Sso7d is a 62-residue, basic protein from the hyperthermophilic archaeon Sulfolobus solfataricus. Around neutral pH, it exhibits a denaturation temperature close to 100 °C and a non-sequence-specific DNA binding activity. Here, we report the characterization by circular dichroism and fluorescence measurements of a variant form of Sso7d truncated at leucine 54 (L54Δ). It is shown that L54Δ has a folded conformation at neutral pH and that its thermal unfolding is a reversible process, represented well by the two-state N ⇔ D transition model, with a denaturation temperature of 53 °C. Fluorescence titration experiments indicate that L54Δ binds tightly to calf thymus DNA, even though the binding parameters are smaller than those of the wild-type protein. Therefore, the truncation of eight residues at the C-terminus of Sso7d markedly affects the thermal stability of the protein, which nevertheless retains a folded structure and DNA binding activity.
Shehi, E., Granata, V., Del Vecchio, P., Barone, G., Fusi, P., Tortora, P., et al. (2003). Thermal stability and DNA-binding activity of a variant of the Sso7d protein form the archeon Sulfolobus solfataricus truncated at leucine 54. BIOCHEMISTRY, 42(27), 8362-8368 [10.1021/bi034520t].
Thermal stability and DNA-binding activity of a variant of the Sso7d protein form the archeon Sulfolobus solfataricus truncated at leucine 54
FUSI, PAOLA ALESSANDRA;
2003
Abstract
Sso7d is a 62-residue, basic protein from the hyperthermophilic archaeon Sulfolobus solfataricus. Around neutral pH, it exhibits a denaturation temperature close to 100 °C and a non-sequence-specific DNA binding activity. Here, we report the characterization by circular dichroism and fluorescence measurements of a variant form of Sso7d truncated at leucine 54 (L54Δ). It is shown that L54Δ has a folded conformation at neutral pH and that its thermal unfolding is a reversible process, represented well by the two-state N ⇔ D transition model, with a denaturation temperature of 53 °C. Fluorescence titration experiments indicate that L54Δ binds tightly to calf thymus DNA, even though the binding parameters are smaller than those of the wild-type protein. Therefore, the truncation of eight residues at the C-terminus of Sso7d markedly affects the thermal stability of the protein, which nevertheless retains a folded structure and DNA binding activity.
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