Effect of Various Inhibitors on Nuclear Protein Synthesis in Rat Liver

During the past decade it has become clear that in cells of higher organisms most protein synthesis is mediated by polysomes occurring free in the cytoplasm or attached to the endoplasmic reticulum. There is ample evidence, however, that synthesis of proteins may also occur at other loci within the cell ; for example, in mitochondria (1-3), in chloroplasts (4-6), and in the nucleus (7-11) . Protein synthesis in both mitochondria and chloroplasts differs from that occurring elsewhere in the cytoplasm, resembling, rather, that of bacterial systems . Thus, ribosomes from mitochondrial and chloroplasts, like those of bacteria, are smaller than those from microsomal systems