Open AccessElectron paramagnetic resonance studies of photosynthetic electron transport: Photoreduction of ferredoxin and membrane-bound iron-sulfur centers
Author(s) -
Daniel I. Ar,
Harry Y. Tsujimoto,
Tetsuo Hiyama
Publication year - 1977
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.74.9.3826
Subject(s) - ferredoxin , electron paramagnetic resonance , electron transport chain , chemistry , photochemistry , bound water , photosynthetic reaction centre , sulfur , redox , membrane , photosystem i , electron transfer , photosynthesis , nuclear magnetic resonance , inorganic chemistry , biochemistry , molecule , physics , photosystem ii , organic chemistry , enzyme
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.