The Thermal Stability of Electron Transfer in Membrane Preparations of Photosystem II with a Ca2+-Depleted Oxygen-Evolving Complex

The temperature stability of electron transfer to the artificial electron acceptor 2,6-dichlorophenolindophenol in preparations of native photosystem II and photosystem II without the calcium cation in an oxygen-evolving complex was studied. The thermal stability of the processes of oxygen evolution...

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Bibliographic Details
Published in:Biophysics (Oxford) 2021, Vol.66 (1), p.65-69
Main Authors: Lovyagina, E. R., Semin, B. K.
Format: Article
Language:English
Subjects:
Biological and Medical Physics
Biophysics
Calcium
Cell Biophysics
Chemical reduction
Cytochrome
Cytochrome c
Dichlorophenolindophenol
Electron transfer
Manganese
Oxygen
Photosystem II
Physics
Physics and Astronomy
Thermal stability
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Summary:The temperature stability of electron transfer to the artificial electron acceptor 2,6-dichlorophenolindophenol in preparations of native photosystem II and photosystem II without the calcium cation in an oxygen-evolving complex was studied. The thermal stability of the processes of oxygen evolution and electron transfer from the oxygen-evolving complex to 2,6-dichlorophenolindophenol in photosystem II were significantly different: the reduction of 2,6-dichlorophenolindophenol was more resistant to temperature than oxygen evolution. The reaction of 2,6-dichlorophenolindophenol reduction in the Ca 2+ -depleted preparations of photosystem II was less resistant to heating than in the preparations of native photosystem II. The thermal inactivation of the photosystem II in the Ca 2+ -depleted membrane preparations was inhibited by cytochrome c at a concentration of 50 cytochrome c molecules per a photosystem II reaction center. The activity of this preparation (the rate of the 2,6-dichlorophenolindophenol reduction) increased by 19%, approaching the activity of the native photosystem II. The protective effect of cytochrome c appears to be determined by its protein nature, rather than its redox activity, since an equal protective effect was observed upon the addition of albumin at a similar concentration. Almost complete inactivation of the 2,6-dichlorophenolindophenol reduction reaction in the native and Ca 2+ -depleted preparations of photosystem II was observed at the same temperature (50°C). According to the EPR data, photosystem II in the Ca 2+ -depleted preparation after incubation at this temperature lacked a manganese cluster, while a peripheral protein of 33 kDa was present.
ISSN:0006-3509
1555-6654
DOI:10.1134/S0006350921010097