In Vivo and In Vitro Incorporation of C14-L-Leucine by Various Cell Particles of Mouse Melanoma*

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Abstract
The incorporation of L-leucine-C14 by various cell particles of Harding Passey and B-16 mouse melanoma in-vivo and in-vitro was studied. The incorporation rate of leucine into ribosomes in-vivo was fast at the early stage after injection and reached its maximum at the end of 12 minutes and decreased thereafter. Smooth membranes which are thought to be a pre-stage of melanosomes, showed relatively fast incorporation. The incorporation by melanosomes was very slow and the amount incorporated was also very low, therefore, it is very unlike that the protein biosynthesis in melanosomes de-novo is so active. Ribosomes isolated from melanoma synthesize in-vitro the protein by the same mechanisms as liver ribosomes do. The rough membranes had high incorporating activity which was markedly inhibited by puromycin. By contrast the activity is very low in the smooth membranes. Melanosomes and deoxycholate (DOC)-treated melanosomes have the incorporating activity which is partially inhibited by puromycin and KF. This suggests that the melanosomes may possess the protein biosynthetic system in its structure.

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