38. BIOSYNTHESIS OF PROTEINS IN BACTERIAL CELLS 413 



TABLE I 



Composition of the RNA Amino Acid Pool at Saturation After Addition of 



Various Amino Acids to a Growing Culture of E. coli 



Amino Acids 



RNA 



(nuxmoles/mg.) 



Proline 0.8 



Tyrosine 6.0 



Phenylalanine 0.12 



Methionine 0.15 



Valine 0.20 



Isoleucine 0.27 



Leucine 0.19 



enzymes have been isolated in pure form, each of them being specific for a 

 single amino acid. 33 " 38 The cytological distribution of these enzymes is not 

 known as they are not found specifically bound to any subcellular frac- 

 tions. 



The bacterial species studied so far seem to contain a "soluble" or "non- 

 centrifugable" fraction of RNA, which functions as an amino acid acceptor 

 in vitro™ • 40 as well as in vivo. 41 



In E. coli, this sRNA represents approximately 10 to 20% of the total 

 RNA, the remainder being particulate. 4243 Its base composition differs 

 very much from that of the "bulk RNA." It contains large quantities of 

 cytosine; and about 15 % of its bases are atypical. When single radioactive 

 amino acids are added to cultures of E. coli, a complex is formed between 

 the corresponding amino acid and RNA 41 as occurs also in animal material 30 

 (Chapter 37). 



The kinetics of formation will be considered later (see Section III). The 

 composition at saturation for seven amino acids is represented in Table I. 



33 E. W. Davie, V. V. Koningsberger, and F. Lipmann, Arch. Biochem. Biophys. 65, 

 21 (1956). 



34 R. S. Schweet, Federation Proc, 16, 244 (1957). 



35 R. D. Cole, J. Coote, and T. S. Work, Nature 179, 199 (1957). 



36 R. W. Holley, Federation Proc, 17, 964 (1958). 



37 P. Berg, J. Biol. Chem. 222, 1025 (1956). 



38 R. S. Schweet, R. W. Holley, and E. H. Allen, Arch. Biochem. Biophys. 71, 311 

 (1957). 



39 P. Berg and E. J. Ofengand, Proc. Natl. Acad. Sci. U. S. 44, 78 (1958). 



40 T. Erdos and A. Ullmann, Nature 183, 618 (1959). 



41 S. Lacks and F. Gros, J. Mol. Biol. 1, No. 4.5, p. 301 (1959). 



42 A. B. Pardee, K. Paigen, and L. S. Prestige, Biochim. et Biophys. Acta 23, 162 

 (1957). 



43 M. Nomura and J. D. Watson, J. Mol. Biol. 1, 204 (1959). 



