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

• Published in: Biophysics (Oxford) Vol. 66; no. 1; pp. 65 - 69
• Main Authors: Lovyagina, E. R., Semin, B. K.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 2021; Springer Nature B.V
• 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; photosystem II; calcium; temperature stability; oxygen-evolving complex
• ISSN: 0006-3509; 1555-6654
• DOI: 10.1134/S0006350921010097

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.