FIGURE 4.
tRNA modification and binding preferences for TrmB. (A) Single-turnover modification by 5 µM TrmB and 50 µM [3H]SAM mixed with 1 µM unmodified tRNAPhe (open circles), tRNAPhe m5U54 (purple triangles), or tRNAPhe Ψ55 (blue circles). The average apparent rate of modification from three time courses (one representative each shown here) is reported in Table 2. TrmB binding to 20 nM (B) unmodified tRNAPhe (open circles), tRNAPhe m5U54 (purple triangles), tRNAPhe Ψ55 (blue circles), or to (C) unmodified tRNAPhe (black circles, same as shown in B), tRNAPhe m5U54 Ψ55 (gray squares, dashed line), or tRNAPhe m7G46 (open squares, dashed line). The experiments were repeated at least three times, and the average KD for each tRNA is summarized in Table 3.