Table 3. Thermodynamic parameters of the six Kyrpides, Ouzounis, Woese (KOW) domains.
The values were derived from chemical denaturations monitored by circular dichroism (CD) spectroscopy as well as fluorescence spectroscopy where indicated. Standard deviations result from data fitting.
| Parameter | EcNusG-KOW | MtNusG-KOW | MjSpt5-KOW | hSpt5-KOW5 | EcRfaH-KOW | VcRfaH-KOW |
|---|---|---|---|---|---|---|
| ΔGu(H2O) (25°C) (kJ/mol) | ||||||
| Urea, pH 4 | 19.8±2.21 | 22.4±3.46 | –* | 6.24±4.42 | – (native state aggregation) | 10.8±1.66 (10.8±0.90)† |
| Urea, pH 7 | 27.7±4.21 | 26.4±6.16 | –* | 14.3±2.90 | Three-state | 14.0±1.74 (13.9±0.61)† |
| GdmCl, pH 7 | 11.7±2.07 | 15.7±3.99 | 45.4±4.83 | 7.37±3.16 | Three-state | 2.87±4.92 (2.84±6.55)† |
| m (25°C) (kJ/(mol M)) ‡ | ||||||
| Urea, pH 4 | 2.51±0.453 | 4.18±0.660 | –* | 3.25±0.857 | – (native state aggregation) | 2.91±0.396 (2.98±0.22)† |
| Urea, pH 7 | 3.84±0.681 | 5.71±1.32 | –* | 3.83±0.820 | Three-state | 2.98±0.388 (3.13±0.14)† |
| GdmCl, pH 7 | 5.22±0.809 | 8.26±1.87 | 9.02±0.984 | 4.95±1.31 | Three-state | 7.71±3.68 (7.86±4.29)† |
| [Denat]1/2 (25°C) (M) | ||||||
| Urea, pH 4 | 7.89 | 5.36 | >10* | 1.92 | – (native state aggregation) | 3.71 (3.62)† |
| Urea, pH 7 | 7.21 | 4.62 | >10* | 3.73 | ~2.25/~4.25 | 4.70 (4.44)† |
| GdmCl, pH 7 | 2.24 | 1.90 | 5.03 | 1.49 | ~0.6/~1.3 | 0.37 (0.36)† |
*
No denaturation possible.
†
Values were determined by fluorescence-based unfolding experiments.
‡
The m value is a measure of the broadness of the transition and correlates with the difference in the accessible surface area between N and U, and the transition midpoint.