Electrons generated by photosystem II are utilized by an oxidase in the absence of photosystem I in the cyanobacterium Synechocystis sp. PCC 6803

Wim F.J. Vermaas, Gaozhong Shen, Stenbjörn Styling

Research output: Contribution to journalArticle

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Abstract

The reduction and reoxidation kinetics of the first quinone-type electron acceptor in photosystem II, QA-, were measured by fluorescence in a light-tolerant, photosystem I-less strain of the cyanobacterium Synechocystis sp. PCC 6803. In this strain, which shows excellent amplitudes of variable fluorescence, the rate of QA- oxidation after photoreduction of the plastoquinone pool was about half of that in the presence of photosystem I. However, upon addition of 5 mM KCN, QA- decay was very slow, and the rate was comparable to that seen in the presence of diuron, which blocks electron transport between QA and QB. The KCN-imposed block of QA- oxidation was removed efficiently by addition of exogenous quinones that can oxidize the plastoquinone pool. These results indicate that, in the absence of photosystem I, photosystem II-generated electrons are used very effectively by an oxidase located in the thylakoid; this oxidase may be a component of the respiratory chain.

Original languageEnglish (US)
Pages (from-to)103-108
Number of pages6
JournalFEBS Letters
Volume337
Issue number1
DOIs
StatePublished - Jan 3 1994

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Synechocystis
Photosystem I Protein Complex
Photosystem II Protein Complex
Cyanobacteria
Plastoquinone
Oxidoreductases
Electrons
Electron Transport
Fluorescence
Diuron
Quinones
Oxidation
Thylakoids
Light
Kinetics

All Science Journal Classification (ASJC) codes

  • Biophysics
  • Structural Biology
  • Biochemistry
  • Molecular Biology
  • Genetics
  • Cell Biology

Cite this

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title = "Electrons generated by photosystem II are utilized by an oxidase in the absence of photosystem I in the cyanobacterium Synechocystis sp. PCC 6803",
abstract = "The reduction and reoxidation kinetics of the first quinone-type electron acceptor in photosystem II, QA-, were measured by fluorescence in a light-tolerant, photosystem I-less strain of the cyanobacterium Synechocystis sp. PCC 6803. In this strain, which shows excellent amplitudes of variable fluorescence, the rate of QA- oxidation after photoreduction of the plastoquinone pool was about half of that in the presence of photosystem I. However, upon addition of 5 mM KCN, QA- decay was very slow, and the rate was comparable to that seen in the presence of diuron, which blocks electron transport between QA and QB. The KCN-imposed block of QA- oxidation was removed efficiently by addition of exogenous quinones that can oxidize the plastoquinone pool. These results indicate that, in the absence of photosystem I, photosystem II-generated electrons are used very effectively by an oxidase located in the thylakoid; this oxidase may be a component of the respiratory chain.",
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Electrons generated by photosystem II are utilized by an oxidase in the absence of photosystem I in the cyanobacterium Synechocystis sp. PCC 6803. / Vermaas, Wim F.J.; Shen, Gaozhong; Styling, Stenbjörn.

In: FEBS Letters, Vol. 337, No. 1, 03.01.1994, p. 103-108.

Research output: Contribution to journalArticle

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AB - The reduction and reoxidation kinetics of the first quinone-type electron acceptor in photosystem II, QA-, were measured by fluorescence in a light-tolerant, photosystem I-less strain of the cyanobacterium Synechocystis sp. PCC 6803. In this strain, which shows excellent amplitudes of variable fluorescence, the rate of QA- oxidation after photoreduction of the plastoquinone pool was about half of that in the presence of photosystem I. However, upon addition of 5 mM KCN, QA- decay was very slow, and the rate was comparable to that seen in the presence of diuron, which blocks electron transport between QA and QB. The KCN-imposed block of QA- oxidation was removed efficiently by addition of exogenous quinones that can oxidize the plastoquinone pool. These results indicate that, in the absence of photosystem I, photosystem II-generated electrons are used very effectively by an oxidase located in the thylakoid; this oxidase may be a component of the respiratory chain.

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