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

Willem Vermaas, Gaozhong Shen, Stenbjörn Styling

Research output: Contribution to journalArticle

39 Citations (Scopus)

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

Fingerprint

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

Keywords

  • Electron transport
  • KCN-sensitive oxidase
  • Photosynthesis
  • Plastoquinone
  • Respiration
  • Thylakoid membrane

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Molecular Biology

Cite this

Electrons generated by photosystem II are utilized by an oxidase in the absence of photosystem I in the cyanobacterium Synechocystis sp. PCC 6803. / Vermaas, Willem; 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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N2 - 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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