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Title: Effect Of Calcium Chelators on the Formation and Oxidation of the Slowly Relaxing Reduced Plastoquinone Pool in Calcium-Depleted PSII Membranes. Investigation of the F0 Yield

Abstract

The F{sub 0} fluorescence yield in intact photosystem II (PSII), Ca-depleted PSII (PSII(-Ca/NaCl)), and Mn-depleted PSII membranes was measured before and after dim light treatment (1-2 min), using flash-probe fluorescence and fluorescence induction kinetic measurements. The value of F{sub 0} after the light treatment (F{sup '}{sub 0}) was larger than F{sub 0} in dark-adapted PSII membranes and depended on the appearance of the slowly relaxing, reduced plastoquinone pool (t{sub 1/2} = 4 min) formed during preillumination, which was not totally reoxidized before the F{sup '}{sub 0} measurement. In PSII(-Ca/NaCl) such a pool also appeared, but the F{sup '}{sub 0} yield was even higher than in intact PSII membranes. In Mn-depleted PSII membranes, the pool did not form. Interestingly, the yield of F{sup '}{sub 0} in Ca-depleted PSII membranes prepared using chelators (EGTA and citrate) or containing 5 mM EGTA was significantly lower than in PSII(-Ca/NaCl) samples prepared without chelators. These data indicate that chelators inhibit the reduction of QA and QB and formation of the slowly relaxing plastoquinone pool, or alternatively they increase the rate of its oxidation. Such an effect can be explained by coordination of the chelator molecule to the Mn cluster in PSII(-Ca/NaCl) membranes, rather than differentmore » amounts of residual Ca{sup 2+} in the membranes (with or without the chelator), since the remaining oxygen-evolving activity ({approx}15%) in PSII(-Ca/NaCl) samples did not depend on the presence of the chelator. Thus, chelators of calcium cations not only have an effect on the EPR properties of the S2 state in PSII(-Ca/NaCl) samples, but can also influence the PSII properties determining the rate of plastoquinone pool reduction and/or oxidation. The effect of some toxic metal cations (Cd, Cu, Hg) on the formation of the slowly relaxing pool in PSII membranes was also studied.« less

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
982267
DOE Contract Number:  
AC36-08GO28308
Resource Type:
Journal Article
Resource Relation:
Journal Name: Biochemistry (Moscow); Journal Volume: 72; Journal Issue: 11, 2007
Country of Publication:
United States
Language:
English
Subject:
09 BIOMASS FUELS; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 59 BASIC BIOLOGICAL SCIENCES; CALCIUM; CATIONS; DATA; EGTA; ELECTRON SPIN RESONANCE; FLUORESCENCE; INDUCTION; KINETICS; MEMBRANES; METALS; METHYL METHANESULFONATE; MOLECULES; OXIDATION; PLASTOQUINONE; PONDS; REDUCTION; VISIBLE RADIATION; YIELDS; Energy Sciences; Photoconversion

Citation Formats

Semin, B. K., Davletshina, L. N., Bulychev, A. A., Ivanov, I. I., Seibert, M., and Rubin, A. B. Effect Of Calcium Chelators on the Formation and Oxidation of the Slowly Relaxing Reduced Plastoquinone Pool in Calcium-Depleted PSII Membranes. Investigation of the F0 Yield. United States: N. p., 2007. Web. doi:10.1134/S0006297907110065.
Semin, B. K., Davletshina, L. N., Bulychev, A. A., Ivanov, I. I., Seibert, M., & Rubin, A. B. Effect Of Calcium Chelators on the Formation and Oxidation of the Slowly Relaxing Reduced Plastoquinone Pool in Calcium-Depleted PSII Membranes. Investigation of the F0 Yield. United States. doi:10.1134/S0006297907110065.
Semin, B. K., Davletshina, L. N., Bulychev, A. A., Ivanov, I. I., Seibert, M., and Rubin, A. B. Mon . "Effect Of Calcium Chelators on the Formation and Oxidation of the Slowly Relaxing Reduced Plastoquinone Pool in Calcium-Depleted PSII Membranes. Investigation of the F0 Yield". United States. doi:10.1134/S0006297907110065.
@article{osti_982267,
title = {Effect Of Calcium Chelators on the Formation and Oxidation of the Slowly Relaxing Reduced Plastoquinone Pool in Calcium-Depleted PSII Membranes. Investigation of the F0 Yield},
author = {Semin, B. K. and Davletshina, L. N. and Bulychev, A. A. and Ivanov, I. I. and Seibert, M. and Rubin, A. B.},
abstractNote = {The F{sub 0} fluorescence yield in intact photosystem II (PSII), Ca-depleted PSII (PSII(-Ca/NaCl)), and Mn-depleted PSII membranes was measured before and after dim light treatment (1-2 min), using flash-probe fluorescence and fluorescence induction kinetic measurements. The value of F{sub 0} after the light treatment (F{sup '}{sub 0}) was larger than F{sub 0} in dark-adapted PSII membranes and depended on the appearance of the slowly relaxing, reduced plastoquinone pool (t{sub 1/2} = 4 min) formed during preillumination, which was not totally reoxidized before the F{sup '}{sub 0} measurement. In PSII(-Ca/NaCl) such a pool also appeared, but the F{sup '}{sub 0} yield was even higher than in intact PSII membranes. In Mn-depleted PSII membranes, the pool did not form. Interestingly, the yield of F{sup '}{sub 0} in Ca-depleted PSII membranes prepared using chelators (EGTA and citrate) or containing 5 mM EGTA was significantly lower than in PSII(-Ca/NaCl) samples prepared without chelators. These data indicate that chelators inhibit the reduction of QA and QB and formation of the slowly relaxing plastoquinone pool, or alternatively they increase the rate of its oxidation. Such an effect can be explained by coordination of the chelator molecule to the Mn cluster in PSII(-Ca/NaCl) membranes, rather than different amounts of residual Ca{sup 2+} in the membranes (with or without the chelator), since the remaining oxygen-evolving activity ({approx}15%) in PSII(-Ca/NaCl) samples did not depend on the presence of the chelator. Thus, chelators of calcium cations not only have an effect on the EPR properties of the S2 state in PSII(-Ca/NaCl) samples, but can also influence the PSII properties determining the rate of plastoquinone pool reduction and/or oxidation. The effect of some toxic metal cations (Cd, Cu, Hg) on the formation of the slowly relaxing pool in PSII membranes was also studied.},
doi = {10.1134/S0006297907110065},
journal = {Biochemistry (Moscow)},
number = 11, 2007,
volume = 72,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}