Electron spin resonance studies of the bound iron-sulfur centers in Photosystem I. Photoreduction of center A occurs in the absence of center B

John H. Golbeck, Joseph T. Warden

Research output: Contribution to journalArticle

34 Scopus citations

Abstract

The Photosystem I acceptor system of a subchloroplast particle from spinach was investigated by optical and electron spin resonance (ESR) spectroscopy following graduated inactivation of the bound iron-sulfur proteins by urea/ferricyanide solution. The chemical analysis of iron and sulfur and the ESR properties of centers A, B and X are consistent with the participation of three iron-sulfur centers in Photosystem I. A differential decrease in centers A, B and X is observed under conditions that induce S2- →S0 conversion in the bound iron-sulfur proteins. Center B is shown to be the most susceptible, while center 'X' is the least susceptible component to oxidative denaturation. Stepwise inactivation experiments suggest that electron transport in Photosystem I does not occur sequentially from X→B→A, since there is quantitative photoreduction of center A in the absence of center B. We propose that center A is directly reduced by X; thus, X may serve as a branch point for parallel electron flow through centers A and B.

Original languageEnglish (US)
Pages (from-to)77-84
Number of pages8
JournalBBA - Bioenergetics
Volume681
Issue number1
DOIs
StatePublished - Jul 22 1982

All Science Journal Classification (ASJC) codes

  • Biophysics
  • Biochemistry
  • Cell Biology

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