Antenna complexes protect Photosystem I from Photoinhibition

Background Photosystems are composed of two moieties, a reaction center and a peripheral antenna system. In photosynthetic eukaryotes the latter system is composed of proteins belonging to Lhc family. An increasing set of evidences demonstrated how these polypeptides play a relevant physiological function in both light harvesting and photoprotection. Despite the sequence similarity between antenna proteins associated with the two Photosystems, present knowledge on their physiological role is mostly limited to complexes associated to Photosystem II. Results In this work we analyzed the physiological role of Photosystem I antenna system in Arabidopsis thaliana both in vivo and in vitro. Plants depleted in individual antenna polypeptides showed a reduced capacity for photoprotection and an increased production of reactive oxygen species upon high light exposure. In vitro experiments on isolated complexes confirmed that depletion of antenna proteins reduced the resistance of isolated Photosystem I particles to high light and that the antenna is effective in photoprotection only upon the interaction with the core complex. Conclusions We show that antenna proteins play a dual role in Arabidopsis thaliana Photosystem I photoprotection: first, a Photosystem I with an intact antenna system is more resistant to high light because of a reduced production of reactive oxygen species and, second, antenna chlorophyll-proteins are the first target of high light damages. When photoprotection mechanisms become insufficient, the antenna chlorophyll proteins act as fuses: LHCI chlorophylls are degraded while the reaction center photochemical activity is maintained. Differences with respect to photoprotection strategy in Photosystem II, where the reaction center is the first target of photoinhibition, are discussed

Jahrbuch des Archivs der deutschen Jugendbewegung. Vierter Band 1972

Entwicklungen des Laienspiels; Die Farben des Wandervogel; Aspekte des Wandels der Sozialstrukutr bündischer Gruppen vor und nach dem 2. Weltkriege; Bündische Gruppen in Österreich; Bund der Köngener, Bund Deutscher Jugendvereine; Nachruf

Bicarbonate binding to the water-oxidizing complex in the photosystem II. A Fourier transform infrared spectroscopy study1The authors would like to dedicate this paper to the memory of José V. Ibarra.1

AbstractThe light-induced Fourier transform infrared difference (FT-IR) spectrum originating from the donor side of O2-evolving photosystem (PS) II was obtained in non-depleted and CO2-depleted PSII membrane preparations. The observed spectrum free of contributions from the acceptor side signals was achieved by employing 2 mM/18 mM ferri-/ferrocyanide as a redox couple. This spectrum showed main positive bands at 1589 and 1365 cm−1 and negative bands at 1560, 1541, 1522 and 1507 cm−1. CO-depleted PSII preparations showed a quite different spectrum. The main positive and negative bands disappeared after depletion of bicarbonate. The addition of bicarbonate partially restored those bands again. Comparison between difference FT-IR spectra of untreated and bicarbonate-depleted PSII membranes indicated that the positive bands at 1589 and 1365 cm−1 can be assigned to COO− stretching modes from bicarbonate. The higher frequency corresponds to uas (COO−) and the lower frequency to us (COO−). 13C-Labeling FT-IR measurements confirmed these findings and also suggested that the negative band at 1560 cm−1 can be ascribed to uas (COO−). The data are discussed in the framework of the suggestion that bicarbonate can be a ligand to the Mn-containing water-oxidizing complex of PSII

Iron Coordination in Photosystem II: Interaction between Bicarbonate and the Q B Pocket Studied by Fourier Transform Infrared Spectroscopy

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Fourier transform infrared (FTIR) spectroscopy

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Transfert d'électrons et désexcitation de l'énergie chez les organismes photosynthétiques

AIX-MARSEILLE2-BU Sci.Luminy (130552106) / SudocSudocFranceF

Vibrational spectroscopy to study the properties of redox-active tyrosines in photosystem II and other proteins

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Bicarbonate binding to the non-heme iron of photosystem II, investigated by Fourier transform infrared difference spectroscopy and 13C-labeled bicarbonate.

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