FIGURE 5.

Stoichiometry of AMP and aa-tRNA^Leu production in the presence of Leu or Nva in parallel steady-state reactions by WT and mutant EcLeuRS enzymes. Time courses following [³²P]AMP production are illustrated by filled symbols, and time courses following aa-[³²P]tRNA^Leu production are illustrated by open symbols. A–D represent parallel production of [³²P]AMP and Nva-[³²P]tRNA^Leu by 10 nm WT, T252R, D345A, or T252R/D345A LeuRS, respectively. Because of the low Nva-tRNA^Leu accumulation by WT LeuRS, the formation rate of 0.03 s⁻¹ (A) should be taken as an approximate value. E–H represent parallel production of [³²P]AMP and Leu-[³²P]tRNA^Leu by 5 nm WT, T252R, D345A, or T252R/D345A LeuRS, respectively. The rate constants represent the best fit value ± S.E. of three independent experiments.