Table 1.
Folding parameters of GB1 as a function of pH
| pH | kDI (s−1) | kNI/(1 + Kpart) (s−1) | Kpart | ΔGD-N∗ (kcal mol−1) | ΔGD-N† (kcal mol−1) |
|---|---|---|---|---|---|
| 2.0 | 1000 ± 90 | 11.0 ± 3.0 | 1.7 ± 0.2 | 2.7 ± 0.3 | 3.9 ± 0.8 |
| 2.5 | 1000 ± 90 | 19.2 ± 4.8 | 3.0 ± 0.4 | 2.3 ± 0.2 | 3.0 ± 0.7 |
| 3.0 | 1050 ± 95 | 5.2 ±1.3 | 0.9 ±0.1 | 3.1 ± 0.4 | 3.8 ± 0.4 |
| 3.5 | 1200 ± 120 | 5.1 ±1.3 | 1.2 ±0.1 | 3.2 ± 0.2 | 3.9 ± 0.4 |
| 4.0 | 1400 ± 120 | 1.3 ± 0.3 | 0.42 ± 0.09 | 4.1± 0.2 | 4.5 ± 0.4 |
| 4.5 | 1800 ± 170 | 0.4 ± 0.1 | 0.20 ± 0.04 | 5.0 ± 0.2 | 4.2 ± 0.4 |
| 5.0 | 1300 ± 120 | 0.15 ± 0.04 | 0.09 ± 0.02 | 5.3 ± 0.2 | 4.9 ± 0.5 |
| 5.5 | 1370 ± 100 | 0.15 ± 0.04 | 0.13 ± 0.03 | 5.4 ± 0.1 | 4.6 ± 0.5 |
| 6.0 | 720 ± 70 | 0.12 ± 0.03 | 0.09 ± 0.02 | 5.1 ± 0.1 | 5.2 ± 0.5 |
| 6.5 | 830 ± 70 | 0.14 ± 0.04 | 0.10 ± 0.02 | 5.1 ± 0.2 | 4.7 ± 0.5 |
| 7.0 | 670 ± 70 | 0.19 ± 0.05 | 0.12 ± 0.02 | 4.8 ± 0.2 | 5.3 ± 0.5 |
| 7.5 | 630 ± 70 | 0.27 ± 0.07 | 0.11 ± 0.02 | 4.6 ± 0.2 | 4.3 ± 0.4 |
| 8.0 | 600 ± 60 | 0.4 ± 0.1 | 0.12 ± 0.03 | 4.3 ± 0.3 | 4.3 ± 0.4 |
| 8.5 | 500 ± 40 | 0.6 ± 0.2 | 0.11 ± 0.02 | 3.9 ± 0.2 | 3.8 ± 0.4 |
| 9.0 | 390 ± 40 | 0.9 ± 0.2 | 0.13 ± 0.03 | 3.6 ± 0.2 | 3.3 ± 0.3 |
| 9.6 | 220 ± 25 | 1.3 ± 0.3 | 0.11 ± 0.02 | 3.0 ± 0.2 | 3.0 ± 0.3 |
Calculated from chevron plot analysis. The Chevron plots were fitted globally to a three-state model with shared m-values. kDI is the microscopic rate constant for the formation of the intermediate from the denatured state; kNI is the microscopic rate constant for the unfolding of the native state to the intermediate state; Kpart is the partitioning factor kID/kIN reflecting the difference between the activation barriers for the intermediate to revert to the reagents rather than proceeding to the products. The analysis returned a total mD-N = 1.95 ± 0.2 kcal mol−1 M−1. The Tanford β-values for the two transition states were βTS1 = 0.76 ± 0.04 and βTS2 = 0.93 ± 0.04.
Calculated from equilibrium denaturation. Equilibrium denaturations were fitted both individually and globally with shared mD-N value. The global analysis returned mD-N = 1.75 ± 0.2 kcal mol−1 M−1. This value was consistent within error with the values obtained by fitting individually each independent equilibrium experiments, as well as with the value calculated from kinetic experiments.