Direct interaction between mitochondrial succinate-ubiquinone and ubiquinol-cytochrome c oxidoreductases probed by sensitivity to quinone-related inhibitors

Atsuko Yamashita, Hideto Miyoshi, Taku Hatano, Hajime Iwamura

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

The electron-transfer activities of bovine heart mitochondrial complexes I, II, and III, but not complex IV, were simultaneously inhibited by 2-alkyl-4,6-dinitrophenols to a different extent. The extent of inhibition of NADH and succinate oxidase activities by dinitrophenols was compared with that of individual complex activities using submitochondrial particles. The extent of inhibition of succinate oxidase activity by 1-methylpropyl and 1-methylbutyl derivatives was much larger than that of NADH oxidase activity. This large inhibition of succinate oxidase activity seemed not to be explainable by the extent of inhibition of individual complex activities (i.e., complexes II and III activities), based upon the homogeneous ubiquinone pool model. On the other hand, other dinitrophenols (n-propyl, 1-methylpentyl, 1-methylhexyl, and tert-butyl derivatives) very similar to the above compounds did not elicit such anomalous inhibitory action, indicating that the action of 1-methylpropyl and 1-methylbutyl derivatives is highly specific to their structure. The anomalous inhibition by these two compounds was also observed with the isolated succinate-cytochrome c oxidoreductase, in which there is no ubiquinone pool behavior. However, when the succinate-cytochrome c reductase of which the activity had been partially restored by adding phospholipid and exogenous quinone to the phospholipid- and ubiquinone-depleted succinate-cytochrome c reductase was assayed, the anomalous inhibitory action of interest was undetectable. These results indicated that electron-transfer between complexes II and III, which is mediated not only by free-form, but also by protein-bound ubiquinone, occurs in the mitochondrial membrane. The fact that the anomalous inhibition of succinate oxidase activity of submitochondrial particles was sensitive to changes in the external osmotic pressure which affected the total area of the particle supports this notion.

Original languageEnglish
Pages (from-to)377-384
Number of pages8
JournalJournal of biochemistry
Volume120
Issue number2
DOIs
Publication statusPublished - Jan 1 1996
Externally publishedYes

Keywords

  • Electron-transfer inhibitor
  • Mitochondrial electron-transfer
  • Succinate-ubiquinone oxidoreductase
  • Ubiquinol-cytochrome c oxidoreductase
  • Ubiquinone-pool

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology

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