Electrogenic reactions in Mn-depleted photosystem II core particles in the presence of synthetic binuclear Mn complexes

Liya A. Vitukhnovskaya, Sergey K. Zharmukhamedov, Mahdi M. Najafpour, Suleyman I. Allakhverdiev, Alexey Yu Semenov, Mahir D. Mamedov

Research output: Contribution to journalArticlepeer-review

Abstract

An electrometrical technique was used to investigate electron transfer between synthetic binuclear manganese (Mn) complexes, designated M − 2 and M − 3, and the redox-active neutral tyrosine radical (YZ ) in proteoliposomes containing Mn-depleted photosystem II (PS II) core particles in response to single laser flashes. In the absence of Mn-containing compounds, the observed flash-induced membrane potential (ΔΨ) decay was mainly due to charge recombination between the reduced primary quinone acceptor QA and the oxidized YZ . More significant slowing down of the ΔΨ decay in the presence of lower concentrations of M − 2 and M − 3 associated with electron donation from Mn in the Mn-binding site to YZ indicates that these synthetic compounds are more effective electron donors than MnCl2. The exponential fitting of the kinetics of additional electrogenic components of ΔΨ rise in the presence of Mn-containing compounds revealed the following relative amplitudes (A) and lifetimes (τ): for MnCl2 - A∼ 3.5, τ∼150 μs, for M − 2 - A∼5%, τ∼1.4 ms, and for M − 3 - A∼5.5%, τ∼150 μs. This suggests that the efficiency of the manganese complexes in electron donation depends on the chemical nature of ligands. The experiments with EDTA-treated samples indicated that the ligands for M − 2 and M − 3 are required for their tight binding with the PS II reaction center. The obtained results demonstrate the importance of understanding the molecular mechanism(s) of flash-induced electrogenic reduction of the tyrosine radical YZ by synthetic Mn complexes capable of splitting water into oxygen and reducing equivalents.

Original languageEnglish
Pages (from-to)222-227
Number of pages6
JournalBiochemical and Biophysical Research Communications
Volume503
Issue number1
DOIs
Publication statusPublished - Sep 3 2018

Keywords

  • Apo-WOC-PS II
  • Photosystem II
  • Photovoltage
  • Proteoliposomes
  • Reaction center
  • Synthetic binuclear Mn complexes

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology

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