VmUS-INDUCED ACQUISITION OF METABOLIC FUNCTION 



19 



Hershey and Melechen, 1957) that the early synthesis of protein was 

 essential to the synthesis of viral DNA. Indeed, once this protein was 

 made, the inhibition of further protein synthesis did not block the 

 production of functionally active viral DNA (Burton, 1955; Hershey 

 and Melechen, 1957). It could therefore be asked what function was 

 fulfilled by this early protein, which was not itself a component of virus 

 but was nevertheless essential to the production of viral DNA. One 

 obvious suggestion was that the early protein was involved in the 

 formation of HMC. Having conceded the possibility of the expansion 

 of the metabolic machinery, it could also be suggested that other en- 

 zymes might be made, particularly those which might account for the 

 enormous stimulation of DNA synthesis observed on infection. 



In Figure 1 it can be seen that there is no net synthesis of RNA. 

 The use of radioactive phosphorus ( P^- ) then showed an incorporation 

 of this isotope into the RNA fraction which was only 2 per cent of the 

 incorporation into DNA ( Cohen, 1947 ) . This result has been confirmed 

 many times, but although it was initially concluded that this amount of 

 isotope in the RNA fraction reflected a contamination of the RNA, 

 Volkin and Astrachan ( 1957 ) have shown rigorously that the labeled 

 phosphorus is indeed in RNA. This newly synthesized material is a 



APPEARANCE of INTRACELLULAR 

 1 RNA PHAGE 



' I I I 



10 15 20 25 



MINUTES 



Figure 1. Time course of polymer syntheses in E. coli infected by T-even 

 phages. 



