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 journalArticlepeer-review

40 Scopus citations

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

Keywords

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

ASJC Scopus subject areas

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

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