Complete amino acid sequence and predicted membrane topology of phenobarbital-induced cytochrome P-450 (isozyme 2) from rabbit liver microsomes.
The complete amino acid sequence of phenobarbital-induced isozyme 2 of rabbit liver microsomal cytochrome P-450 (P-450LM2) is presented. The polypeptide consists of 491 residues with a calculated Mr of 55,755. The rabbit isozyme is 77% identical to the corresponding rat cytochrome, P-450b, as deduced from cDNA, with 96% of the hydrophobic, 88% of the anionic, and 83% of the cationic positions conserved. The secondary structure of isozyme 2 was predicted and a model was developed for the membrane topology of this cytochrome. Of the two highly conserved cysteinyl peptides in P-450LM2, P-450b, and bacterial P-450cam, we favor, on the basis of our model, the one nearer the NH2 terminus (Cys-152 in P-450LM2) as the source of the thiolate ligand to the heme iron atom. The recently reported sequence of the apparently identical protein [Heinemann, F. S. & Ozols, J. (1983) J. Biol. Chem. 258, 4195-4201] has two fewer residues and differs in 14 other amino acid assignments.
D000595:Amino Acid Sequence; D000818:Animals; D003577:Cytochrome P-450 Enzyme System; D006418:Heme; D007527:Isoenzymes; D008565:Membrane Proteins; D008862:Microsomes, Liver / Q000201:enzymology / Q000648:ultrastructure*; D011487:Protein Conformation; D011817:Rabbits
D007527:Isoenzymes; D008565:Membrane Proteins; D006418:Heme; D003577:Cytochrome P-450 Enzyme System