Thermal stability of proteins does not correlate with the energy of intramolecular interactions

Abstract

Small monomeric proteins from mesophilic and thermophilic organisms were studied. They have close structural and physical and chemical properties but vary in thermal stability. A thermodynamic analysis of heat unfolding was made and integral enthalpy of unfolding (Δ H unf), heat capacity of hydration (Δ C p hyd) and enthalpy of hydration (Δ H hyd) and of the buried surface area (ΔASA) of nonpolar and polar groups as well as the enthalpy of disruption of intramolecular interaction (Δ H int in gas phase) at 298 K were determined. The absence of correlation between protein thermostability and energetic components suggests that regulatory mechanism of protein thermal stabilization has entropic nature.