The complete amino acid sequence of a constitutive form of liver microsomal cytochrome P-450

• Published in: The Journal of biological chemistry Vol. 260; no. 9; pp. 5427 - 5434
• Main Authors: Ozols, J, Heinemann, F S, Johnson, E F
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Elsevier Inc 10.05.1985; American Society for Biochemistry and Molecular Biology
• Subjects: Amino Acid Sequence; Analytical, structural and metabolic biochemistry; Animals; Biological and medical sciences; Chromatography, High Pressure Liquid; Cytochrome P-450 Enzyme System - analysis; Fundamental and applied biological sciences. Psychology; Hemoproteins; Isoenzymes - analysis; Metalloproteins; Microsomes, Liver - enzymology; Models, Molecular; Molecular Weight; Proteins; Rabbits; Primary structure; Hemoprotein; Molecular structure; Microsome; Cytochrome P450; Liver
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(18)89040-8

The complete covalent structure of the constitutive cytochrome P-450, form 3b, from rabbit liver microsomes was determined. The apocytochrome contains 490 amino acid residues in a single polypeptide chain, Mr = 55,860. Peptides from selective chemical and proteolytic cleavages were isolated by a combination of gel filtration and high performance liquid chromatography and sequenced by automated Edman degradation. Overlapping peptide sequences were used to deduce the complete sequence. The constitutive form is only 46% homologous to the phenobarbital-induced cytochrome P-450 (Heinemann, F. S., and Ozols, J. (1983) J. Biol. Chem. 258, 4195-4201) and contains a deletion at position 22. Strongly conserved regions include Cys435 and a previously identified tryptic peptide, residues 345-357. The distribution of hydrophobic segments is used to predict the membrane topology of the protein, and four possible orientations of this protein in the membrane are presented.