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Updated: Jun 13, 2026

Developing Photosensitizer-Cobaloxime Hybrids for Solar-Driven H2 Production in Aqueous Aerobic Conditions
Published on: October 5, 2019
Interaction of bicarbonate with the manganese-stabilizing protein of photosystem II
Olga V Pobeguts1, Tatiana N Smolova, Dmitry S Timoshevsky
1Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Moscow Region 142290, Russia. nikitishena@mail.ru
Abstract:
The effect of reversible removal of HCO(3)(-) on structural re-arrangements in the Mn-stabilizing protein (MSP) of photosystem II, isolated from pea leaves, was studied using measurements of characteristic alterations in fluorescence of hydrophobic probe 8-anilino-1-naphthalene-sulfonic acid (ANS). It was shown that the treatments capable of removal of HCO(3)(-) (or CO(2)) from possible binding sites in MSP (pH lowering from 6.5 to 3.5, addition of a structurally similar anion HCO(3)(-) in concentration 1-20mM or air evacuation at pH 3.5) result in a significant (up to 370%) increase of ANS fluorescence (indicative of structural changes in MSP), whereas HCO(3)(-) lowers the ANS fluorescence to the initial level observed in untreated protein at pH 6.5. Since the effects are revealed at (sub)micromolar concentrations of HCO(3)(-), the specific high-affinity binding of HCO(3)(-) (or CO(2)) to MSP (required for its native structure preservation) is proposed. Possible bicarbonate binding sites and its physiological role within the water-oxidizing complex of photosystem II are discussed.
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