D014512:Ureohydrolases / Q000502:physiology*
chemical_list: D029681:Arabidopsis Proteins; D003573:Cytochrome b Group; D045332:Photosystem II Protein Complex; C019313:cytochrome b559; C492035:PSBY protein, Arabidopsis; D014512:Ureohydrolases
keywords: Cytochrome b(559); Photosystem II; PsbY protein; Thylakoid membrane