VmUS-INDUCED ACQUISITION OF METABOLIC FUNCTION 



29 



90-- 



80-- 



70-- 



60- 



50-- 



40-- 



z 

 o 

 I- 

 m 30-- 



i 

 z 



ae 20-- 



10- 







F-dUMP 



-7 -6 -5 -4 -3 



LOG CONCENTRATION 



Figure 6. The inhibition of two fluorouracil nucleotides on thymidylate syn- 

 thetases induced by chemically different DNAs. F-dUMP = Fluorodeoxy- 

 uridine-5'-phosphate. F-aUMP = D-arabinofuranosyl fluorouracil-5'-phos- 

 phate. 



infect strain Bt-, and the cytosine-containing DNA of TS." It was 

 therefore of interest to see if the three forms of the enzyme were dif- 

 ferent, and the two inhibitors, F-dUMP and F-aUMP, were used to 

 compare the sensitivities of the active sites of the enzyme in extracts of 

 strain B and of virus-infected Bt-. Miss H. D. Barner has recently im- 

 proved the assay very considerably for these experiments. As can be 

 seen in Figure 6, the active sites of the bacterial enzyme and two 



* Of course we cannot state that there are chemical differences between the 

 fractions of E. coli DNA and T5 DNA which control the production of this en- 

 zyme, but the over-all compositions of the total DxXAs of these forms are quite 

 different (Wyatt and Cohen, 1953). 



