Electron flow between photosystem II and oxygen in chloroplasts of photosystem I-deficient algae is mediated by a quinol oxidase involved in chlororespiration

L Cournac, K Redding, J Ravenel, D Rumeau, Eve-Marie Josse, M Kuntz, G Peltier

Research output: Contribution to journalArticlepeer-review

Abstract

In Chlamydomonas reinhardtii mutants deficient in photosystem I because of inactivation of the chloroplast genes psaA or psaB, oxygen evolution from photosystem II occurs at significant rates and is coupled to a stimulation of oxygen uptake. Both activities can be simultaneously monitored by continuous mass spectrometry in the presence of (18)O(2). The light-driven O(2) exchange was shown to involve the plastoquinone pool as an electron carrier, but not cytochrome b(6)f. Photosystem II-dependent O(2) production and O(2) uptake were observed in isolated chloroplast fractions. Photosystem II-dependent oxygen exchange was insensitive to a variety of inhibitors (azide, carbon monoxide, cyanide, antimycin A, and salicylhydroxamic acid) and radical scavengers. It was, however, sensitive to propyl gallate. From inhibitors effects and electronic requirements of the O(2) uptake process, we conclude that an oxidase catalyzing oxidation of plastoquinol and reduction of oxygen to water is present in thylakoid membranes. From the sensitivity of flash-induced O(2) exchange to propyl gallate, we conclude that this oxidase is involved in chlororespiration. Clues to the identity of the protein implied in this process are given by pharmacological and immunological similarities with a protein (IMMUTANS) identified in Arabidopsis chloroplasts.
Original languageEnglish
Pages (from-to)17256-62
Number of pages7
JournalJournal of Biological Chemistry
Volume275
Issue number23
DOIs
Publication statusPublished - 2000

Keywords

  • Animals
  • Antimycin A
  • Azides
  • Carbon Monoxide
  • Chlamydomonas reinhardtii
  • Chlorophyll
  • Chloroplasts
  • Electron Transport
  • Free Radical Scavengers
  • Kinetics
  • Light-Harvesting Protein Complexes
  • Oxidoreductases
  • Oxygen
  • Oxygen Consumption
  • Photosynthesis
  • Photosynthetic Reaction Center Complex Proteins
  • Photosystem I Protein Complex
  • Photosystem II Protein Complex
  • Salicylamides

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