The Role of Components of the Endoplasmic Reticulum in the Biosynthesis of CytochromeP-450

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Abstract
Antibodies were prepared to rat hepatic cytochrome P-450 and their specificity demonstrated. The antibodies were used to investigate the biosynthesis of cytochrome P-450 in vitro and in situ in various components of the endoplasmic reticulum. A preparation of heavy rough endoplasmic reticulum translocates proteins newly biosynthesized in vitro vectorially into the luminal space where they are released by low concentrations of deoxycholate. A significant proportion of the radioactivity found in this released fraction is incorporated into cytochrome P-450. Following incorporation of [14C]leucine by perfused rat liver, radioactively labeled cytochrome P-450 is found in the intracisternal content of heavy rough, light rough and smooth endoplasmic reticulum and in a solubilized Golgi preparation. At least part of the newly biosynthesized cytochrome P-450 is apparently translocated into the intracisternal space of the rough endoplasmic reticulum and then passes through the other components of the endoplasmic reticulum before insertion at its ultimate membrane locus.