Abstract
In Photosystem II (PS II), a non-heme iron is present near the electron-accepting quinones QA and QB. A putative ligand to this non-heme iron, His-268 in the D2 protein, was mutated to Gln in the cyanobacterium Synechocystis sp. PCC 6803. The resulting mutant H268Q has lost photoautotrophic capacity and shows large alterations in the properties both of QA and of the QB pocket. In the mutant, the quantum efficiency of QA reduction is decreased by approximately 50-fold, electron transfer from QA to the plastoquinone pool is blocked, QA apparently can be displaced by exogenous quinones, and the stability of reduced QA is increased by more than an order of magnitude. Also the affinity of the PS II-directed herbicide diuron to the PS II complex is decreased to undetectable levels. We suggest that these mutation-induced changes in the properties of the acceptor side of PS II are caused by a functional loss of the non-heme iron. This would imply that the non-heme iron in PS II plays a functionally more important role than observed in reaction centers from purple bacteria, and has drastic effects on the properties of QA. Moreover, the results obtained on the D2 mutant H268Q illustrate that the D2 protein can have a pronounced influence on the properties of the QB/herbicide-binding environment, which is associated mostly with the D1 protein. Thus, the non-heme iron in PS II appears to both affect QA reactivity and alter the properties of the QB pocket.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 263-272 |
| Number of pages | 10 |
| Journal | BBA - Bioenergetics |
| Volume | 1184 |
| Issue number | 2-3 |
| DOIs | |
| State | Published - Mar 8 1994 |
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Keywords
- Cyanobacterium
- Iron
- Non-heme iron
- Photosynthesis
- Photosystem II
- Quinone
- Reaction center
ASJC Scopus subject areas
- Biophysics
Cite this
Mutation of a putative ligand to the non-heme iron in Photosystem II : implications for QA reactivity, electron transfer, and herbicide binding. / Vermaas, Willem; Vass, Imre; Eggers, Beth; Styring, Stenbjörn.
In: BBA - Bioenergetics, Vol. 1184, No. 2-3, 08.03.1994, p. 263-272.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Mutation of a putative ligand to the non-heme iron in Photosystem II
T2 - implications for QA reactivity, electron transfer, and herbicide binding
AU - Vermaas, Willem
AU - Vass, Imre
AU - Eggers, Beth
AU - Styring, Stenbjörn
PY - 1994/3/8
Y1 - 1994/3/8
N2 - In Photosystem II (PS II), a non-heme iron is present near the electron-accepting quinones QA and QB. A putative ligand to this non-heme iron, His-268 in the D2 protein, was mutated to Gln in the cyanobacterium Synechocystis sp. PCC 6803. The resulting mutant H268Q has lost photoautotrophic capacity and shows large alterations in the properties both of QA and of the QB pocket. In the mutant, the quantum efficiency of QA reduction is decreased by approximately 50-fold, electron transfer from QA to the plastoquinone pool is blocked, QA apparently can be displaced by exogenous quinones, and the stability of reduced QA is increased by more than an order of magnitude. Also the affinity of the PS II-directed herbicide diuron to the PS II complex is decreased to undetectable levels. We suggest that these mutation-induced changes in the properties of the acceptor side of PS II are caused by a functional loss of the non-heme iron. This would imply that the non-heme iron in PS II plays a functionally more important role than observed in reaction centers from purple bacteria, and has drastic effects on the properties of QA. Moreover, the results obtained on the D2 mutant H268Q illustrate that the D2 protein can have a pronounced influence on the properties of the QB/herbicide-binding environment, which is associated mostly with the D1 protein. Thus, the non-heme iron in PS II appears to both affect QA reactivity and alter the properties of the QB pocket.
AB - In Photosystem II (PS II), a non-heme iron is present near the electron-accepting quinones QA and QB. A putative ligand to this non-heme iron, His-268 in the D2 protein, was mutated to Gln in the cyanobacterium Synechocystis sp. PCC 6803. The resulting mutant H268Q has lost photoautotrophic capacity and shows large alterations in the properties both of QA and of the QB pocket. In the mutant, the quantum efficiency of QA reduction is decreased by approximately 50-fold, electron transfer from QA to the plastoquinone pool is blocked, QA apparently can be displaced by exogenous quinones, and the stability of reduced QA is increased by more than an order of magnitude. Also the affinity of the PS II-directed herbicide diuron to the PS II complex is decreased to undetectable levels. We suggest that these mutation-induced changes in the properties of the acceptor side of PS II are caused by a functional loss of the non-heme iron. This would imply that the non-heme iron in PS II plays a functionally more important role than observed in reaction centers from purple bacteria, and has drastic effects on the properties of QA. Moreover, the results obtained on the D2 mutant H268Q illustrate that the D2 protein can have a pronounced influence on the properties of the QB/herbicide-binding environment, which is associated mostly with the D1 protein. Thus, the non-heme iron in PS II appears to both affect QA reactivity and alter the properties of the QB pocket.
KW - Cyanobacterium
KW - Iron
KW - Non-heme iron
KW - Photosynthesis
KW - Photosystem II
KW - Quinone
KW - Reaction center
UR - http://www.scopus.com/inward/record.url?scp=0028175446&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0028175446&partnerID=8YFLogxK
U2 - 10.1016/0005-2728(94)90231-3
DO - 10.1016/0005-2728(94)90231-3
M3 - Article
VL - 1184
SP - 263
EP - 272
JO - Biochimica et Biophysica Acta - Bioenergetics
JF - Biochimica et Biophysica Acta - Bioenergetics
SN - 0005-2728
IS - 2-3
ER -