Fig. 5.

Combined GluRS^ND and GatDE reactions. (a) TLC plate showing transient accumulation of the Glu-tRNA^Gln intermediate during conversion of tRNA^Gln to Gln-tRNA^Gln in the presence of both GluRS^ND (600 nM) and GatDE (600 nM). Plots of normalized data and kinetic simulation traces (not fits to data) for a two-step dissociative mechanism at 600 nM GluRS^ND and GatDE at 0 nM (a), 10 nM (b), 100 nM (c), 600 nM (d) and 6 μM (e). tRNA^Gln in all the reactions < 1 nM. The panels show that, at all tested concentrations of GatDE, a distributive model fits the data well. Goodness of fit values (R²) from the nonlinear regression were computed separately using GraphPad software; for formation and reaction of Glu-tRNA^Gln these values range from 0.91 to 0.97. See Supplementary Figs. S3–S5 for details of kinetic simulations and evidence that a channeling model does not fit the data.