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Flash-induced relaxation changes of the EPR signals from the manganese cluster and YD reveal a light-adaptation process of Photosystem II

Peterson Årsköld, Sindra LU ; Åhrling, Karin A; Högblom, Joakim LU and Styring, Stenbjörn LU (2003) In Biochemistry 42(9). p.2748-2758
Abstract
By exposing photosystem II (PSII) samples to an incrementing number of excitation flashes at room temperature, followed by freezing, we could compare the Mn-derived multiline EPR signal from the S-2 oxidation state as prepared by 1, 5, 10, and 25 flashes of light. While the S-2 multiline signals exhibited by these samples differed very little in spectral shape, a significant increase of the relaxation rate of the signal was detected in the multiflash samples as compared to the S-2-state produced by a single oxidation. A similar relaxation rate increase was observed for the EPR signal from Y-D(.). The temperature dependence of the multiline spin-lattice relaxation rate is similar after 1 and 5 flashes. These data are discussed together with... (More)
By exposing photosystem II (PSII) samples to an incrementing number of excitation flashes at room temperature, followed by freezing, we could compare the Mn-derived multiline EPR signal from the S-2 oxidation state as prepared by 1, 5, 10, and 25 flashes of light. While the S-2 multiline signals exhibited by these samples differed very little in spectral shape, a significant increase of the relaxation rate of the signal was detected in the multiflash samples as compared to the S-2-state produced by a single oxidation. A similar relaxation rate increase was observed for the EPR signal from Y-D(.). The temperature dependence of the multiline spin-lattice relaxation rate is similar after 1 and 5 flashes. These data are discussed together with previously reported phenomena in terms of a light-adaptation process of PSII, which commences on the third flash after dark-adaptation and is completed after 10 flashes. At room temperature, the fast-relaxing, light-adapted state falls back to the slow-relaxing, dark-adapted state with t(1/2) = 80 s. We speculate that light-adaptation involves changes necessary for efficient continuous water splitting. This would parallel activation processes found in many other large redox enzymes, such as Cytochrome c oxidase and Ni-Fe hydrogenase. Several mechanisms of light-adaptation are discussed, and we find that the data may be accounted for by a change of the PSII protein matrix or by the light-induced appearance of a paramagnetic center on the PSII donor side. At this time, no EPR signal has been detected that correlates with the increase of the relaxation rates, and the nature of such a new paramagnet remains unclear. However, the relaxation enhancement data could be used, in conjunction with the known Mn-Y-D distance, to estimate the position of such an unknown relaxer. If positioned between Y-D and the Mn cluster, it would be located 7-8 Angstrom from the spin center of the S-2 multiline signal. (Less)
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organization
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Contribution to journal
publication status
published
subject
keywords
MULTILINE SIGNAL, SATURATION-RECOVERY EPR, SPIN-LATTICE RELAXATION, PHOTOSYNTHETIC O2 EVOLUTION, OXYGEN-EVOLVING COMPLEX, S-2 STATE, ELECTRON-PARAMAGNETIC-RESONANCE, IRON-SULFUR PROTEINS, DYSPROSIUM COMPLEXES, INDUCED ENHANCEMENTS
in
Biochemistry
volume
42
issue
9
pages
2748 - 2758
publisher
The American Chemical Society
external identifiers
  • wos:000181372200028
  • scopus:0346665917
ISSN
0006-2960
DOI
language
English
LU publication?
yes
id
ffd73077-4085-40b4-8890-22deb68a5752 (old id 120924)
date added to LUP
2007-07-06 14:00:39
date last changed
2018-05-29 12:13:18
@article{ffd73077-4085-40b4-8890-22deb68a5752,
  abstract     = {By exposing photosystem II (PSII) samples to an incrementing number of excitation flashes at room temperature, followed by freezing, we could compare the Mn-derived multiline EPR signal from the S-2 oxidation state as prepared by 1, 5, 10, and 25 flashes of light. While the S-2 multiline signals exhibited by these samples differed very little in spectral shape, a significant increase of the relaxation rate of the signal was detected in the multiflash samples as compared to the S-2-state produced by a single oxidation. A similar relaxation rate increase was observed for the EPR signal from Y-D(.). The temperature dependence of the multiline spin-lattice relaxation rate is similar after 1 and 5 flashes. These data are discussed together with previously reported phenomena in terms of a light-adaptation process of PSII, which commences on the third flash after dark-adaptation and is completed after 10 flashes. At room temperature, the fast-relaxing, light-adapted state falls back to the slow-relaxing, dark-adapted state with t(1/2) = 80 s. We speculate that light-adaptation involves changes necessary for efficient continuous water splitting. This would parallel activation processes found in many other large redox enzymes, such as Cytochrome c oxidase and Ni-Fe hydrogenase. Several mechanisms of light-adaptation are discussed, and we find that the data may be accounted for by a change of the PSII protein matrix or by the light-induced appearance of a paramagnetic center on the PSII donor side. At this time, no EPR signal has been detected that correlates with the increase of the relaxation rates, and the nature of such a new paramagnet remains unclear. However, the relaxation enhancement data could be used, in conjunction with the known Mn-Y-D distance, to estimate the position of such an unknown relaxer. If positioned between Y-D and the Mn cluster, it would be located 7-8 Angstrom from the spin center of the S-2 multiline signal.},
  author       = {Peterson Årsköld, Sindra and Åhrling, Karin A and Högblom, Joakim and Styring, Stenbjörn},
  issn         = {0006-2960},
  keyword      = {MULTILINE SIGNAL,SATURATION-RECOVERY EPR,SPIN-LATTICE RELAXATION,PHOTOSYNTHETIC O2 EVOLUTION,OXYGEN-EVOLVING COMPLEX,S-2 STATE,ELECTRON-PARAMAGNETIC-RESONANCE,IRON-SULFUR PROTEINS,DYSPROSIUM COMPLEXES,INDUCED ENHANCEMENTS},
  language     = {eng},
  number       = {9},
  pages        = {2748--2758},
  publisher    = {The American Chemical Society},
  series       = {Biochemistry},
  title        = {Flash-induced relaxation changes of the EPR signals from the manganese cluster and YD reveal a light-adaptation process of Photosystem II},
  url          = {http://dx.doi.org/},
  volume       = {42},
  year         = {2003},
}