Table 2.
ITC Parameters Recovered for Tb3+ Displacement of Ca2+ from EF-Hands of CaM and DREAM Using a Sequential Modela
| K1 × 104 | K2 × 104 | K3 × 104 | ΔH1 | ΔH2 | ΔH3 | TΔS1 | TΔS2 | TΔS3 | |
|---|---|---|---|---|---|---|---|---|---|
| CaM | 29 ± 4.2 | 0.7 ± 0.4 | 5.1 ± 8.4 | 12 ± 5 | 212 ± 38 | −307 ± 127 | 19 ± 3.9 | 217 | −302 |
| CaM with Mg2+ | 8.9 ± 1.8 | 1.9 ± 0.2 | 1.4 ± 0.2 | 13 ± 1.5 | 47 ± 0.6 | 23 ± 7 | 20 ± 1.4 | 52 ± 0.6 | 28 ± 7 |
| DREAM(Δ64) | 22 ± 1.3 | 8.1 ± 1.6 | 2.8 ± 0.2 | 13 ± 9.0 | 18 ± 0.6 | −2.5 ± 2.7 | 20 ± 9.1 | 24 ± 0.4 | 3.6 ± 2.7 |
| DREAM(Δ64) with Mg2+ | 16 ± 2.5 | 11 ± 1.1 | 6.0 ± 0.5 | 12 ± 1.3 | 18 ± 6.0 | 3.4 ± 3.2 | 19 ± 1.3 | 25 ± 5.9 | 9.9 ± 3.1 |
| DREAM (Δ160) | 6.9 ± 3.2 | 8.9 ± 9.2 | 13 ± 1.7 | 8.2 ± 1.3 | 19 ± 1.5 | 15 ± 1.1 | |||
| DREAM (Δ160) with Mg2+ | 6.8 ± 1.4 | 1.8 ± 0.6 | 11 ± 2.2 | 7.7 ± 2.4 | 17 ± 2.1 | 14 ± 2.4 | |||
| DREAM (E186Q) with Mg2+ | 14.0 ± 0.9 | 8.6 ± 1.3 | 8.8 ± 2.2 | 7.5 ± 1.2 | 15 ± 1.7 | 2.2 ± 2.6 | 14 ± 0.8 | 22 ± 1.8 | 9 ± 2.7 |
| DREAM (E234Q) with Mg2+ | 5.7 ± 0.9 | 27 ± 1.5 | 16 ± 6.2 | 11 ± 1.9 | 3.6 ± 2.7 | 4.0 ± 1.3 | 18 ± 1.9 | 9.6 ± 2.5 | 11 ± 0.9 |
a
All experiments were conducted in triplicate at 25 °C; errors are standard deviations. Enthalpy and entropy changes shown in units of kilocalories per mole; association constants in units of inverse molar.