TABLE 4.
Thermal stability of antithrombin P14 variants
The thermal stabilities of antithrombin P14 variants were measured from melting curves of the variants monitored by tryptophan fluorescence changes as a function of temperature as described under “Experimental Procedures.” Tm was obtained by fitting melting curves by Equation 11 as shown in the text. Data represent average values from at least two melting curves with errors representing the range of observed values. ND indicates that a value was not determined.
| P14 variant | Tm | Tm, mut- Tm, WT | ΔΔG0 |
|---|---|---|---|
| °C | °C | kcal/mol | |
| Val | 58.3 ± 0.1 | 2.7 ± 0.4 | 1.7 ± 0.5 |
| Thr | 56.9 ± 0.2 | 1.3 ± 0.5 | 0.8 ± 0.4 |
| Ala | 57.8 ± 0.2 | 2.2 ± 0.5 | 1.3 ± 0.5 |
| Leu | 55.3 ± 0.2 | −0.3 ± 0.5 | −0.2 ± 0.3 |
| Met | ND | ND | ND |
| Ser (WT) | 55.6 ± 0.3 | 0 | 0 |
| Trp | ND | −5.5 ± 0.4a | −3.4 ± 0.3 |
| Phe | 52.6 ± 0.2 | −3.0 ± 0.5 | −1.8 ± 0.1 |
| Gly | 53.5 ± 0.1 | −2.1 ± 0.4 | −1.3 ± 0.05 |
| Pro | 50.7 ± 0.2 | −4.9 ± 0.5 | −3.0 ± 0.2 |
| His | 50.5 ± 0.3 | −5.1 ± 0.6 | −3.1 ± 0.1 |
| Tyr | 50.3 ± 0.3 | −5.3 ± 0.6 | −3.2 ± 0.1 |
| Gln | 51.7 ± 0.3 | −3.9 ± 0.6 | −2.4 ± 0.1 |
| Asp | 53.4 ± 0.7 | −2.2 ± 1.0 | −1.3 ± 0.4 |
| Glu | 51.8 ± 0.6 | −3.8 ± 0.9 | −2.3 ± 0.2 |
| Arg | 48.6 ± 0.3 | −7.0 ± 0.6 | −4.3 ± 0.3 |
a Value was taken from Ref. 13.