178 E. F. Gale 



incubation mixture. The action of added nucleic acid is to 

 increase both the rate of incorporation and the amount of 

 amino acid incorporated by the time the process ceases. 

 Restoration can be brought about by the presence of either 

 DNA or RNA but the latter is always less effective than the 

 former; optimal concentrations of RNA normally restore 

 incorporation to 50-70 per cent of the value obtained in the 

 presence of optimal concentrations of DNA. Of a variety of 

 nucleic acids tested in the staphylococcal system, only those 

 obtained from Staph, aureus proved to be effective. 



Modification of Nucleic Acid Component 



Whatever may be the mechanism of incorporation under 

 condition 1, it provides an experimental system in which a 

 relationship between proteins, amino acids and nucleic acids 

 can be investigated. 



Effect of digestion of nucleic acid. If staphylococcal DNA is 

 digested with deoxyribonuclease, the activity of the digest in 

 restoring glycine incorporation is less than that of the intact 

 nucleic acid and is further reduced on dialysis. If staphylo- 

 coccal RNA is digested with ribonuclease, the effect of the 

 digest in restoring glycine incorporation is greater than that 

 of the undigested RNA, the digest promoting incorporation 

 to the same level as that obtained in the presence of optimal 

 concentrations of DNA. Whereas the restoration by intact 

 RNA appears to be species specific, ribonuclease digests of 

 RNA from a variety of sources prove to be effective and the 

 active material in all cases is dialysable. 



Attempts have been made to fractionate RNA digests, 

 and activity in promoting incorporation has been found 

 associated with two types of fraction. When fractionation is 

 carried out according to the methods described by Markham 

 and Smith (1952) for the separation of small polynucleotides, 

 activity towards specific amino acids is found associated with 

 specific polynucleotide fractions, whereas activating sub- 

 stances of a relatively non-specific nature ("incorporation 



