TABLE 1.
Thermodynamic parameters for the binding of wild-type and mutant EphA4 to ephrin-B2 and two small molecule antagonists measured by ITC
All measurements were performed in 10 mm phosphate buffer, pH 6.2, with an injection volume of 5 μl.
| Syringe | Cell | Ka | Ka | Stoichiometry | ΔS | ΔH |
|---|---|---|---|---|---|---|
| m−1 | μm | n | cal/mol·K | kcal/mol | ||
| EphA4 (0.2 mm) | Ephrin-B2 (0.01 mm) | 4.93 × 106 ± 0.47 × 106 | 0.203 | 1.00 ± 0.00 | 20.9 | −2.89 ± 0.035 |
| Mutant EphA4 (0.6 mm) | Ephrin-B2 (0.03 mm) | 4.2 × 105 ± 0.55 × 105 | 2.35 | 0.92 ± 0.02 | 19.7 | −1.81 ± 0.053 |
| Compound 1 (2 mm)a | EphA4 (0.07 mm) | 4.89 × 104 ± 0.51 × 104 | 20.4 | 1.00 ± 0.00 | 18.1 | −1.00 ± 0.027 |
| Compound 1 (2 mm) | Mutant EphA4 (0.07 mm) | 4.95 × 104 ± 0.31 × 104 | 20.2 | 1.20 ± 0.00 | 19.8 | −0.51 ± 0.008 |
| Compound 2 (2 mm)a | EphA4 (0.07 mm) | 3.78 × 104 ± 0.76 × 104 | 26.4 | 1.00 ± 0.00 | 20.1 | −0.24 ± 0.013 |
| Compound 2 (2 mm) | Mutant EphA4 (0.07 mm) | 3.93 × 104 ± 0.21 × 104 | 25.4 | 0.98 ± 0.00 | 20.4 | −0.19 ± 0.003 |
a ITC data for the binding of compounds 1 and 2 to wild-type EphA4 from a previous publication (7) are included for comparison.