Studies on the effects of inhibitors upon the transfer of radioactivity from prelabelled silkgland cell debri to particulate protein have been developed. The role of lipid fraction in the protein synthesis has also been studied and discussed.
1. At the transfer of radioactivity from prelabelled cell debris to particulate protein, RNA, DNA and deoxycholate-soluble lipoidal materials were required, whereas the addition of chloramphenicol (10
-4M), nitrogen mustard (10
-5M) and 2, 4-dinitrophenol (10
-4M) caused no inhibitory effect upon the transfer mechanism.
2. From the time course incubations performed with minced silkglands it seems difficult to find out any particular causal relation between cell debris protein and particulate or supernate protein. And the protein-bound radioactivity in cell debris might not be associated with the transfer reaction.
3. Slices of normal and regenerating rat liver showed a relatively high incorporation of C
14-amino acids in to lipid fraction compared with that of the protein fraction. However, in the tissues showing excellent protein synthesis such as silkworm's posterior silkglands and rat ascites hepatoma cells, the incorporation of C
14-amino acids into lipids was by far at a lower rate than that of the protein. No initial marked uptake of radioactivity into lipid fraction was observed.
4. When the silkgland cell debris were preliminary treated by sodium deoxycholate, the transfer of radioactivity was markedly suppressed although their radioactivity was almost completely preserved.
Thus, as for the role of lipids in the protein synthesis in silkglands, it might be supposed that the lipid fraction is not a direct precursor of protein, but mediates the transfer reaction.
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