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Proceedings of the National Academy of Sciences of the United States of America logoLink to Proceedings of the National Academy of Sciences of the United States of America
. 1977 Sep;74(9):3826–3830. doi: 10.1073/pnas.74.9.3826

Electron paramagnetic resonance studies of photosynthetic electron transport: Photoreduction of ferredoxin and membrane-bound iron-sulfur centers*

Daniel I Arnon 1, Harry Y Tsujimoto 1, Tetsuo Hiyama 1
PMCID: PMC431747  PMID: 198808

Abstract

Electron paramagnetic resonance spectrometry was used to investigate, at physiological temperatures, light-induced electron transport from membrane-bound iron-sulfur components (bound ferredoxin) to soluble ferredoxin and NADP+ in membrane fragments (from the blue-green alga, Nostoc muscorum) that had high rates of electron transport from water to NADP+ and from an artificial electron donor, reduced dichlorophenolindophenol (DCIPH2) to NADP+. Illumination at 20° resulted in the photoreduction of membrane-bound iron-sulfur centers A and B. Photoreduction by water gave electron paramagnetic resonance signals of both centers A and B; photoreduction by DCIPH2 was found to generate a strong electron paramagnetic signal of only center B.

When water was the reductant, the addition and photoreduction of soluble ferredoxin generated additional signals characteristics of soluble ferredoxin without causing a decrease in the amplitude of the signals due to centers A and B. The further addition of NADP+ (and its photoreduction) greatly diminished signals due to the bound iron-sulfur centers and to soluble ferredoxin. An outflow of electrons from center B to soluble ferredoxin and NADP+ was particularly pronounced when DCIPH2 was the reductant. These observations provide the first evidence for a light-induced electron transport between membrane-bound iron-sulfur centers and ferredoxin-NADP+. The relationship of these observations to current concepts of photosynthetic electron transport is discussed.

Keywords: photosynthesis, reducing power, electron carriers

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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