Alteration of the axial met ligand to electron acceptor A0 in photosystem I

Effect on the generation of P700 ·+ A1 ·- radical pairs as studied by W-band transient EPR

Anton Savitsky, Oksana Gopta, Mahir Mamedov, John H. Golbeck, Alexander Tikhonov, Klaus Möbius, Alexey Semenov

Research output: Contribution to journalArticle

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Abstract

Photosystem I (PS I) mutants from the cyanobacterium Synechocystis sp. PCC 6803 bearing point mutations to the axial ligands of A0A (M688NPsaA) and A0B (M668NPsaB) were studied by high-field W-band electron paramagnetic resonance (EPR) spectroscopy. It was found that the EPR observables of PS I from the M668NPsaB mutant were virtual identical to that of the wild type (WT), and are clearly distinct from the M688NPsaA mutant. In particular, the P700 ·+ decay kinetics in the M688NPsaA mutant is significantly slower than in the WT or the M668NPsaB mutant. The analysis of the out-of-phase electron-electron dipolar electron spin echo envelope modulation shows that in the M668NPsaB mutant, the estimated distance of 26.0 ± 0.3 Å agrees well with the 25.8 Å distance for the P700 ·+A1A ·- radical pair measured in the X-ray crystal structure. In the M688NPsaA mutant, two populations are found with estimated distances of 26.0 ± 0.3 and 25.0 ± 0.3 Å in a ratio of 0.7-0.3, which agree well with the 25.8 Å distance for the P700 ·+A1A ·- radical pair and the 24.6 Å distance for the P700 ·+A1B ·- radical pair measured in the X-ray crystal structure. The data confirm that under the experimental conditions employed in this work, which involve dark-adapted samples without the pre-reduction of the iron-sulfur clusters, electron transport in cyanobacterial PS I is asymmetrical at 100 K, with the majority of electron transfer taking place through the A-branch of cofactors.

Original languageEnglish
Pages (from-to)85-102
Number of pages18
JournalApplied Magnetic Resonance
Volume37
Issue number1
DOIs
Publication statusPublished - 2010
Externally publishedYes

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electron paramagnetic resonance
ligands
electrons
crystal structure
mutations
electron spin
echoes
electron transfer
x rays
sulfur
envelopes
modulation
iron
kinetics
decay
spectroscopy

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

Cite this

Alteration of the axial met ligand to electron acceptor A0 in photosystem I : Effect on the generation of P700 ·+ A1 ·- radical pairs as studied by W-band transient EPR. / Savitsky, Anton; Gopta, Oksana; Mamedov, Mahir; Golbeck, John H.; Tikhonov, Alexander; Möbius, Klaus; Semenov, Alexey.

In: Applied Magnetic Resonance, Vol. 37, No. 1, 2010, p. 85-102.

Research output: Contribution to journalArticle

Savitsky, Anton ; Gopta, Oksana ; Mamedov, Mahir ; Golbeck, John H. ; Tikhonov, Alexander ; Möbius, Klaus ; Semenov, Alexey. / Alteration of the axial met ligand to electron acceptor A0 in photosystem I : Effect on the generation of P700 ·+ A1 ·- radical pairs as studied by W-band transient EPR. In: Applied Magnetic Resonance. 2010 ; Vol. 37, No. 1. pp. 85-102.
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abstract = "Photosystem I (PS I) mutants from the cyanobacterium Synechocystis sp. PCC 6803 bearing point mutations to the axial ligands of A0A (M688NPsaA) and A0B (M668NPsaB) were studied by high-field W-band electron paramagnetic resonance (EPR) spectroscopy. It was found that the EPR observables of PS I from the M668NPsaB mutant were virtual identical to that of the wild type (WT), and are clearly distinct from the M688NPsaA mutant. In particular, the P700 ·+ decay kinetics in the M688NPsaA mutant is significantly slower than in the WT or the M668NPsaB mutant. The analysis of the out-of-phase electron-electron dipolar electron spin echo envelope modulation shows that in the M668NPsaB mutant, the estimated distance of 26.0 ± 0.3 {\AA} agrees well with the 25.8 {\AA} distance for the P700 ·+A1A ·- radical pair measured in the X-ray crystal structure. In the M688NPsaA mutant, two populations are found with estimated distances of 26.0 ± 0.3 and 25.0 ± 0.3 {\AA} in a ratio of 0.7-0.3, which agree well with the 25.8 {\AA} distance for the P700 ·+A1A ·- radical pair and the 24.6 {\AA} distance for the P700 ·+A1B ·- radical pair measured in the X-ray crystal structure. The data confirm that under the experimental conditions employed in this work, which involve dark-adapted samples without the pre-reduction of the iron-sulfur clusters, electron transport in cyanobacterial PS I is asymmetrical at 100 K, with the majority of electron transfer taking place through the A-branch of cofactors.",
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T1 - Alteration of the axial met ligand to electron acceptor A0 in photosystem I

T2 - Effect on the generation of P700 ·+ A1 ·- radical pairs as studied by W-band transient EPR

AU - Savitsky, Anton

AU - Gopta, Oksana

AU - Mamedov, Mahir

AU - Golbeck, John H.

AU - Tikhonov, Alexander

AU - Möbius, Klaus

AU - Semenov, Alexey

PY - 2010

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AB - Photosystem I (PS I) mutants from the cyanobacterium Synechocystis sp. PCC 6803 bearing point mutations to the axial ligands of A0A (M688NPsaA) and A0B (M668NPsaB) were studied by high-field W-band electron paramagnetic resonance (EPR) spectroscopy. It was found that the EPR observables of PS I from the M668NPsaB mutant were virtual identical to that of the wild type (WT), and are clearly distinct from the M688NPsaA mutant. In particular, the P700 ·+ decay kinetics in the M688NPsaA mutant is significantly slower than in the WT or the M668NPsaB mutant. The analysis of the out-of-phase electron-electron dipolar electron spin echo envelope modulation shows that in the M668NPsaB mutant, the estimated distance of 26.0 ± 0.3 Å agrees well with the 25.8 Å distance for the P700 ·+A1A ·- radical pair measured in the X-ray crystal structure. In the M688NPsaA mutant, two populations are found with estimated distances of 26.0 ± 0.3 and 25.0 ± 0.3 Å in a ratio of 0.7-0.3, which agree well with the 25.8 Å distance for the P700 ·+A1A ·- radical pair and the 24.6 Å distance for the P700 ·+A1B ·- radical pair measured in the X-ray crystal structure. The data confirm that under the experimental conditions employed in this work, which involve dark-adapted samples without the pre-reduction of the iron-sulfur clusters, electron transport in cyanobacterial PS I is asymmetrical at 100 K, with the majority of electron transfer taking place through the A-branch of cofactors.

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