Abstract
The investigation of the transfer of radio-activity from prelabelled cell debris to particulate fractions in the cell-free prepara-tions of the posterior silkgland was developped.
1. After labelling of silkglands with C14-glycine for 15 minutes in vivo or in vitro, posterior silkglands were collected and homogenized. The cell debris fraction was obtained by centrifugation at 700×g for 10 minutes. Microscopic observation of cell debris revealed that major components were nuclear debris and fragments of cell membranes without any intact cells.
2. Prelabelled cell debris thus prepared was highly radioactive and it was shown that under appropriate conditions, the radioactivity was transferred enzymatically to particulate protein. This was confirmed by dinitrophenylation study of isolated particles after the reaction.
3. Radioactivity was principally incorporated into protein of particulate fractions, but not very much into lipid and supernatant fractions.
4. As regards the transfer reaction, amino acid activating enzyme (E3) seemed to be unnecessary, whereas amino acids mixture, GTP, ATP and ATP-generating systems were required.
The work has been supported by grants partly from the Ministry of Education to the research group for Fibroin Biosynthesis and partly from the Rockefeller Foundation to one of the authors. We wish to thank Dr. K. Shimur a and his staff for their valuable discussion and Dr. B. Maruo for his kind supply of C14-all-labelled amino acids.
