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The Role of Ubiquinone-10 in Cyclic Electron Transport in Rhodopsendomonas capsulata Ala pho+: Effects of Lyophilization and Extraction

Authors
  • Bowyer, John R.
  • Baccarini-Melandri, Assunta
  • Melandri, B. Andrea
  • Crofts, Antony R.
Type
Published Article
Journal
Zeitschrift für Naturforschung C
Publisher
Walter de Gruyter GmbH
Publication Date
Oct 01, 1978
Volume
33
Issue
9-10
Pages
704–711
Identifiers
DOI: 10.1515/znc-1978-9-1017
Source
De Gruyter
Keywords
License
Green

Abstract

1. The effects of lyophilization and the extraction of ubiquinone-10 on the kinetics of electron transport in Rhodopseudomonas capsulata Ala pho+ have been investigated. 2. Lyophilization reduced the amount of ferrocytochrome c2 photo-oxidized on a microsecond time scale following a single excitation. 3. Lyophilization increased the reactivity of the electron transfer components with redox mediators, particularly N-methyl phenazonium methosulphate (PMS). At a concentration of 1 µᴍ , PMS accelerated reaction center re-reduction, ferricytochrome c2 re-reduction and ferrocytochrome b50 oxidation. The cytochrome c2 re-reduction stimulated by PMS was antimycin A insensitive but the cytochrome b50 oxidation was partially antim ycin sensitive. 4. Removal of 25- 30 molecules of ubiquinone 10 per reaction center removed a secondary acceptor pool, had very little effect on the kinetics of ferricytochrome b50 reduction and ferricyto­ chrome c2 re-reduction, but markedly inhibited ferrocytochrome b50 oxidation. Ubiquinone extraction also caused an increased stimulation of ferrocytochrome b50 oxidation by PMS. 5. The involvement of tightly bound ubiquinone in cytochrome b reduction and in the cytochrome b-c2 oxido-reductase, and the role of semiquinone species is discussed.

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