EPR signal II in cyanobacterial Photosystem II reaction-center complexes with and without the 40 kDa chlorophyll-binding subunit

Michael Boska, Akihiko Yamagishi, Kenneth Sauer

Research output: Contribution to journalArticle

8 Scopus citations

Abstract

The steady-state amplitude and flash-induced kinetics of EPR signal II in two Photosystem II (PS II) reaction center protein complexes from Synechococcus were measured to probe the organization of species involved in the PS II electron-transfer chain. A PS II reaction center complex (E-1) which has 47, 40, 31, 28 and 9 kDa subunits shows both fast decaying (signal IIf) and slowly decaying (signal IIs+u) EPR components. The amplitude of signal IIf, which represents Z (the donor to P-680), is about 1 spin per 30 Chl. This corresponds to one spin per reaction center in this preparation. Signal IIs+u, the slowly decaying component of signal II, reflects D, a donor to PS II on a side chain from the path of water oxidation in higher plants and algae. Signal IIs+u is present in the E-1 preparation in a ratio of about 1 spin per 40 Chl. Flash-induced signal IIf in E-1 shows biexponential decay with half-times of 20 ms and 300 ms. In a PS II reaction center complex (CP2b) which has 47, 31, 28 and 9 kDa subunits, but no 40 kDa subunit, an appreciable amount of signal IIf is observed (about 1 per 50 Chl). Less than 1 spin per 400 Chl of signal IIs+u is visible in this sample. The kinetics of Z+ reduction (signal IIf) in CP2b is similar to that seen in E-1 preparations, indicating that CP2b contains all of the molecules necessary for primary charge separation and secondary electron donation from Z.

Original languageEnglish (US)
Pages (from-to)226-233
Number of pages8
JournalBBA - Bioenergetics
Volume850
Issue number2
DOIs
StatePublished - Jul 2 1986

Keywords

  • (Cyanobacterium
  • ESR
  • Electron transfer
  • Photosynthesis
  • Photosystem II
  • Signal II
  • Synechococcus)

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology

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