Immunochemical studies on electron transport chains involving cytochrome P-450. The role of the iron-sulfur protein, adrenodoxin, in mixed-function oxidation reactions

Jeffrey Baron, Wayne E. Taylor, Bettie Sue Siler Masters

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Abstract

An antibody prepared to the homogeneous iron-sulfur protein (adrenodoxin) isolated from bovine adrenocortical mitochondria has been used to evaluate the role of adrenodoxin in cyt. P-450-mediated reactions in adrenal cortex and liver. As evidenced by the diminished magnitude of the g = 1.94 signal in electron paramagnetic resonance spectra of mitochondrial preparations at 100 °K, this antibody decreases the amount of adrenodoxin which can be reduced by either TPNH or sodium dithionite. The interaction between the antibody and adrenodoxin in mitochondrial preparations results in the concomitant inhibition of TPNH-cyt. c reductase and TPNH-cyt. P-450 reductase activities, as well as inhibition of the 11β-hydroxylation of 11-deoxycorticosterone. Inhibition by this antibody of TPNH-cyt. c reductase activity in a soluble fraction (fraction S2) prepared from sonicated adrenocortical mitochondria was reversed by the addition of homogeneous adrenodoxin, demonstrating that the antibody is specific for adrenodoxin. The antibody did not inhibit DPNH-cyt. c reductase activity or the reduction of the dye, dichlorophenolindophenol, by either TPNH or DPNH in fraction S2 of adrenocortical mitochondria. The antibody to adrenodoxin did not inhibit the TPNH-dependent reductions of either cyt. c or cyt. P-450 using microsomes prepared from bovine adrenal cortex or from the livers of untreated, phenobarbital-treated, or 3-methylcholanthrene-treated rats. No inhibition by this antibody was observed in substrate hydroxylations by these microsomal preparations. These observations indicate that adrenodoxin or an immunochemically similar iron-sulfur protein is not involved in cyt. P-450-mediated reactions in the microsomal fraction of liver or adrenal cortex.

Original languageEnglish (US)
Pages (from-to)105-115
Number of pages11
JournalArchives of Biochemistry and Biophysics
Volume150
Issue number1
DOIs
StatePublished - May 1972

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ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology

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