Toxic Cu (II) effect on cytochrome b(559) under aerobic photoinhibitory conditions was examined in two different photosystem II (PSII) membrane preparations active in oxygen evolution. The preparations differ in the content of cytochrome b(559) redox potential forms. Difference absorption spectra showed that the presence of Cu (II) induced the oxidation of the high-potential form of cytochrome b(559) in the dark. Addition of hydroquinone reduced the total oxidized high-potential form of cytochrome b(559) present in Cu (II)-treated PSII membranes indicating that no conversion to the low-potential form took place. Spectroscopic determinations of cytochrome b(559) during photoinhibitory treatment showed slower kinetics of Cu (II) effect on cytochrome b(559) in comparison with the rapid loss of oxygen evolution activity in the same conditions. This result indicates that cytochrome b(559) is affected after PSII centres are photoinhibited. The high-potential form was more sensitive to toxic Cu (II) action than the low-potential form under illumination at pH 6.0. The content of the high-potential form of cytochrome b(559) was completely lost; however, the low-potential content was unaffected in these conditions. This loss did not involve cytochrome protein degradation. The results are discussed in terms of different binding properties of the heme iron to the protonated or unprotonated histidine ligand in the high-potential and low-potential forms of cytochrome b(559), respectively.
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http://dx.doi.org/10.1111/j.1399-3054.2004.0286.x | DOI Listing |
Plant Cell
September 2024
Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam-Golm, Germany.
The cytochrome b559 heterodimer is a conserved component of photosystem II whose physiological role in photosynthetic electron transfer is enigmatic. A particularly puzzling aspect of cytochrome b559 has been its presence in etiolated seedlings, where photosystem II is absent. Whether or not the cytochrome has a specific function in etioplasts is unknown.
View Article and Find Full Text PDFPlant Cell
October 2024
Development Center of Plant Germplasm Resources, College of Life Sciences, Shanghai Normal University, Shanghai 200234, China.
As an essential intrinsic component of photosystem II (PSII) in all oxygenic photosynthetic organisms, heme-bridged heterodimer cytochrome b559 (Cyt b559) plays critical roles in the protection and assembly of PSII. However, the underlying mechanisms of Cyt b559 assembly are largely unclear. Here, we characterized the Arabidopsis (Arabidopsis thaliana) rph1 (resistance to Phytophthora1) mutant, which was previously shown to be susceptible to the oomycete pathogen Phytophthora brassicae.
View Article and Find Full Text PDFNat Commun
June 2024
Key Laboratory of Biomacromolecules (CAS), National Laboratory of Biomacromolecules, CAS Centre for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China.
Photosystem II (PSII) catalyzes water oxidation and plastoquinone reduction by utilizing light energy. It is highly susceptible to photodamage under high-light conditions and the damaged PSII needs to be restored through a process known as the PSII repair cycle. The detailed molecular mechanism underlying the PSII repair process remains mostly elusive.
View Article and Find Full Text PDFEnviron Pollut
May 2024
School of Geosciences, University of South Florida, Tampa, FL, 33620, USA; Department of Ecology and Environmental Studies, Florida Gulf Coast University, Fort Myers, Florida, USA. Electronic address:
Hydrogen peroxide is a reactive oxygen species (ROS) naturally occurring at low levels in aquatic environments and production varies widely across different ecosystems. Oxygenic photosynthesis generates hydrogen peroxide as a byproduct, of which some portion can be released to ambient water. However, few studies have examined hydrogen peroxide dynamics in relation to cyanobacterial harmful algal blooms (cHABs).
View Article and Find Full Text PDFFront Plant Sci
January 2024
The George S. Wise Faculty of Life Sciences, Department of Biochemistry and Molecular Biology, Tel Aviv University, Tel Aviv, Israel.
Photosystem II (PSII) is a dimer consisting of at least 13 nuclear-encoded and four chloroplast-encoded protein subunits that collectively function as a sunlight-driven oxidoreductase. In this study, we present the inaugural structure of a green alga PSII assembly intermediate (pre-PSII-int). This intermediate was isolated from chloroplast membranes of the temperature-sensitive mutant TSP4, cultivated for 14 hours at a non-permissive temperature.
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