FIGURE 3.

Comparison of standard free energies of the tRNA^Tyr aminoacylation reaction. The standard free energy for each tyrosyl-tRNA synthetase complex (relative to the free enzyme) was calculated. ΔG⁰ values for the 10–20, 20–25, and 25–35 °C temperature ranges were calculated from the ΔH⁰ and TΔS⁰ values presented in Table 1 using Equation 6. These temperature ranges were chosen based on the three discontinuous regions in Fig. 2, panel B. For cases where the natural logarithm of the rate or equilibrium constant is linear with respect to 1/T for two or more temperature ranges (e.g. ln(K_d^Tyr)), the same values for ΔH⁰ and TΔS⁰ were used for each temperature range. For the TyrRS·[Tyr-ATP]^‡ complex, the 20–25 and 25–35 °C temperature ranges are replaced by 20–29 and 29–35 °C. ΔG⁰ values labeled “Lit. Value” are calculated from literature values for the equilibrium and rate constants determined at 25 °C using Equations 15, 16, 17, 18, 19, 20, 21 (18).