INDUCED ENZYME FORMATION 



The most extensive investigation on the properties of sub- 

 cellular fractions has come from Gale's (27,28) laboratory. In 

 these studies cells of Staphylococcus aureus are disrupted by sonic 

 disintegration and a fraction obtained by differential centrifu- 

 gation which is relatively low in viable cells, and therefore pre- 

 sumably in intact cells. Although it is unlikely that this prep- 

 aration is homogeneous, it nevertheless is of the greatest in- 

 terest, since it is amenable to enzymatic and extractive resolu- 

 tion. Removal of the nucleic acid from such disrupted cell 

 preparations leads to a marked lowering in their ability to in- 

 corporate amino acids. This loss can be restored by the ad- 

 dition of nucleic acids from the same species, DNA being more 

 active than RNA on a dry-weight basis. This latter finding 

 may be merely a consequence of the greater stability of DNA to 

 isolation procedures. The data are consistent with the concept 

 that the RNA made from the DNA supplied is the active 

 agent. 



A most interesting recent development has been the dis- 

 covery by Gale and Folkes (29) that the presence of specific 

 di- and trinucleotides is extremely active in promoting the in- 

 corporation of specific amino acids. Thus, for example, di- 

 nucleotides containing adenine and cytosine can completely re- 

 place the intact RNA in promoting the incorporation of aspartic 

 acid. Indeed, on an equivalent weight basis the dinucleotide is 

 more than a hundred times as active as the intact RNA. Inter- 

 pretation of these findings is yet uncertain. It may indeed be, 

 as suggested by Gale and Folkes (29), that these small fragments 

 represent that part of the RNA template which is concerned with 

 the insertion of the corresponding amino acid into peptide link- 

 age. An argument which can be raised against this assertion 

 stems precisely from the observed high activity of the dinucleo- 

 tide. It seems unlikely that nucleotide pairs are sufficient to 

 specify the relevant amino acids, since only 16 possibilities are 

 uniquely determined. At least three bases of the RNA tem- 

 plate would have to be involved in the specification of a given 

 amino acid since 20 or more choices have to be made. This rea- 



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