Advanced

Light adaptation of Photosystem II is mediated by the plastoquinone pool.

Åhrling, Karin A and Peterson Årsköld, Sindra LU (2003) In Biochemistry 42(25). p.7655-7662
Abstract
During the first few enzymatic turnovers after dark adaptation of photosystem II (PSII), the relaxation rate of the EPR signals from the Mn cluster and YD(dot) are significantly enhanced. This light-adaptation process has been suggested to involve the appearance of a new paramagnet on the PSII donor side [Peterson, Åhrling, Hogblom, and Styring, Biochemistry 2003, asap]. In the present study, a correlation is established between the observed relaxation enhancement and the redox state of the quinone pool. It is shown that the addition of quinol to dark-adapted PSII membrane fragments induces relaxation enhancement already after a single oxidation of the Mn, comparable to that observed after five oxidations in samples with quinones (PPBQ or... (More)
During the first few enzymatic turnovers after dark adaptation of photosystem II (PSII), the relaxation rate of the EPR signals from the Mn cluster and YD(dot) are significantly enhanced. This light-adaptation process has been suggested to involve the appearance of a new paramagnet on the PSII donor side [Peterson, Åhrling, Hogblom, and Styring, Biochemistry 2003, asap]. In the present study, a correlation is established between the observed relaxation enhancement and the redox state of the quinone pool. It is shown that the addition of quinol to dark-adapted PSII membrane fragments induces relaxation enhancement already after a single oxidation of the Mn, comparable to that observed after five oxidations in samples with quinones (PPBQ or DQ) added. The saturation behavior of YD(dot) revealed that with quinol added in the dark, a single flash was necessary for the relaxation enhancement to occur. The quinol-induced relaxation enhancement of PSII was also activated by illumination at 200 K. Whole thylakoids, with no artificial electron acceptor present but with an intact plastoquinone pool, displayed the same relaxation enhancement on the fifth flash as membrane fragments with exogenous quinones present. We conclude that (i) reduction of the quinone pool induces the relaxation enhancement of the PSII donor-side paramagnets, (ii) light is required for the quinol to effect the relaxation enhancement, and (iii) light-adaptation occurs in the intact thylakoid system, when the endogenous plastoquinone pool is gradually reduced by PSII turnover. It seems clear that a species on the PSII donor side is reduced by the quinol, to become a potent paramagnetic relaxer. On the basis of XANES reports, we suggest that this species may be the Mn ions not involved in the cyclic redox changes of the oxygen-evolving complex. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
MN CLUSTER, MANGANESE CLUSTER, EPR MULTILINE SIGNAL, MICROWAVE-POWER SATURATION, PHOTOSYNTHETIC WATER OXIDATION, OXYGEN-EVOLVING COMPLEX, ELECTRON-PARAMAGNETIC-RESONANCE, CRYSTAL-STRUCTURE, ACCEPTOR COMPLEX, S-0 STATE
in
Biochemistry
volume
42
issue
25
pages
7655 - 7662
publisher
The American Chemical Society
external identifiers
  • Scopus:0038001460
ISSN
0006-2960
DOI
10.1021/bi034349l
language
English
LU publication?
yes
id
a008cbfc-38fe-4cee-a790-ac6d5333486e (old id 120930)
date added to LUP
2007-07-06 17:02:06
date last changed
2016-10-13 04:38:11
@misc{a008cbfc-38fe-4cee-a790-ac6d5333486e,
  abstract     = {During the first few enzymatic turnovers after dark adaptation of photosystem II (PSII), the relaxation rate of the EPR signals from the Mn cluster and YD(dot) are significantly enhanced. This light-adaptation process has been suggested to involve the appearance of a new paramagnet on the PSII donor side [Peterson, Åhrling, Hogblom, and Styring, Biochemistry 2003, asap]. In the present study, a correlation is established between the observed relaxation enhancement and the redox state of the quinone pool. It is shown that the addition of quinol to dark-adapted PSII membrane fragments induces relaxation enhancement already after a single oxidation of the Mn, comparable to that observed after five oxidations in samples with quinones (PPBQ or DQ) added. The saturation behavior of YD(dot) revealed that with quinol added in the dark, a single flash was necessary for the relaxation enhancement to occur. The quinol-induced relaxation enhancement of PSII was also activated by illumination at 200 K. Whole thylakoids, with no artificial electron acceptor present but with an intact plastoquinone pool, displayed the same relaxation enhancement on the fifth flash as membrane fragments with exogenous quinones present. We conclude that (i) reduction of the quinone pool induces the relaxation enhancement of the PSII donor-side paramagnets, (ii) light is required for the quinol to effect the relaxation enhancement, and (iii) light-adaptation occurs in the intact thylakoid system, when the endogenous plastoquinone pool is gradually reduced by PSII turnover. It seems clear that a species on the PSII donor side is reduced by the quinol, to become a potent paramagnetic relaxer. On the basis of XANES reports, we suggest that this species may be the Mn ions not involved in the cyclic redox changes of the oxygen-evolving complex.},
  author       = {Åhrling, Karin A and Peterson Årsköld, Sindra},
  issn         = {0006-2960},
  keyword      = {MN CLUSTER,MANGANESE CLUSTER,EPR MULTILINE SIGNAL,MICROWAVE-POWER SATURATION,PHOTOSYNTHETIC WATER OXIDATION,OXYGEN-EVOLVING COMPLEX,ELECTRON-PARAMAGNETIC-RESONANCE,CRYSTAL-STRUCTURE,ACCEPTOR COMPLEX,S-0 STATE},
  language     = {eng},
  number       = {25},
  pages        = {7655--7662},
  publisher    = {ARRAY(0xb3cd488)},
  series       = {Biochemistry},
  title        = {Light adaptation of Photosystem II is mediated by the plastoquinone pool.},
  url          = {http://dx.doi.org/10.1021/bi034349l},
  volume       = {42},
  year         = {2003},
}