Linked Life Data

11607279

Source:http://linkedlifedata.com/resource/pubmed/id/11607279

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
4
pubmed:dateCreated
2001-10-18
pubmed:abstractText
Photoinhibition of photosynthesis was studied in isolated photosystem II membranes by using chlorophyll fluorescence and electron paramagnetic resonance (EPR) spectroscopy combined with protein analysis. Under anaerobic conditions four sequentially intermediate steps in the photoinhibitory process were identified and characterized. These intermediates show high dark chlorophyll fluorescence (Foi) with typical decay kinetics (fast, semistable, stable, and nondecaying). The fast-decaying state has no bound QB but possesses a single reduced QA species with a 30-s decay half-time in the dark (QB, second quinone acceptor; QA, first quinone acceptor). In the semistable state, Q-A is stabilized for 2-3 min, most likely by protonation, and gives rise to the Q-A Fe2+ EPR signal in the dark. In the stable state, QA has become double reduced and is stabilized for 0.5-2 hr by protonation and a protein conformational change. The final, nondecaying state is likely to represent centers where QA H2 has left its binding site. The first three photoinhibitory states are reversible in the dark through reestablishment of QA to QB electron transfer. Significantly, illumination at 4 K of anaerobically photoinhibited centers trapped in all but the fast state gives rise to a spinpolarized triplet EPR signal from chlorophyll P680 (primary electron donor). When oxygen is introduced during anaerobic illumination, the light-inducible chlorophyll triplet is lost concomitant with induction of D1 protein degradation. The results are integrated into a model for the photoinhibitory process involving initial loss of bound QB followed by stable reduction and subsequent loss of QA facilitating chlorophyll P680 triplet formation. This in turn mediates light-induced formation of highly reactive and damaging singlet oxygen.
pubmed:commentsCorrections
pubmed:language
eng
pubmed:journal
pubmed:status
PubMed-not-MEDLINE
pubmed:month
Feb
pubmed:issn
0027-8424
pubmed:author
pubmed:issnType
Print
pubmed:day
15
pubmed:volume
89
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
1408-12
pubmed:dateRevised
2010-9-14
pubmed:year
1992
pubmed:articleTitle
Reversible and irreversible intermediates during photoinhibition of photosystem II: stable reduced QA species promote chlorophyll triplet formation.
pubmed:affiliation
Department of Biochemistry, Stockholm University, Stockholm, Sweden.
pubmed:publicationType
Journal Article