Peculiarities of Mn(II) Cation Oxidation in the Photosystem II without an Oxygen-Evolving Complex: Evolutionary Aspect

One of the main reactions in the process of light energy transformation in oxygenic organisms is the extraction of electrons from water, which are necessary for the light stage of photosynthesis. The light-dependent oxidation of water is carried out by an oxygen-evolving complex (OEC), the catalytic...

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Bibliographic Details
Published in:Moscow University biological sciences bulletin 2022-06, Vol.77 (2), p.92-97
Main Authors: Lovyagina, E. R., Davletshina, L. N., Semin, B. K.
Format: Article
Language:English
Subjects:
Biochemistry
Biomedical and Life Sciences
Cations
Cell Biology
Dichlorophenolindophenol
Environmental factors
Evolution
Hydrogen peroxide
Life Sciences
Manganese
Oxidation
Oxygen
Photosynthesis
Photosystem II
Plant Sciences
Research Article
Thylakoid membranes
Zoology
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Summary:One of the main reactions in the process of light energy transformation in oxygenic organisms is the extraction of electrons from water, which are necessary for the light stage of photosynthesis. The light-dependent oxidation of water is carried out by an oxygen-evolving complex (OEC), the catalytic center of which is the cluster Mn 4 CaO 5 . OEC is located in photosystem II (PSII) on the lumen side of the thylakoid membrane. The evolutionary origin of the PSII is unclear, as is the origin of the manganese cluster in the OEC. Recently, Johnson et al. (2013) suggested that, in the primary PSII in the Archean period, the cluster Mn 4 CaO 5 was absent, and PSII oxidized not water but Mn (II) cations, i.e., manganese cations were the source of electrons. In the presented work, the authors investigated the possibility of the influence of some environmental factors (citrate and hydrogen peroxide) on the oxidation rate of Mn(II) cations by a PSII that does not contain OEC. It was found that citrate inhibit the oxidation of Mn(II) cations binding them but does not extract Mn cations from OEC. Hydrogen peroxide, on the contrary, significantly increases the oxidation rate of manganese (from 28 ± 2 to 145 ± 7 µmol 2,6-dichlorophenolindophenol mg Chl –1 h –1 in the presence of H 2 O 2 ). Such effects should be taken into account when investigating the oxidation of manganese cations by the photosystem as a possible source of electrons in the early stages of evolution.
ISSN:0096-3925
1934-791X
DOI:10.3103/S0096392522020055