In photoinhibited photosystem II particles pheophytin photoreduction remains unimpaired

Allakhverdiev, S.I.; S̆etlíková, Eva; Klimov, Vyacheslav V.; Šetlík, Ivan

doi:10.1016/0014-5793(87)80576-8

Cited by 78 publications

(40 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…5). This finding is qualitatively supported by earlier experiments demonstrating that the rate of photoinhibition is faster under strongly reducing conditions (14)(15)(16)(17).…”

Section: Discussionsupporting

confidence: 80%

Redox state of a one-electron component controls the rate of photoinhibition of photosystem II.

Nedbal

Samson

Whitmarsh

1992

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

View full text Add to dashboard Cite

Photosystem H reaction centers in plants, algae, and cyanobacteria are susceptible to damage by excess light that irreversibly impairs activity and eventually results in the proteolytic degradation of at least one of the core proteins. Oxygenic photosynthetic organisms are vulnerable to damage by a number of environmental factors, including visible light, UV-B radiation, heat, cold, drought, and atmospheric pollutants (1). In some cases, the site of damage is the photosystem II (PSII) reaction center, a membrane-bound, multisubunit complex that catalyzes the oxidation of water and the reduction of plastoquinone (2). The PSII reaction center provides approximately half the energy used for biomass production in plants and is responsible for the release of molecular oxygen into the atmosphere. The reaction center core is composed of the a and f8 subunits of cytochrome b-559 (Cyt b559) and the two proteins, D1 and D2, that bind the redox components known to be required for electron transfer from the water-oxidizing manganese cluster to plastoquinone. These include the primary donor (P680), the secondary donor (Yz), the primary acceptor pheophytin (Pheo), and the primary and secondary plastoquinone acceptors (QA and QB).Exposure of PSII to supersaturating levels of visible light causes the loss of water oxidation (3) and eventually leads to removal and degradation of the D1 polypeptide (4). There is disagreement concerning the early events that lead to photoinhibition of the reaction center (reviewed in ref. 5). Using thylakoid membranes as model systems, some experiments show that the initial site of damage is on the oxidizing side of PSII, whereas other experiments, often done under different conditions, show that the primary site of damage is on the reducing side of PSII. These results form the basis for two models of photoinhibition: those that focus on damage done by the highly oxidizing cation radicals and those that focus on damage done by the highly reducing anion radicals.This study was initiated to investigate the molecular mechanism of PSII photoinhibition and protective reactions. Potentiometric titrations reveal that a one-electron redox component plays a critical role in the process. The rate of PSII damage is dramatically increased when the component is reduced. We suggest that the redox component is the lowpotential form of Cyt b559 (Cyt b559LP), which protects the reaction center from photoinhibition by providing an alternative electron pathway that can oxidize the damaging radical state P680/Pheo-/QA-MATERIALS AND METHODS Membrane Isolation. Spinach leaves (Spinacia oleracea) were either harvested from plants grown hydroponically (6) or bought from a local market. Thylakoid membranes were isolated from leaves as described (7) and stored on ice at a chlorophyll concentration of 1-2 mM in medium containing 5 mM Hepes-NaOH (pH 7.5), 200 mM sorbitol, 2 mM MgCl2, and fatty acid-free bovine serum albumin (0.5 mg/ml). The membranes were used for experiments within 7 h ofisolation. Chlorophyll conce...

show abstract

“…5). This finding is qualitatively supported by earlier experiments demonstrating that the rate of photoinhibition is faster under strongly reducing conditions (14)(15)(16)(17).…”

Section: Discussionsupporting

confidence: 80%

Redox state of a one-electron component controls the rate of photoinhibition of photosystem II.

Nedbal

Samson

Whitmarsh

1992

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

View full text Add to dashboard Cite

show abstract

“…(-o-) or absence (-c-) of oxygen or to low light (10/E) in the [ 10,25,26]. Moreover, under anaerobic conditions no degradation of the Dl-protein could be seen as judged by immunoblotting (Table I).…”

Section: Resultsmentioning

confidence: 99%

Restoration of light induced photosystem II inhibition without de novo protein synthesis

et al. 1990

View full text Add to dashboard Cite

show abstract

“…The rate and extent of the F0 increase ( Fig. 1, curves []), which accompanies the fast photoinactivation (see also Allakhverdiev et al 1987, Setlik et al 1989, are at maximum under R-conditions and are high under A-conditions. The photoreduction of DCPIP by the particles is suppressed approximately in parallel to the F0 rise, i.e.…”

Section: Resultsmentioning

confidence: 99%

“…Spectrophotometer was in dual wavelength mode with reference wavelength set always to the isosbestic point at 678.5 nm. Difference absorption spectrum was identical to that published earlier (Allakhverdiev et al 1987). To be sure that the signal was not influenced by fluorescence or by chlorophyll bleaching, we measured AA650 and AA676 in parallel tO AA685.…”

Section: Spectroscopy and Photosynthetic Activity Measurementsmentioning

confidence: 90%

Three types of Photosystem II photoinactivation

et al. 1990

Self Cite

View full text Add to dashboard Cite

Oxygen evolving Photosystem II particles were exposed for up to 10 h to 100 W m(-2) white light at 20°C under aerobic, low oxygen, strictly anaerobic and strongly reducing conditions. The fast and slow photoinactivation processes described earlier (Šetlík et al. 1989) were observed during the first 120 min. The third and by far the slowest process impaired the primary charge separation P680(+)-Pheo(-). Its half-time was about 2.5 h under aerobic and strongly reducing conditions and about 4 h under anaerobic and low oxygen conditions. In these time intervals there were no changes in the chlorophyll-protein and polypeptide composition of the particles irradiated under anaerobic, low oxygen or strongly reducing conditions while a dramatic degradation of chlorophyll-proteins and polypeptides occurred under aerobic conditions.

show abstract

In photoinhibited photosystem II particles pheophytin photoreduction remains unimpaired

Cited by 78 publications

References 23 publications

Redox state of a one-electron component controls the rate of photoinhibition of photosystem II.

Redox state of a one-electron component controls the rate of photoinhibition of photosystem II.

Restoration of light induced photosystem II inhibition without de novo protein synthesis

Three types of Photosystem II photoinactivation

Contact Info

Product

Resources

About