Thermal stability and DNA binding activity of a variant form of the Sso7d protein from the archeon Sulfolobus solfataricus truncated at leucine 54.
Sso7d is a 62-residue, basic protein from the hyperthermophilic archaeon Sulfolobus solfataricus. Around neutral pH, it exhibits a denaturation temperature close to 100 degrees 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 (L54Delta). It is shown that L54Delta 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 degrees C. Fluorescence titration experiments indicate that L54Delta 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
Erlet
E
Dipartimento di Biotecnologie e Bioscienze, Università di Milano-Bicocca, Piazza della Scienza, 2-20126 Milano, Italy.
Granata
Vincenzo
V
Del Vecchio
Pompea
P
Barone
Guido
G
Fusi
Paola
P
Tortora
Paolo
P
Graziano
Giuseppe
G
D019843:Archaeal Proteins; D002942:Circular Dichroism; D019641:DNA, Archaeal / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D005453:Fluorescence; D006358:Hot Temperature; D007930:Leucine / Q000737:chemistry*; D016944:Sulfolobus / Q000737:chemistry / Q000378:metabolism*
D019843:Archaeal Proteins; D019641:DNA, Archaeal; D004268:DNA-Binding Proteins; C093228:Sso7d protein, Sulfolobus; D007930:Leucine