Abstract
In intact PSII, both the secondary electron donor (TyrZ) and side-path electron donors (Car/ChlZ/Cytb559) can be oxidized by P680 +{radical dot} at cryogenic temperatures. In this paper, the effects of acceptor side, especially the redox state of the non-heme iron, on the donor side electron transfer induced by visible light at cryogenic temperatures were studied by EPR spectroscopy. We found that the formation and decay of the S1TyrZ{radical dot} EPR signal were independent of the treatment of K3Fe(CN)6, whereas formation and decay of the Car+{radical dot}/ChlZ +{radical dot} EPR signal correlated with the reduction and recovery of the Fe3+ EPR signal of the non-heme iron in K3Fe(CN)6 pre-treated PSII, respectively. Based on the observed correlation between Car/ChlZ oxidation and Fe3+ reduction, the oxidation of non-heme iron by K3Fe(CN)6 at 0 °C was quantified, which showed that around 50-60% fractions of the reaction centers gave rise to the Fe3+ EPR signal. In addition, we found that the presence of phenyl-p-benzoquinone significantly enhanced the yield of TyrZ oxidation. These results indicate that the electron transfer at the donor side can be significantly modified by changes at the acceptor side, and indicate that two types of reaction centers are present in intact PSII, namely, one contains unoxidizable non-heme iron and another one contains oxidizable non-heme iron. TyrZ oxidation and side-path reaction occur separately in these two types of reaction centers, instead of competition with each other in the same reaction centers. In addition, our results show that the non-heme iron has different properties in active and inactive PSII. The oxidation of non-heme iron by K3Fe(CN)6 takes place only in inactive PSII, which implies that the Fe3+ state is probably not the intermediate species for the turnover of quinone reduction.
| Original language | English |
|---|---|
| Pages (from-to) | 1109-1115 |
| Number of pages | 7 |
| Journal | Biochimica et Biophysica Acta - Bioenergetics |
| Volume | 1777 |
| Issue number | 9 |
| DOIs | |
| Publication status | Published - Sep 2008 |
| Externally published | Yes |
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Keywords
- Electron transfer
- EPR
- Non-heme iron
- Photosystem II
- Side-path electron donor
- Tyr
ASJC Scopus subject areas
- Biophysics
Cite this
Acceptor side effects on the electron transfer at cryogenic temperatures in intact photosystem II. / Bao, Han; Zhang, Chunxi; Kawakami, Keisuke; Ren, Yanan; Shen, Jian-Ren; Zhao, Jingquan.
In: Biochimica et Biophysica Acta - Bioenergetics, Vol. 1777, No. 9, 09.2008, p. 1109-1115.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Acceptor side effects on the electron transfer at cryogenic temperatures in intact photosystem II
AU - Bao, Han
AU - Zhang, Chunxi
AU - Kawakami, Keisuke
AU - Ren, Yanan
AU - Shen, Jian-Ren
AU - Zhao, Jingquan
PY - 2008/9
Y1 - 2008/9
N2 - In intact PSII, both the secondary electron donor (TyrZ) and side-path electron donors (Car/ChlZ/Cytb559) can be oxidized by P680 +{radical dot} at cryogenic temperatures. In this paper, the effects of acceptor side, especially the redox state of the non-heme iron, on the donor side electron transfer induced by visible light at cryogenic temperatures were studied by EPR spectroscopy. We found that the formation and decay of the S1TyrZ{radical dot} EPR signal were independent of the treatment of K3Fe(CN)6, whereas formation and decay of the Car+{radical dot}/ChlZ +{radical dot} EPR signal correlated with the reduction and recovery of the Fe3+ EPR signal of the non-heme iron in K3Fe(CN)6 pre-treated PSII, respectively. Based on the observed correlation between Car/ChlZ oxidation and Fe3+ reduction, the oxidation of non-heme iron by K3Fe(CN)6 at 0 °C was quantified, which showed that around 50-60% fractions of the reaction centers gave rise to the Fe3+ EPR signal. In addition, we found that the presence of phenyl-p-benzoquinone significantly enhanced the yield of TyrZ oxidation. These results indicate that the electron transfer at the donor side can be significantly modified by changes at the acceptor side, and indicate that two types of reaction centers are present in intact PSII, namely, one contains unoxidizable non-heme iron and another one contains oxidizable non-heme iron. TyrZ oxidation and side-path reaction occur separately in these two types of reaction centers, instead of competition with each other in the same reaction centers. In addition, our results show that the non-heme iron has different properties in active and inactive PSII. The oxidation of non-heme iron by K3Fe(CN)6 takes place only in inactive PSII, which implies that the Fe3+ state is probably not the intermediate species for the turnover of quinone reduction.
AB - In intact PSII, both the secondary electron donor (TyrZ) and side-path electron donors (Car/ChlZ/Cytb559) can be oxidized by P680 +{radical dot} at cryogenic temperatures. In this paper, the effects of acceptor side, especially the redox state of the non-heme iron, on the donor side electron transfer induced by visible light at cryogenic temperatures were studied by EPR spectroscopy. We found that the formation and decay of the S1TyrZ{radical dot} EPR signal were independent of the treatment of K3Fe(CN)6, whereas formation and decay of the Car+{radical dot}/ChlZ +{radical dot} EPR signal correlated with the reduction and recovery of the Fe3+ EPR signal of the non-heme iron in K3Fe(CN)6 pre-treated PSII, respectively. Based on the observed correlation between Car/ChlZ oxidation and Fe3+ reduction, the oxidation of non-heme iron by K3Fe(CN)6 at 0 °C was quantified, which showed that around 50-60% fractions of the reaction centers gave rise to the Fe3+ EPR signal. In addition, we found that the presence of phenyl-p-benzoquinone significantly enhanced the yield of TyrZ oxidation. These results indicate that the electron transfer at the donor side can be significantly modified by changes at the acceptor side, and indicate that two types of reaction centers are present in intact PSII, namely, one contains unoxidizable non-heme iron and another one contains oxidizable non-heme iron. TyrZ oxidation and side-path reaction occur separately in these two types of reaction centers, instead of competition with each other in the same reaction centers. In addition, our results show that the non-heme iron has different properties in active and inactive PSII. The oxidation of non-heme iron by K3Fe(CN)6 takes place only in inactive PSII, which implies that the Fe3+ state is probably not the intermediate species for the turnover of quinone reduction.
KW - Electron transfer
KW - EPR
KW - Non-heme iron
KW - Photosystem II
KW - Side-path electron donor
KW - Tyr
UR - http://www.scopus.com/inward/record.url?scp=49349105209&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=49349105209&partnerID=8YFLogxK
U2 - 10.1016/j.bbabio.2008.04.044
DO - 10.1016/j.bbabio.2008.04.044
M3 - Article
C2 - 18510941
AN - SCOPUS:49349105209
VL - 1777
SP - 1109
EP - 1115
JO - Biochimica et Biophysica Acta - Bioenergetics
JF - Biochimica et Biophysica Acta - Bioenergetics
SN - 0005-2728
IS - 9
ER -