ROLE OF COMPONENTS OF THE ENDOPLASMIC-RETICULUM IN THE BIOSYNTHESIS OF CYTOCHROME-P-450

Antibodies have been prepared to rat hepatic cytochrome P‐450 and their specificity demonstrated. These antibodies have been 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 bio‐synthesized in vitro vectorially into the luminal space and these 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 labelled cytochrome P‐450 can be found in the intracisternal content of heavy rough, light rough and smooth endoplasmic reticulum and also in a solubilized Golgi preparation. We suggest that at least part of the newly biosynthesized cytochrome P‐450 is 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. Copyright © 1979, Wiley Blackwell. All rights reserved