Hepatic mitochondrial cytochrome P-450 system. Identification and characterization of a precursor form of mitochondrial cytochrome P-450 induced by 3-methylcholanthrene

B. G. Niranjan, H. Raza, R. M. Shayiq, C. R. Jefcoate, N. G. Avadhani

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21 Citations (Scopus)

Abstract

Hepatic mitoplasts from 3-methylcholanthrene-treated rats contain cytochrome P-450 which can metabolize polycyclic aromatic hydrocarbons like benz(a)pyrene. Mitochondrial cytochrome P-450 was partially purified and reconstituted in vitro using adrenodoxin and the adrenodoxin reductase electron transfer system and [3H]benzo(a)pyrene as the substrate. A polyclonal antibody to purified microsomal P-450c (a major 3-methylcholanthrene-inducible form) inhibited the activity of mitochondrial enzyme in a concentration-dependent manner and also reacted with a 54-kDa protein on the immunoblots. A monoclonal antibody having exclusive specficity for P-450c, on the other hand, did not inhibit the aryl hydrocarbon hydroxylase activity of the mitochondrial enzyme and showed no detectable cross-reaction with the 54-kDa mitochondrial protein. Similarly, two-dimensional analysis and immunodetection using the polyclonal antibody showed distinct molecular properties of the mitochondrial enzyme different from the similarly induced microsomal P-450c with respect to the isoelectric pH. In vitro translation of free polysomes from 3-methylcholanthrene-induced liver, transport of precursor proteins by isolated mitochondria in vitro, and immunoprecipitation with the polyclonal antibody showed the presence of a 57-kDa putative precursor which is transported and processed into mature 54-kDa species. These results present evidence for the true intramitochondrial location of the P-450c-antibody reactive isoform detected in 3-methylcholanthrene-induced rat liver mitochondria.

Original languageEnglish
Pages (from-to)575-580
Number of pages6
JournalJournal of Biological Chemistry
Volume263
Issue number1
Publication statusPublished - 1988
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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