Amino-terminal sequence of phenobarbital-inducible cytochrome P-450 from rabbit liver microsomes: Similarity to hydrophobic amino-terminal segments of preproteins

Abstract

Summary The amino-terminal sequence of two electrophoretically homogeneous forms of rabbit liver microsomal cytochrome P-450, P-450 LM 2 and P-45 LM 4 , has been examined by automated Edman degradation. Methionine is the amino terminus of P-450 LM 2 , and 17 of the first 20 residues are hydrophobic, including two clusters of five consecutive leucines. The composition and sequence of this region are similar to those of the short-lived hydrophobic amino-terminal precursor segments of certain other proteins, especially myeloma immunoglobulin light chains and pancreatic zymogens. Multiple amino-terminal residues, including methionine, were detected for P-450 LM 4 suggesting the presence of several highly similar forms of P-450 or that partial proteolysis had occurred.