title: Structural response of Photosystem 2 to iron deficiency: characterization of a new photosystem 2-IdiA complex from the cyanobacterium Thermosynechococcus elongatus BP-1.
abstract: Iron deficiency triggers various processes in cyanobacterial cells of which the synthesis of an additional antenna system (IsiA) around photosystem (PS) 1 is well documented [T.S. Bibby, J. Nield, J. Barber, Iron deficiency induces the formation of an antenna ring around trimeric photosystem I in cyanobacteria, Nature 412 (2001) 743-745, E.J. Boekema, A. Hifney, A.E. Yakushevska, M. Piotrowski, W. Keegstra, S. Berry, K.P. Michel, E.K. Pistorius, J. Kruip, A giant chlorophyll-protein complex induced by iron deficiency in cyanobacteria, Nature 412 (2001) 745-748]. Here we show that PS2 also undergoes prominent structural changes upon iron deficiency: Prerequisite is the isolation and purification of a PS2-IdiA complex which is exclusively synthesized under these conditions. Immunoblotting in combination with size exclusion chromatography shows that IdiA is only bound to dimeric PS2. Using single particle analysis of negatively stained specimens, IdiA can be localized in averaged electron micrographs on top of the CP43 subunit facing the cytoplasmic side in a model derived from the known 3D structure of PS2 [B. Loll, J. Kern, W. Saenger, A. Zouni, J. Biesiadka, Towards complete cofactor arrangement in the 3.0 A resolution structure of photosystem II, Nature 438 (2005) 1040-4]. The presence of IdiA as integral part of PS2 is the first example of a new PS2 protein being expressed under stress conditions, which is missing in highly purified PS2 complexes isolated from iron-sufficient cells.
authors.affiliation: Plant Biochemistry, Faculty of Biology, Ruhr-University Bochum, 44780 Bochum, Germany.
authors.forename: Julia E-M
authors.initials: JE
authors.lastname: Lax
authors.forename: Ana A
authors.initials: AA
authors.lastname: Arteni
authors.forename: Egbert J
authors.initials: EJ
authors.lastname: Boekema
authors.forename: Elfriede K
authors.initials: EK
authors.lastname: Pistorius
authors.forename: Klaus-Peter
authors.initials: KP
authors.lastname: Michel
authors.forename: Matthias
authors.initials: M
authors.lastname: Rögner
mesh_terms: D000458:Cyanobacteria / Q000737:chemistry*; D019281:Dimerization; D000090463:Iron Deficiencies; D033862:Iron-Binding Proteins / Q000378:metabolism* / Q000648:ultrastructure; D045332:Photosystem II Protein Complex / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism* / Q000648:ultrastructure; D011487:Protein Conformation
chemical_list: D033862:Iron-Binding Proteins; D045332:Photosystem II Protein Complex