Table 3.
Thermodynamic parameters of wild-type and mutant SdCen variants binding to XPC and Sfi1.
| ProteinC-SdCen | Ligand | Ca2+ | ΔH (error) (kcal/mol) | ΔΔHa (kcal/mol) | ΔG (kcal/mol) | ΔΔGb (kcal/mol) |
|---|---|---|---|---|---|---|
| WT | P17-XPC 30 °C | – | −33.8 (0.07) | – | −10.41 | – |
| 37 °C | – | −40.6 (0.12) | – | −10.66 | – | |
| F109L | P17-XPC 30 °C | – | −20.6 (0.09) | −13.2 | −8.72 | −1.69 |
| 37 °C | – | −23.16 (0.1) | −17.44 | −8.63 | −2.03 | |
| E144A | P17-XPC 30 °C | – | −29.5 (0.13) | −4.3 | −9.72 | −0.69 |
| 37 °C | – | −38.4 (0.17) | −2.2 | −9.74 | −0.67 | |
| F109L–E144A | P17-XPC 30 °C | – | −22.2 (0.2) | −11.6 | −7.81 | −2.6 |
| 37 °C | – | −21.2 (0.5) | −19.4 | −7.99 | −2.67 | |
| WT | R18-Sfi1 30 °C | – | −31.5 (0.08) | – | −9.26 | – |
| 37 °C | – | −37.09 (0.1) | – | −9.31 | – | |
| F109L | R18-Sfi1 30 °C | – | −23.2 (0.1) | −8.3 | −8.24 | −1.02 |
| 37 °C | – | −30.4 (1.0) | −6.69 | −8.1 | −1.21 | |
| E144A | R18-Sfi1 30 °C | – | −30.31 (0.06) | −1.19 | −9.25 | −0.01 |
| 37 °C | – | −36.22 (0.17) | −0.87 | −9.34 | +0.02 | |
| F109L–E144A | R18-Sfi1 30 °C | – | −24.4 (0.16) | −7.1 | −8.07 | −1.19 |
| 37 °C | – | −26.43 (0.3) | −10.66 | −8.19 | −1.12 |
The ITC experiments were conducted at 30 °C or 37 °C in buffer (MOPS 50 mM, NaCl 100 mM, EDTA 2 mM pH 7.5). N was the stoichiometry of binding. NB means no binding. The standard deviations of the fitted parameters are given in parenthesis.
a
The difference in binding enthalpy between the interaction of SdCen wt and P17-XPC and the interaction of SdCen mutants and P17-XPC, as well as for the SdC-R18-Sfi1 complexes.
b
The difference in free energy between the interaction of SdCen wt and P17-XPC and the interaction of SdCen mutants and P17-XPC, as well as for the SdC-R18-Sfi1 complexes.