AI Article Synopsis
- The archaeal histone-like protein Ssh10b from Sulfolobus shibatae was studied for its thermal unfolding properties using differential scanning calorimetry and circular dichroism spectroscopy.
- Ssh10b is identified as a stable dimer across a pH range of 2.5 to 7.0, with a maximum melting temperature of 99.9 degrees C, indicating it unfolds in a cooperative manner.
- The findings highlight a low specific heat capacity change during unfolding, resulting in a relatively low free energy change, which could affect the protein's stability in extreme environments where Sulfolobus thrives.
Article Abstract
The reversible thermal unfolding of the archaeal histone-like protein Ssh10b from the extremophile Sulfolobus shibatae was studied using differential scanning calorimetry and circular dichroism spectroscopy. Analytical ultracentrifugation and gel filtration showed that Ssh10b is a stable dimer in the pH range 2.5-7.0. Thermal denaturation data fit into a two-state unfolding model, suggesting that the Ssh10 dimer unfolds as a single cooperative unit with a maximal melting temperature of 99.9 degrees C and an enthalpy change of 134 kcal/mol at pH 7.0. The heat capacity change upon unfolding determined from linear fits of the temperature dependence of DeltaH(cal) is 2.55 kcal/(mol K). The low specific heat capacity change of 13 cal/(mol K residue) leads to a considerable flattening of the protein stability curve (DeltaG (T)) and results in a maximal DeltaG of only 9.5 kcal/mol at 320 K and a DeltaG of only 6.0 kcal/mol at the optimal growth temperature of Sulfolobus.
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| http://dx.doi.org/10.1016/j.bbrc.2008.06.030 | DOI Listing |
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