Characterization of three forms of rabbit microsomal cytochrome P-450 by peptide mapping utilizing limited proteolysis in sodium dodecyl sulfate and analysis by gel electrophoresis.

Limited proteolysis of three forms of rabbit liver microsomal cytochrome P-450 by Staphylococcus aureus V₈ protease, α-chymotrypsin, or papain in the presence of sodium dodecyl sulfate produces peptide fragments having a unique molecular weight distribution for each cytochrome. These differences are observed for the major cytochrome P-450 induced by phenobarbital and two forms induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin. Our results indicate that the primary structures of these three cytochromes are substantially different. In addition, the characteristic pattern of peptide fragments produced from each cytochrome facilitates the identification of the cytochromes in microsomal preparations when peptide mapping is utilized in conjunction with polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Using this methodology, the occurrence and induction of the cytochromes in tissue preparations can be monitored.