FIG. 3.

ATPase and helicase activities of M. tuberculosis UvrD. (A) UvrD ATPase activity was assayed on 10 μM poly(T)₁₈ with 100 nM UvrD in the presence of 2 mM ATP. (B) Polarity of unwinding of M. tuberculosis UvrD. Reaction mixtures containing 1 mM ATP, 5 mM MgCl₂, 1 nM ³²P-labeled helicase substrates (as depicted at the top), and 200 nM UvrD were incubated for 20 min at 37°C. The reaction mixtures were analyzed by native PAGE. HD, heat-denatured substrates. The asterisks indicate the ³²P label. (C) Effect of the length of the 3′-ssDNA tail on UvrD helicase activity. Reaction mixtures containing 1 mM ATP, 5 mM MgCl₂, 1 nM ³²P-labeled helicase substrates, and 200 nM UvrD were incubated for 20 min at 37°C. The reaction mixtures were analyzed by native PAGE. HD, heat-denatured substrates. The asterisk indicates the ³²P label.