The effect of mono- and divalent salts on the rise and decay kinetics of EPR signal II in Photosystem II preparations from spinach

Michael Boska, Neil V. Blough, Kenneth Sauer

Research output: Contribution to journalArticle

12 Scopus citations

Abstract

The rise and decay kinetics of EPR signal II have been used to probe the organization of the donor side of Photosystem II (PS II) before and after extraction of PS II preparations with high concentrations of salt. 800 mM NaCl or 500-800 mM NaBr substantially depletes the preparations of the 16 and 24 kDa proteins and decreases the steady-state rate of O2-evolution by 70-80% from control rates. These treatments do not largely alter the decay kinetics of Signal II; the rise kinetics remain in the instrument limited time range (2 μs or less) during the first 8-12 flashes. Treating PS II preparations with 800 mM CaCl2 removes the 16, 24 and 33 kDa proteins with at least 95% inhibition of the steady-state rates of O2 evolution. The additional removal of the 33 kDa polypeptide decreases the rates of oxidation and rereduction of Z, the species responsible for Signal II. Preparations treated with either mono- or divalent salts show a steady-state light-induced increase in Signal II similar to that seen in Tris-washed samples. Such a steady-state increase indicates that the rate of electron transport from water to Z is greatly decreased or blocked. The data are interpreted within a model in which there is an intermediate electron carrier between the O2 evolving complex and Z.

Original languageEnglish (US)
Pages (from-to)132-139
Number of pages8
JournalBBA - Bioenergetics
Volume808
Issue number1
DOIs
StatePublished - Jun 26 1985
Externally publishedYes

Keywords

  • (Spinach)
  • ESR
  • Electron transport
  • Oxygen evolution
  • Photosystem II
  • Salt effect

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology

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