Purification and structural comparison of pulmonary and hepatic cytochrome P-450 from rabbits

A procedure is described for the purification of a major form of cytochrome P-450 from the livrs of rabbits treated with phenobarbital and a major form of the cytochrome from the lungs of untreated rabbits. Preparations in good yield (13--17%) and of high purity (up to 21 nmol of cytochrome per mg of protein) that were free of lipid and contained minimal amounts of non-ionic detergent were obtained from either tissue. The two cytochromes cannot be distinguished from each other on the basis of absorption spectra, extinction coefficients, apparent molecular weights (52 000), amino acid compositions, or peptide fragments produced by treatment of the proteins with cyanogen bromide. These data are consistent with a major indigenous form of rabbit pulmonary cytochrome P-450 being the same as the major form of hepatic cytochrome induced by phenobarbital.