37. NUCLEIC ACID AND PROTEIN SYNTHESIS 

 _ microsome protein 



389 



5 10 15 



MINUTES 



Fig. 5. The transfer of leucine-C 14 from whole leucine-C 14 labeled pH 5 fraction 

 to microsomal protein. The open circles are the c.p.m. in transfer RNA, the closed 

 the c.p.m. in particle protein. [From M. B. Hoagland, M. L. Stephenson, J. F. Scott, 

 L. I. Hecht, and P. C. Zamecnik, Biochim. et Biophys. Acta 24, 215 (1957).] 



-AMP IN M-RNA 



C -VALINE IN M-RNA 



4 6 8 



MINUTES 



Fig. 6. Transfer of amino acid and terminal adenine from transfer RNA to ribo- 

 somal RNA, and of amino acid to ribosomal protein. The system consisted of yeast 

 soluble RNA, dialyzed ascites tumor S4 fraction, rat liver microsomes, ATP, GTP, 

 and a nucleoside triphosphate generating system. The yeast soluble RNA was labeled 

 in one case (the two lower curves) with valine-C 14 and in the other (upper curve) with 

 AMP-C 14 in the terminal position. After incubation at 21°C. the microsomes were 

 reisolated centrifugally and their RNA and protein isolated and counted. [Data are 

 from P. C. Zamecnik, Harvey Lectures 64, 256 (I960).] 



RNA amino acid was limiting, all of the labeled amino acid was trans- 

 ferred to protein. 96 This means that all of the sites on RNA occupied by- 

 ami no acids are metabolically competent in the sense that they are able 

 to participate in the reactions which bring about the transfer of their 



