STUDIES ON THE INCORPORATION OF ARGININE 



305 



formation of arginine-RNA is independent of arginine concentrations 

 above o • i mM. 



As a qualitative test of the product formed, a sample of acceptor RNA 

 from 30S0A5 was labelled with the more active of the ["C]-arginine 

 preparations (see Methods and Materials). The labelled RNA obtained 

 had a specific activity of 5730 c.p.m./o.u. It was subjected to mild alkaline 

 treatment (0-05 M triethylamine for 3 min. at 60°) and analyzed by paper 

 chromatography. Only the arginine spot could be detected, despite the 

 fact that the arginine used for the incorporation experiment showed four 

 spots of impurities. 



The hydrolysis of arginine-RNA at pH 8-o was studied at three 

 temperatures. Samples of p^C]-arginine-RNA with 160 c.p.m./o.u. were 

 incubated at different temperatures; aliquots were removed at various 



Fig. 5. 



20 30 40 50 60 

 Time (min) 

 Rate of hydrolysis of arginine-RNA at pH 8 -o and different temperatures. 



times and added to i ml. of cold o-oi M lanthanum nitrate in 0-5 M per- 

 chloric acid. The precipitate collected after centrifugation was counted. 

 Figure 5 shows these data as a percentage of the counts of the zero time 

 precipitate. 



Discussion 



THE ARGININE-ACTIVATING ENZYME 



The chromatography of the arginine-activating enzyme described here 

 removes nucleic acid rather well but gives on a protein basis only about a 

 threefold increase in specific activity. However, the amount of protein 

 required to label i mg. of RNA in 15 min. is only 15 fig. (see Fig. 4). The 

 corresponding figure for a seven-times purified leucine-activating enzyme 

 calculated from Fig. 3 in ref. [16] was found to be around 4-7 mg. A 

 similar figure has been reported also for an isoleucine-activating protein 



