Studies on the succinate dehydrogenating system. Isolation and properties of the mitochondrial succinate-ubiquinone reductase

Biochim Biophys Acta. 1985 Sep 19;809(2):145-59. doi: 10.1016/0005-2728(85)90057-x.

Abstract

A simple procedure for preparation of highly purified soluble succinate-ubiquinone reductase from bovine heart mitochondrial particles is described. The enzyme exhibits four major bands on sodium dodecyl sulfate gel electrophoresis and contains (nmol per mg protein): covalently bound flavin, 6; non-heme iron, 53; acid-labile sulfur, 50; cytochrome b-560 heme, 1.2. The enzyme catalyzes thenoyltrifluoroacetone, or carboxin-sensitive (pure non-competitive with Q2) reduction of Q2 by succinate with a turnover number close to that in parent submitochondrial particles. The succinate reduced enzyme exhibits ferredoxin-type iron-sulfur center EPR-signal (g = 1.94 species) and a semiquinone signal (g = 2.00). An oxidized preparation shows a symmetric signal centered around g = 2.01. An unusual dissociation of the enzyme in the absence of a detergent is described. When added to the assay mixture from a concentrated protein-detergent solution, the enzyme does not reduce Q2 being highly reactive towards ferricyanide ('low Km ferricyanide reactive site'; Vinogradov, A.D., Gavrikova, E.V. and Goloveshkina, V.G. (1975) Biochem. Biophys. Res. Commun. 65, 1264-1269). The ubiquinone reductase, not the ferricyanide reductase was observed when the enzyme was added to the assay mixture from the diluted protein-detergent solutions. Thus the dissociation of succinate dehydrogenase from the complex occurs in the absence of a detergent dependent on the concentration of the protein-detergent complex in the stock preparation where the samples for the assay are taken from. An active antimycin-sensitive succinate-cytochrome c reductase was reconstituted by admixing of the soluble succinate-ubiquinone reductase and the cytochrome b-c1 complex, i.e., from the complexes which both contain the ubiquinone reactivity conferring protein (QPs). Cytochrome c reductase was also reconstituted from the succinate-ubiquinone reductase and succinate-cytochrome c reductase containing inactivated succinate dehydrogenase. The reconstitution experiments suggest that there exists a specific protein-protein (or lipid) interaction between QPs and a certain component(s) of the b-c1 complex.

MeSH terms

  • Animals
  • Binding Sites
  • Cattle
  • Electron Spin Resonance Spectroscopy
  • Electron Transport Complex II
  • Electrophoresis, Polyacrylamide Gel
  • Flavins / analysis
  • Heme / analysis
  • Iron / analysis
  • Kinetics
  • Mitochondria, Heart / enzymology*
  • Multienzyme Complexes / isolation & purification
  • Multienzyme Complexes / metabolism*
  • Octoxynol
  • Oxidation-Reduction
  • Oxidoreductases / isolation & purification
  • Oxidoreductases / metabolism*
  • Polyethylene Glycols / pharmacology
  • Spectrophotometry
  • Substrate Specificity
  • Succinate Dehydrogenase / isolation & purification
  • Succinate Dehydrogenase / metabolism*
  • Succinates / metabolism
  • Succinic Acid
  • Sulfur / analysis
  • Ubiquinone / analysis
  • Ubiquinone / metabolism

Substances

  • Flavins
  • Multienzyme Complexes
  • Succinates
  • Ubiquinone
  • Polyethylene Glycols
  • Heme
  • Sulfur
  • Octoxynol
  • Succinic Acid
  • Iron
  • Oxidoreductases
  • Electron Transport Complex II
  • Succinate Dehydrogenase
  • Ubiquinone Q2