TY - JOUR
T1 - Electron spin resonance studies of the bound iron-sulfur centers in Photosystem I. Photoreduction of center A occurs in the absence of center B
AU - Golbeck, John H.
AU - Warden, Joseph T.
N1 - Funding Information:
We thank Mr. Kirk Cammarata for excellent technical assistance. This work was funded in part by the United States Department of Energy (DE-AC02-76ER03326) (J.H.G.) and by the Science and Education Administration of the U.S.' Department of Agriculture under Grant No. 590,1~0410-8-0073-0 from the Competitive Grants Office (J.T.W.).
PY - 1982/7/22
Y1 - 1982/7/22
N2 - 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.
AB - 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.
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U2 - 10.1016/0005-2728(82)90280-8
DO - 10.1016/0005-2728(82)90280-8
M3 - Article
AN - SCOPUS:49049134879
VL - 681
SP - 77
EP - 84
JO - Biochimica et Biophysica Acta - Bioenergetics
JF - Biochimica et Biophysica Acta - Bioenergetics
SN - 0005-2728
IS - 1
ER -