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Updated: Aug 3, 2025

Purification of Active Photosystem I-Light Harvesting Complex I from Plant Tissues
Published on: February 3, 2023
High-efficiency oxygen evolution by photosystem II oxygen-evolving complex containing 3Mn per reaction center
Boris К Semin1, Lira N Davletshina2
1Department of Biophysics, Faculty of Biology, Moscow State University, Moscow, 119234, Russia. seminbk@mail.ru.
Abstract:
Ca-depleted photosystem II membranes obtained by treatment with acidic buffer do not contain Ca2+ in the Mn4CaO5 cluster but contain all extrinsic proteins protecting this cluster (PSII(-Ca/low pH)). However, unlike native photosystem II, Mn cluster in PSII(-Ca/low pH) samples is available for small-sized reductants. Using this property, we investigated the substitution possibility of Mn cation(s) with Fe cation(s) to obtain a chimeric cluster in PSII(-Ca/low pH) samples containing extrinsic proteins. We found that Fe(II) cation replaces Mn cation at pH 6.5, however, PSII(-Ca/low pH) membranes with the 3Mn1Fe chimeric cluster in the oxygen-evolving complex evolve O2 with high intensity in the presence of exogenous Ca2+. The O2 evolution rate is about 80% of the same rate in PSII(-Ca/low pH) membranes.
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