Cleavage of newly translated NADPH-cytochrome P-450 reductase in a rabbit reticulocyte lysate cell-free system in the absence of exogenous membranes

In a rabbit reticulocyte lysate cell-free system and using double antibody immunoprecipitation method, newly translated rat liver NADPH-cytochrome P-450 reductase (E.C. 1.6.2.4) was shown to be cleaved in the absence of exogenous membranes. Reductase having a Mr = 78,000 was shown to be converted to a Mr = 67,000 upon incubation with either lysate or antisera. Peptide maps of 78,000 dalton reductase and 67,000 dalton protein were identical except for three additional peptides present in the 78,000 dalton reductase map. The cleavage activity associated with the antisera could be prevented by using the IgG fraction, while that associated with the lysate was inhibited by using the protease inhibitors leupeptin, pepstatin or bestatin.