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The role of cytochrome b559 and tyrosineD in protection against photoinhibition during in vivo photoactivation of Photosystem II

Magnusson, Ann; Rova, Maria; Mamedov, Fikret LU ; Fredriksson, Per-Olof and Styring, Stenbjörn LU (1999) In Biochimica et Biophysica Acta - Bioenergetics 1411(1). p.180-191
Abstract
In vivo photoactivation of Photosystem II was studied in the FUD39 mutant strain of the green alga Chlamydomonas reinhardtii which lacks the 23 kDa protein subunit involved in water oxidation. Dark grown cells, devoid of oxygen evolution, were illuminated at 0.8 μE m-2&#;s-1 light intensity which promotes optimal activation of oxygen evolution, or at 17 μE m-2&#;s-1, where photoactivation compete with deleterious photodamage. The involvement of the two redox active cofactors tyrosineD and cytochrome b559 during the photoactivation process, was investigated by EPR spectroscopy. TyrosineD on the D2 reaction center protein functions as auxiliary electron donor to the primary donor P680+ during the first minutes of photoactivation at... (More)
In vivo photoactivation of Photosystem II was studied in the FUD39 mutant strain of the green alga Chlamydomonas reinhardtii which lacks the 23 kDa protein subunit involved in water oxidation. Dark grown cells, devoid of oxygen evolution, were illuminated at 0.8 μE m-2&#;s-1 light intensity which promotes optimal activation of oxygen evolution, or at 17 μE m-2&#;s-1, where photoactivation compete with deleterious photodamage. The involvement of the two redox active cofactors tyrosineD and cytochrome b559 during the photoactivation process, was investigated by EPR spectroscopy. TyrosineD on the D2 reaction center protein functions as auxiliary electron donor to the primary donor P680+ during the first minutes of photoactivation at 0.8 μE m-2&#;s-1 (compare with Rova et al., Biochemistry, 37 (1998) 11039-11045.). Here we show that also cytochrome b559 was rapidly oxidized during the first 10 min of photoactivation with a similar rate to tyrosineD. This implies that both cytochrome b559 and tyrosineD may function as auxiliary electron donors to P680+ and/or the oxidized tyrosine&#;Z on the D1 protein, to avoid photoinhibition before successful photoactivation was accomplished. As the catalytic water-oxidation successively became activated, TyrosineD remained oxidized while cytochrome b559 became rereduced to the equilibrium level that was observed prior to photoactivation. At 17 μE m-2&#;s-1 light intensity, where photoinhibition competes significantly with photoactivation, tyrosineD was very rapidly completely oxidized, after which the amount of oxidized tyrosineD decreased due to photoinhibition. In contrast, cytochrome b559 became reduced during the first 2 min of photoactivation at 17 μE m-2&#;s-1. After this, it was reoxidized, returning to the equilibrium level within 10 min. Thus, during in vivo photoactivation in high-light cytochrome b559 serves two functions. Initially, it probably oxidizes the reduced primary acceptor pheophytin, thereby relieving the acceptor side of reductive pressure, and later on it serves as auxiliary electron donor, preventing donor-side photoinhibition. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Biochimica et Biophysica Acta - Bioenergetics
volume
1411
issue
1
pages
180 - 191
publisher
Elsevier
external identifiers
  • scopus:0032910596
ISSN
0005-2728
DOI
10.1016/S0005-2728(99)00044-4
language
English
LU publication?
yes
id
05cd73e4-4947-4f92-81f3-0d8ae9fa2fa2 (old id 125358)
date added to LUP
2007-07-06 10:54:32
date last changed
2017-07-30 04:45:53
@article{05cd73e4-4947-4f92-81f3-0d8ae9fa2fa2,
  abstract     = {In vivo photoactivation of Photosystem II was studied in the FUD39 mutant strain of the green alga Chlamydomonas reinhardtii which lacks the 23 kDa protein subunit involved in water oxidation. Dark grown cells, devoid of oxygen evolution, were illuminated at 0.8 μE m-2&#;s-1 light intensity which promotes optimal activation of oxygen evolution, or at 17 μE m-2&#;s-1, where photoactivation compete with deleterious photodamage. The involvement of the two redox active cofactors tyrosineD and cytochrome b559 during the photoactivation process, was investigated by EPR spectroscopy. TyrosineD on the D2 reaction center protein functions as auxiliary electron donor to the primary donor P680+ during the first minutes of photoactivation at 0.8 μE m-2&#;s-1 (compare with Rova et al., Biochemistry, 37 (1998) 11039-11045.). Here we show that also cytochrome b559 was rapidly oxidized during the first 10 min of photoactivation with a similar rate to tyrosineD. This implies that both cytochrome b559 and tyrosineD may function as auxiliary electron donors to P680+ and/or the oxidized tyrosine&#;Z on the D1 protein, to avoid photoinhibition before successful photoactivation was accomplished. As the catalytic water-oxidation successively became activated, TyrosineD remained oxidized while cytochrome b559 became rereduced to the equilibrium level that was observed prior to photoactivation. At 17 μE m-2&#;s-1 light intensity, where photoinhibition competes significantly with photoactivation, tyrosineD was very rapidly completely oxidized, after which the amount of oxidized tyrosineD decreased due to photoinhibition. In contrast, cytochrome b559 became reduced during the first 2 min of photoactivation at 17 μE m-2&#;s-1. After this, it was reoxidized, returning to the equilibrium level within 10 min. Thus, during in vivo photoactivation in high-light cytochrome b559 serves two functions. Initially, it probably oxidizes the reduced primary acceptor pheophytin, thereby relieving the acceptor side of reductive pressure, and later on it serves as auxiliary electron donor, preventing donor-side photoinhibition.},
  author       = {Magnusson, Ann and Rova, Maria and Mamedov, Fikret and Fredriksson, Per-Olof and Styring, Stenbjörn},
  issn         = {0005-2728},
  language     = {eng},
  number       = {1},
  pages        = {180--191},
  publisher    = {Elsevier},
  series       = {Biochimica et Biophysica Acta - Bioenergetics},
  title        = {The role of cytochrome b559 and tyrosineD in protection against photoinhibition during in vivo photoactivation of Photosystem II},
  url          = {http://dx.doi.org/10.1016/S0005-2728(99)00044-4},
  volume       = {1411},
  year         = {1999},
}