Two sites of photoinhibition of the electron transfer in oxygen evolving and Tris-treated PS II membrane fragments from spinach

Eckert, Hann-Jörg; Geiken, B.; Bernarding, Johannes; Napiwotzki, A.; Eichler, Hans Joachim; Ренгер, Г.

doi:10.1007/bf00033249

Cited by 117 publications

(102 citation statements)

References 54 publications

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“…Photoinhibition on the acceptor side has been proposed to be primarily induced by the overreduction of the primary acceptor, Q A , to Q A H 2 and the subsequent release of Q A H 2 from PSII (Vass et al, 1992). Photoinhibition on the donor side has been shown to be due to photoinactivation of the electron transfer from Y Z to P680 when the oxygen-evolving complex is inactivated (Eckert et al, 1991).…”

Section: Introductionmentioning

confidence: 99%

Formation of DEG5 and DEG8 Complexes and Their Involvement in the Degradation of Photodamaged Photosystem II Reaction Center D1 Protein in Arabidopsis

et al. 2007

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The widely distributed DEGP proteases play important roles in the degradation of damaged and misfolded proteins. Arabidopsis thaliana contains 16 DEGP-like proteases, four of which are located in the chloroplast. Here, we show that DEG5 and DEG8 form a hexamer in the thylakoid lumen and that recombinant DEG8 is proteolytically active toward both a model substrate (b-casein) and photodamaged D1 protein of photosystem II (PSII), producing 16-kD N-terminal and 18-kD C-terminal fragments. Inactivation of DEG5 and DEG8 resulted in increased sensitivity to photoinhibition. Turnover of newly synthesized D1 protein in the deg5 deg8 double mutant was impaired, and the degradation of D1 in the presence of the chloroplast protein synthesis inhibitor lincomycin under high-light treatment was slowed in the mutants. Thus, DEG5 and DEG8 are important for efficient turnover of the D1 protein and for protection against photoinhibition in vivo. The deg5 deg8 double mutant showed increased photosensitivity and reduced rates of D1 degradation compared with single mutants of deg5 and deg8. A 16-kD N-terminal degradation fragment of the D1 protein was detected in wild-type plants but not in the deg5 deg8 mutant following in vivo photoinhibition. Therefore, our results suggest that DEG5 and DEG8 have a synergistic function in the primary cleavage of the CD loop of the PSII reaction center protein D1.

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Section: Introductionmentioning

confidence: 99%

Formation of DEG5 and DEG8 Complexes and Their Involvement in the Degradation of Photodamaged Photosystem II Reaction Center D1 Protein in Arabidopsis

et al. 2007

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“…9 based on light absorbed by PSII pigments) is the same order of magnitude as that of the photoinhibition of oxygen-evolving PSII membrane fragments (29) or as can be estimated by recalculating from photoinhibition of isolated thylakoids illuminated in the absence of added electron acceptors (30,31). This similarity suggests that the aerobic acceptor-side photoinhibition in vitro may occur with the same mechanism as photoinhibition in vivo.…”

Section: Resultsmentioning

confidence: 99%

The rate constant of photoinhibition, measured in lincomycin-treated leaves, is directly proportional to light intensity.

Tyystjärvi

Aro

1996

Proc. Natl. Acad. Sci. U.S.A.

434

268

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Pumpkin leaves grown under high light (500-700 ,umol of photons m-2 s'1) were illuminated under photon flux densities ranging from 6.5 to 1500 ,umol-m-2-s'1 in the presence of lincomycin, an inhibitor of chloroplast protein synthesis. The illumination at all light intensities caused photoinhibition, measured as a decrease in the ratio of variable to maximum fluorescence. Loss of photosystem II (PSII) electron transfer activity correlated with the decrease in the fluorescence ratio. The rate constant of photoinhibition, determined from first-order fits, was directly proportional to photon flux density at all light intensities studied. photon flux density (4). However, these experiments were done under high, photoinhibitory light, and it therefore remained unclear if photoinhibition is somehow related to the photon flux exceeding the flux that can be safely dissipated through photosynthesis (5-7). On the contrary, the first-order nature of photoinhibition suggests that each photon absorbed by PSII causes photoinhibition with the same probability. In the present paper, we describe results that prove the latter.The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact. 2213Reciprocity between the amount of light and the duration of illumination was demonstrated for photoinhibition of isolated chloroplasts by Jones and Kok (8). Very recently, Park et al. (9) published data demonstrating that the law of reciprocity holds for photoinhibition of intact leaves too. The present study confirms most of their results, but we conclude that photoinhibition is a one-photon phenomenon instead of a photon counter-type poisoning process (9).The degradation and synthesis of the Dl protein are rapid under both high and low light if compared to other thylakoid proteins (10), and several hypotheses have been put forward to explain the reasons for the fast turnover. The high-lightdependent and normal turnover of the DI protein have often been treated separately because photoinhibition has been considered to be limited to light levels above the saturation of photosynthesis and because it has been assumed that photoinhibitory damage does not occur at low light. It was even suggested that the Dl protein turns over for reasons not at all related to light-induced damage to PSII (11). The rapid resynthesis of the Dl protein usually makes it impossible to detect the light-dependent loss of the Dl protein if the synthesis is not blocked during the experiment. Furthermore, since the Dl protein is degraded after but not simultaneously with photoinhibition of the reaction center, the dependence of the rate of degradation on light is far from linear (3). It must also be noted that because neither photoinhibition nor degradation of the Dl protein occurs with zero-order kinetics, fixed-time assays have no relevance with respect to the kinetics. The complexity of the kinetics has promoted the s...

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“…Excitation by single turnover flashes given at a low repetition rate can mimic low levels of continuous illumination if the repetition rate of the light flashes is low enough to prevent rapid double reduction of Q B , by consecutive flashes and its protonation to plastoquinol (15). To test the hypothesis that under such conditions, back electron flow from Q B…”

Section: Resultsmentioning

confidence: 99%

Mechanism of photosystem II photoinactivation and D1 protein degradation at low light: The role of back electron flow

Keren

Berg

Kan

et al. 1997

Proc. Natl. Acad. Sci. U.S.A.

280

196

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Light intensities that limit electron f low induce rapid degradation of the photosystem II (PSII) reaction center D1 protein. The mechanism of this phenomenon is not known. We propose that at low excitation rates back electron f low and charge recombination between the Q B• Following the discovery of the light dependent turnover of reaction center II (RCII) D1 protein (1), the process of excess light-induced photoinactivation and the related degradation of photosystem II (PSII) proteins (photoinhibition) were studied intensively. Significant progress toward understanding the mechanism(s) involved was achieved (reviewed in refs. [2][3][4]

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Two sites of photoinhibition of the electron transfer in oxygen evolving and Tris-treated PS II membrane fragments from spinach

Cited by 117 publications

References 54 publications

Formation of DEG5 and DEG8 Complexes and Their Involvement in the Degradation of Photodamaged Photosystem II Reaction Center D1 Protein in Arabidopsis

Formation of DEG5 and DEG8 Complexes and Their Involvement in the Degradation of Photodamaged Photosystem II Reaction Center D1 Protein in Arabidopsis

The rate constant of photoinhibition, measured in lincomycin-treated leaves, is directly proportional to light intensity.

Mechanism of photosystem II photoinactivation and D1 protein degradation at low light: The role of back electron flow

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