Processing-independent in vitro translocation of cytochrome P-450(SCC) precursor across mitochondrial membranes.

In the presence of a membrane-permeable metal chelator, bovine adrenal cortex mitochondria imported P-450(SCC) precursor without processing of the amino-terminal extension peptide. The imported precursor was bound to the matrix side surface of the inner membrane. When the inhibition due to the metal chelator was removed, the imported precursor was processed to the mature form.

Structural analysis of cloned cDNA for mRNA of microsomal cytochrome P-450(C21) which catalyzes steroid 21-hydroxylation in bovine adrenal cortex.

We have isolated cDNA clones of the mRNA for cytochrome P-450 that catalyzes the steroid C-21 hydroxylation (P-450(C21)), which specifically catalyzes 21-hydroxylation of steroids in the microsomes of bovine adrenal cortex by using synthetic oligonucleotides as probes. Sequence determination of the cloned cDNA showed that it contains 2157 nucleotides and a poly(A) chain and that a single open reading frame of 1488 nucleotides codes for a polypeptide of 496 amino acids with a molecular weight of 56,113. The deduced amino acid composition is in agreement with that determined by direct amino acid analysis of purified P-450(C21) and the predicted primary structure contained amino acid sequences of N-terminal region and two internal tryptic fragments of the protein so far analyzed.

Possible steroid binding site common to adrenal cytochrome P-450scc and prostatic steroid binding protein.

By searching the entire PIR-protein-sequence data base, we have found that a dodecapeptide sequence in bovine adrenal cytochrome P-450scc is closely related to that in rat prostatic steroid binding protein. The two proteins belong to unrelated protein families, but both have steroids as substrates or ligands. Thus, the dodecapeptides may be important for substrate/ligand recognition in the individual proteins.

Molecular cloning and nucleotide sequence of cDNA for mRNA of mitochondrial cytochrome P-450(SCC) of bovine adrenal cortex.

We have isolated cDNA clones of the mRNA for cytochrome P-450(SCC), which catalyzes the side-chain cleavage reaction of cholesterol in bovine adrenal cortex mitochondria, by using synthetic oligonucleotides as probes. Sequence analysis of the cloned cDNAs enabled us to deduce the primary structure of the precursor form of P-450(SCC), which consisted of 520 amino acids and contained an extrapeptide of 39 amino acids at the NH2 terminus. The amino acid sequence from the 40th to 55th amino acid residue in the predicted structure completely coincided with the sequence of the NH2-terminal portion of purified P-450(SCC).

Induction of mRNA coding for phenobarbital-inducible form of microsomal cytochrome P-450 in rat liver by administration of 1,1-Di(p-chlorophenyl)-2,2-dichloroethylene and phenobarbital.

In the preceding paper (Yoshioka, H., et al. (1984) J.

Position specificity in n-hexane hydroxylation by two forms of cytochrome P-450 in rat liver microsomes.

The hydroxylation of n-hexane by rat liver microsomes was studied and the contribution of different molecular species of cytochrome P-450 to the hydroxylation reaction was examined. In the case of untreated rats, the products of NADPH-dependent n-hexane hydroxylation were 1-, 2-, and 3-hexanols, and the major one was 2-hexanol. Phenobarbital (PB) treatment of animals resulted in a significant increase of the hydroxylation activity.