Comparative study of thermostability and structure of close homologs – barnase and binase

Parameters of heat denaturation and intrinsic fluorescence of barnase and its close homolog, binase in the pH region 2–6 have been determined. The barnase heat denaturation proceeds according to the “all-or-none” principle. Barnase denaturation temperature is lower than that of binase, enthalpy values of barnase and binase denaturation coinciding only at pH 4.5–5.5. Local environment of aromatic residues in the two proteins is similar. Secondary structures of ether the native or denaturated proteins are also not significantly different. Some differences in the barnase and binase electrostatic characteristics have been found. They are shown in the character of the dipole moments distribution in proteins.