FIG. 6.

The effect of inhibitors and allosteric effectors on RRase activity. For all reactions 180 μg of total crude cell extract was used (60 μg of NrdA, 120 μg of NrdB), and the results are given as percentages of the activity with positive effector ATP (1 mM) alone, which corresponded to 5.6 U. (A) Effect of increasing concentrations of hydroxyurea on the reduction of CDP by B. fragilis RRase. The results are given as percentages of the activity in the absence of hydroxyurea. (B) Effect of purine deoxynucleoside triphosphates (1 mM) on the activity of B. fragilis RRase in the presence of positive effector ATP (1 mM).