Vol. 45, 1959 



BIOCHEMISTRY: KORNBERG ET AL. 



779 



TABLE 1 

 Specificity op^ the Enzyme which Glucosylates DNA 



Expt. 

 No. Conditions 



1 Complete system (10 m/xmoles of C'^-UDPG) 



Add C»2-UDPG (10 m/imoles). 



Add C"'-glucose (200 m^moles) 



Add Ci2-glucose 1-P (200 mMmoles) 



Add Ci2-glucose 6-P (250 m/imoles) 



Replace UDPG with C'''-glucose (10 m/xmoles) 



Replace UDPG with C'^-glucose 6-P (12 m/imoles) 



2 Complete system (DNA containing 0.46 m/tmole of HMC) 



Replace HMC-DNA with cytosine-DNA (containing 0.75 



m/xmole cytosine) 

 Replace HMC-DNA with T2 DNA (containing 2 m^moles 



HMC) 



The complete system had the composition and was treated as described in Figure 4, using a 

 30-fold purified enzyme, 0.3 fig in E.xpt. 1 and 1.5 ng in Expt. 2. In each case the DNA was 

 glucosylated to its limit (see Fig. 5). 



* The glucose fixed is calculated on the basis of the specific radioactivity of the UDPG after dilution of the C" 

 sample with Ci'-UDPG. 



1.0 2.0 3.0 4.0 



HMC-DNA -m/^, Moles of HMC 



Fig. 5. —Limit of glucose fixation in DNA as a function of the amount 

 of DNA added. The experimental details were as in Fig. 4, using the 

 partially purified enzyme. The HMC-DNA was prepared with thy- 

 mus DNA as primer. 



a given sample of HMC-DNA as distinctive for the type of primer used in the 

 enzymatic synthesis of the HMC-DNA. Further studies are required to determine 

 how conditions of enzymatic polymerization, as well as the isolation of the DNA, 

 may influence the glucose/HMC ratios obtained. 



132 



