Beschreibung:
AbstractThe 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 °C and 66.8±0.5 °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 °C to 68.7±0.2 °C in the presence of the saturated amount of polyglutamate. The protein stability in terms of Gibbs energy change at protein unfolding amount to ΔG(25°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.