TY - JOUR
T1 - Redox potential of pheophytin a in photosystem II of two cyanobacteria having the different special pair chlorophylls
AU - Allakhverdiev, Suleyman
AU - Tomo, Tatsuya
AU - Shimada, Yuichiro
AU - Kindo, Hayato
AU - Nagao, Ryo
AU - Klimov, Vyacheslav V.
AU - Mimuro, Mamoru
PY - 2010/2/23
Y1 - 2010/2/23
N2 - Water oxidation by photosystem (PS) II in oxygenic photosynthetic organisms is a major source of energy on the earth, leading to the production of a stable reductant. Mechanisms generating a high oxidation potential for water oxidation have been a major focus of photosynthesis research. This potential has not been estimated directly but has been measured by the redox potential of the primary electron acceptor, pheophytin (Phe) a.However, the reported values for Phe a are still controversial. Here,we measured the redox potential of Phe a under physiological conditions (pH 7.0; 25 °C) in two cyanobacteria with different special pair chlorophylls (Chls): Synechocystis sp. PCC 6803, whose special pair for PS II consists of Chl a, and Acaryochloris marina MBIC 11017, whose special pair for PS II consists of Chl d.We obtained redox potentials of -536 ± 8 mV for Synechocystis sp. PCC 6803 and -478 ± 24 mV for A. marina on PS II complexes in the presence of 1.0 M betaine. The difference in the redox potential of Phe a between the two species closely corresponded with the difference in the light energy absorbed by Chl a versus Chld.We estimated the potentials of the special pair of PS II to be 1.20 V and 1.18 V for Synechocystis sp. PCC 6803 (P680) and A. marina (P713), respectively. This clearly indicates conservation in the properties of water-oxidation systems in oxygenic photosynthetic organisms, irrespective of the special-pair chlorophylls.
AB - Water oxidation by photosystem (PS) II in oxygenic photosynthetic organisms is a major source of energy on the earth, leading to the production of a stable reductant. Mechanisms generating a high oxidation potential for water oxidation have been a major focus of photosynthesis research. This potential has not been estimated directly but has been measured by the redox potential of the primary electron acceptor, pheophytin (Phe) a.However, the reported values for Phe a are still controversial. Here,we measured the redox potential of Phe a under physiological conditions (pH 7.0; 25 °C) in two cyanobacteria with different special pair chlorophylls (Chls): Synechocystis sp. PCC 6803, whose special pair for PS II consists of Chl a, and Acaryochloris marina MBIC 11017, whose special pair for PS II consists of Chl d.We obtained redox potentials of -536 ± 8 mV for Synechocystis sp. PCC 6803 and -478 ± 24 mV for A. marina on PS II complexes in the presence of 1.0 M betaine. The difference in the redox potential of Phe a between the two species closely corresponded with the difference in the light energy absorbed by Chl a versus Chld.We estimated the potentials of the special pair of PS II to be 1.20 V and 1.18 V for Synechocystis sp. PCC 6803 (P680) and A. marina (P713), respectively. This clearly indicates conservation in the properties of water-oxidation systems in oxygenic photosynthetic organisms, irrespective of the special-pair chlorophylls.
KW - Betaine
KW - Chlorophyll d
KW - Oxygen evolution
KW - Photosynthesis
KW - Redox titration
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U2 - 10.1073/pnas.0913460107
DO - 10.1073/pnas.0913460107
M3 - Article
C2 - 20142495
AN - SCOPUS:77649324572
SN - 0027-8424
VL - 107
SP - 3924
EP - 3929
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 8
ER -