TABLE 5.
Isothermal titration calorimetry data of monastrol binding different kinesin-5 motor domains in the presence of ATP
Data include the calculated number of binding sites (N), enthalpy and entropy values, and Kd. Averaged data from three replicates, each from three independent enzyme preparations, are shown. The ΔG values for the monastrol binding reaction of HsEg5 and Klp61F-L5 are both approximately −7 kcal/mol, whereas ΔG for monastrol binding to Klp61F-L5-α3 is approximately −5 kcal/mol. ND, not detectable.
| Motor domain | N | ΔH° | ΔS° | Kd |
|---|---|---|---|---|
| kcal/mol | cal mol−1K−1 | μm | ||
| HsEg5 | 0.89 ± 0.02 | −21.4 ± 1.8 | −49.5 ± 6.2 | 8.1 ± 0.5 |
| Klp61F-WT | ND | ND | ND | ND |
| Klp61F-L5 | 0.9a | −12.9 ± 2.3 | −20.3 ± 10.2 | 142.3 ± 11.7 |
| Klp61F-L5-α3 | 0.9a | −13.5 ± 1.9 | −29.7 ± 7.8 | 48.6 ± 1.2 |
a Although the ITC algorithms found the best fit to the single-site model in these cases, the weak binding curve necessitated fixing n = 0.9 to calculate the associated thermodynamic parameters.