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. 1997 Jan;72(1):301–315. doi: 10.1016/S0006-3495(97)78669-7

Near-IR absorbance changes and electrogenic reactions in the microsecond-to-second time domain in Photosystem I.

I R Vassiliev 1, Y S Jung 1, M D Mamedov 1, Semenov AYu 1, J H Golbeck 1
PMCID: PMC1184319  PMID: 8994615

Abstract

The back-reaction kinetics in Photosystem I (PS I) were studied on the microsecond-to-s time scale in cyanobacterial preparations, which differed in the number of iron-sulfur clusters to assess the contributions of particular components to the reduction of P700+. In membrane fragments and in trimeric P700-FA/FB complexes, the major contribution to the absorbance change at 820 nm (delta A820) was the back-reaction of FA- and/or FB- with lifetimes of approximately 10 and 80 ms (approximately 10% and 40% relative amplitude). The decay of photoinduced electric potential (delta psi) across a membrane with directionally incorporated P700-FA/FB complexes had similar kinetics. HgCl2-treated PS I complexes, which contain FA but no FB, retain both of these kinetic components, indicating that neither can be assigned uniquely to a specific acceptor. These results suggest that FA- reduces P700+ directly and argue for a rapid electron equilibration between FA and FB, which would eliminate their kinetic distinction in a back-reaction. In PsaC-depleted P700-Fx cores, as well as in P700-FA/FB complexes with chemically reduced FA and FB, the major contribution to the delta A820 and the delta psi decay is a biphasic back-reaction of F-X (approximately 400 microseconds and 1.5 ms) with some contribution from A-1 (approximately 10 microseconds and 100 microseconds), the latter of which is variable depending on experimental conditions. The delta A820 decay in a P700-A1 core devoid of all iron-sulfur clusters comprises two phases with lifetimes of 10 microseconds and 130 microseconds (2.7:1 ratio). The biexponential back-reaction kinetics found for each of the electron acceptors may be related to existence of different conformational states of the PS I complex. In all preparations studied, excitation at 532 nm with flash energies exceeding 10 mJ gives rise to formation of antenna 3Chl, which also contributes to delta A820 decay on the tens-of-microsecond time scale. A distinction between delta A820 components related to back-reactions and to 3Chl decay can be made by analysis of flash saturation dependencies and by measurements of kinetics with preoxidized P700.

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Selected References

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  1. Anderson S. L., McIntosh L. Partial conservation of the 5' ndhE-psaC-ndhD 3' gene arrangement of chloroplasts in the cyanobacterium Synechocystis sp. PCC 6803: implications for NDH-D function in cyanobacteria and chloroplasts. Plant Mol Biol. 1991 Apr;16(4):487–499. doi: 10.1007/BF00023416. [DOI] [PubMed] [Google Scholar]
  2. Drachev L. A., Kaulen A. D., Semenov A. Y., Severina I. I., Skulachev V. P. Lipid-impregnated filters as a tool for studying the electric current-generating proteins. Anal Biochem. 1979 Jul 1;96(1):250–262. doi: 10.1016/0003-2697(79)90580-3. [DOI] [PubMed] [Google Scholar]
  3. Hastings G., Hoshina S., Webber A. N., Blankenship R. E. Universality of energy and electron transfer processes in photosystem I. Biochemistry. 1995 Nov 28;34(47):15512–15522. doi: 10.1021/bi00047a017. [DOI] [PubMed] [Google Scholar]
  4. Hiyama T., Ke B. Difference spectra and extinction coefficients of P 700 . Biochim Biophys Acta. 1972 Apr 20;267(1):160–171. doi: 10.1016/0005-2728(72)90147-8. [DOI] [PubMed] [Google Scholar]
  5. Ke B. One-way electron discharge subsequent to the photochemical charge separation in photosystem I. Biochim Biophys Acta. 1972 Jun 23;267(3):595–599. doi: 10.1016/0005-2728(72)90192-2. [DOI] [PubMed] [Google Scholar]
  6. Leibl W., Toupance B., Breton J. Photoelectric characterization of forward electron transfer to iron-sulfur centers in photosystem I. Biochemistry. 1995 Aug 15;34(32):10237–10244. doi: 10.1021/bi00032a018. [DOI] [PubMed] [Google Scholar]
  7. Li N., Warren P. V., Golbeck J. H., Frank G., Zuber H., Bryant D. A. Polypeptide composition of the Photosystem I complex and the Photosystem I core protein from Synechococcus sp. PCC 6301. Biochim Biophys Acta. 1991 Aug 23;1059(2):215–225. doi: 10.1016/s0005-2728(05)80206-3. [DOI] [PubMed] [Google Scholar]
  8. Lüneberg J., Fromme P., Jekow P., Schlodder E. Spectroscopic characterization of PS I core complexes from thermophilic Synechococcus sp. Identical reoxidation kinetics of A1- before and after removal of the iron-sulfur-clusters FA and FB. FEBS Lett. 1994 Jan 31;338(2):197–202. doi: 10.1016/0014-5793(94)80364-1. [DOI] [PubMed] [Google Scholar]
  9. Parrett K. G., Mehari T., Warren P. G., Golbeck J. H. Purification and properties of the intact P-700 and Fx-containing Photosystem I core protein. Biochim Biophys Acta. 1989 Feb 28;973(2):324–332. doi: 10.1016/s0005-2728(89)80439-6. [DOI] [PubMed] [Google Scholar]
  10. Rodday S. M., Webber A. N., Bingham S. E., Biggins J. Evidence that the FX domain in photosystem I interacts with the subunit PsaC: site-directed changes in PsaB destabilize the subunit interaction in Chlamydomonas reinhardtii. Biochemistry. 1995 May 16;34(19):6328–6334. doi: 10.1021/bi00019a010. [DOI] [PubMed] [Google Scholar]
  11. Sauer K., Mathis P., Acker S., van Best J. A. Absorption changes of P-700 reversible in milliseconds at low temperature in Triton-solubilized photosystem I particles. Biochim Biophys Acta. 1979 Mar 15;545(3):466–472. doi: 10.1016/0005-2728(79)90155-5. [DOI] [PubMed] [Google Scholar]
  12. Sauer K., Mathis P., Acker S., van Best J. A. Electron acceptors associated with P-700 in Triton solubilized photosystem I particles from spinach chloroplasts. Biochim Biophys Acta. 1978 Jul 6;503(1):120–134. doi: 10.1016/0005-2728(78)90166-4. [DOI] [PubMed] [Google Scholar]
  13. Sigfridsson K., Hansson O., Brzezinski P. Electrogenic light reactions in photosystem I: resolution of electron-transfer rates between the iron-sulfur centers. Proc Natl Acad Sci U S A. 1995 Apr 11;92(8):3458–3462. doi: 10.1073/pnas.92.8.3458. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Smart L. B., Anderson S. L., McIntosh L. Targeted genetic inactivation of the photosystem I reaction center in the cyanobacterium Synechocystis sp. PCC 6803. EMBO J. 1991 Nov;10(11):3289–3296. doi: 10.1002/j.1460-2075.1991.tb04893.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Sétif P., Brettel K. Forward electron transfer from phylloquinone A1 to iron-sulfur centers in spinach photosystem I. Biochemistry. 1993 Aug 10;32(31):7846–7854. doi: 10.1021/bi00082a002. [DOI] [PubMed] [Google Scholar]
  16. Vassiliev I. R., Jung Y. S., Smart L. B., Schulz R., McIntosh L., Golbeck J. H. A mixed-ligand iron-sulfur cluster (C556SPaB or C565SPsaB) in the Fx-binding site leads to a decreased quantum efficiency of electron transfer in photosystem I. Biophys J. 1995 Oct;69(4):1544–1553. doi: 10.1016/S0006-3495(95)80026-3. [DOI] [PMC free article] [PubMed] [Google Scholar]
  17. Warren P. V., Golbeck J. H., Warden J. T. Charge recombination between P700+ and A1- occurs directly to the ground state of P700 in a photosystem I core devoid of FX, FB, and FA. Biochemistry. 1993 Jan 26;32(3):849–857. doi: 10.1021/bi00054a016. [DOI] [PubMed] [Google Scholar]
  18. Warren P. V., Parrett K. G., Warden J. T., Golbeck J. H. Characterization of a photosystem I core containing P700 and intermediate electron acceptor A1. Biochemistry. 1990 Jul 17;29(28):6545–6550. doi: 10.1021/bi00480a001. [DOI] [PubMed] [Google Scholar]

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