Table 2. Dissociation constants (Kd) for the interaction between various CASTOR1/CASTOR2 constructs and various amino acids as measured by the isothermal titration calorimetry assay.
| CASTOR1/CASTOR2 | Amino acid | Molar ratio | Kd (μM) | ΔH (kcal mol−1) | TΔS (kcal mol−1) |
|---|---|---|---|---|---|
| WT CASTOR1 | Arginine | 1.01±0.10 | 2.23±0.20 | −13.4±1.7 | −6.05 |
| WT CASTOR1 | Lysine | ND | ND | ND | ND |
| WT CASTOR1 | Leucine | ND | ND | ND | ND |
| WT CASTOR2 | Arginine | ND | ND | ND | ND |
| CASTOR1-S111A | Arginine | 0.95±0.09 | 9.68±3.20 | −1.81±0.24 | 5.19 |
| CASTOR1-D304A | Arginine | ND | ND | ND | ND |
| S111A/D304A | Arginine | ND | ND | ND | ND |
Abbreviation: ND, no detectable interaction was observed.
±values, errors of curve fitting.