Thermal unfolding of the archaeal DNA and RNA binding protein Ssh10.

Journal article

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.

Authors: Wu, X; Oppermann, M; Berndt, K; Bergman, T; Jörnvall, H

• Publication status: Published
• Journal: Biochemical and biophysical research communications
• Volume: 373
• Issue: 4
• Pages: 482-487
• Publication date: 2008-09-01
• DOI: 10.1016/j.bbrc.2008.06.030
• EISSN: 1090-2104
• ISSN: 0006-291X
• Language: English
• Keywords: Molecular Sequence Data; RNA-Binding Proteins; Protein Folding; DNA-Binding Proteins; Histones; Thermodynamics; Hot Temperature; Amino Acid Sequence; Archaeal Proteins; Calorimetry, Differential Scanning; Sulfolobus; Protein Denaturation; Hydrogen-Ion Concentration; Circular Dichroism