FIG. 6.

Nonmethylated, isolated A loop: a minimal substrate for RrmJ in vitro. A 5 μM concentration of wild-type RrmJ was incubated with a 1 μM concentration of nonmodified (circles) or methylated (triangles) A loop (nucleotides 2545 to 2563) and 50 μM [³H]AdoMet (200 μCi/ml) in methylation buffer (50 mM HEPES-KOH [pH 7.5], 50 mM NaCl, 10 mM EDTA, 1 mM dithiothreitol, 40 U of RNasin, and 0.1 mg of bovine serum albumin/ml) at 37°C. Aliquots were taken at defined time points, and the [³H]methyl incorporation was measured as described previously.