Effect of polyglutamate on the thermal stability of ferricytochrome c.
The effect of saturated solutions of polyglutamate on the thermal stabilities of the Met-80-heme iron bond and of the ferricytochrome c as a whole were studied by absorption spectroscopy and differential scanning calorimetry at pH 7.0. According to spectral data the midtransition temperature of the cleavage of the sulfur-iron bond was 57.4 +/- 0.5 degrees C and 66.8 +/- 0.5 degrees C for cytochrome c and cytochrome c-polyglutamate complex, respectively. Addition of polyglutamate to cytochrome c at pH 7.0 alters the denaturation properties of the protein. As follows from DSC scans, the denaturation temperature for cytochrome c is decreased from 85.4 +/- 0.2 degrees C to 68.7 +/- 0.2 degrees C in the presence of the saturated amount of polyglutamate. The protein stability in terms of Gibbs energy change at protein unfolding amount to delta G(25 degrees C) = 22.7 +/- 2.7 and 32.0 +/- 2.2 kJ/mol, for cytochrome c and cytochrome c-polyglutamate complex, respectively, at pH 7.0. It is evident that polyglutamate increases the thermal stability of the sulfur-iron bond and decreases the denaturation temperature of the cytochrome c molecule as a whole. The complex thermal stability in terms of Gibbs energy is not lower than that of cytochrome c in the range of physiological temperatures.
Bágel'ová
J
J
Department of Biophysics, Slovak Academy of Sciences, Kosice, Slovakia.
Antalík
M
M
Tomori
Z
Z
D000818:Animals; D002152:Calorimetry, Differential Scanning; D003574:Cytochrome c Group / Q000737:chemistry* / Q000187:drug effects*; D004795:Enzyme Stability / Q000187:drug effects; D006736:Horses; D011099:Polyglutamic Acid / Q000494:pharmacology*; D011489:Protein Denaturation / Q000187:drug effects; D017510:Protein Folding; D012996:Solutions; D013053:Spectrophotometry; D013696:Temperature; D013816:Thermodynamics
D003574:Cytochrome c Group; D012996:Solutions; D011099:Polyglutamic Acid