Figure 4.

Cleavage of chimeric RNA–DNA junction substrates. Reaction mixtures (10 μl) containing 25 mM Tris–HCl (pH 7.5), 50 mM NaCl, 5 mM MgCl₂, 20 nM (200 fmol) ³²P-labeled 24-mer duplexes R24, R12D12 or D12R12 (shown at the bottom, with the ³²P label denoted by • and the ribonucleotides depicted in white on a black background), and 8 nM (80 fmol) RnhA (where indicated by +) were incubated for 20 min at 37°C. The products were resolved by urea-PAGE and visualized by autoradiography. Alkaline hydrolysis ladders of ³²P-labeled R24, R12D12 and D12R12 strand were analyzed in parallel in the three lanes on the left (^–OH).