168 !^AMECNiK et al. 



other fractions of the cell. This is particularly so for the mem- 

 branous, lipid-rich, deoxycholate-soluble portion of the 

 microsome fraction. In electron micrographs of intact liver 

 cells, these membranes are in close juxtaposition to the 

 ribonucleoprotein particles, where they may serve as acceptor 

 for a formed peptide chain, and as a site for its transformation 

 into a completed protein molecule or lipoprotein complex. 



Our evidence suggests therefore that protein synthesis in 

 the rat liver cytoplasm may be divided into three steps, as 

 indicated in Fig. 2. Further subdivisions remain tasks for the 

 future. 



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