38. BIOSYNTHESIS OF PROTEINS IN BACTERIAL CELLS 



425 



RN A 



5000 



200 



A 8 12 16 20 



minutes 



Fig. 3. Effect of chloramphenicol (Chloromycetin) on the incorporation of meth- 

 ionine-S 35 into the RNA and protein of E. coli ML 30 chloramphenicol (21 /ig./ml.); 

 DL-methionine-S 3S (4.10~ 5 M), specific radioactivity (2 /xc./Mmole). 



If the kinetics of renewal of amino acids bound to the total RNA (Figs. 

 2 and 3) represent, in fact, the rate at which both the sRNA and the RNA 

 particulate are simultaneously or sequentially labeled, (rather than the ex- 

 clusive labeling of the sRN A) , another entirely different interpretation of data 

 in Fig. 3, is possible. They could suggest that Chloromycetin slows down 

 the rate of incorporation of amino acids into the RNA particulate while 

 the size of the sRNA amino acid pool would slowly increase above normal 

 values, due to the fact that acceptor sites on the sRNA would not be en- 

 tirely saturated and that Chloromycetin would inhibit transfer of amino 

 acids from the sRNA to the RNA particulate. The choice between these 

 interpretations has to wait for studies on amino acid incorporation into 

 separated fractions of RNA. Whatever the correct interpretations may 

 be, displacement of a radioactive amino acid fixed on RNA by an excess 

 of the corresponding unlabeled amino acid gives rise to an almost equiva- 

 lent increase in the radioactivity of the protein fraction. The results of 

 such a "transfer experiment" are given in Table III. Gale 114 obtained simi- 

 lar results using preparations of disrupted Staphylococcus aureus. 



The question as to whether all the proteins are formed via the "activat- 

 ing" systems and the sRNA, or whether other pathways for amino acid 

 incorporation into protein exist will be discussed later. 



E. F. Gale, 7th Intern. Congr. Microbiol., Stockholm Symposium 2, p. 104 (1958). 



