[Ionic pairs in Bacillus intermedius 7P ribonuclease].

On the basis of X-ray determined coordinates specified with computer graphics and new data on amino acids sequence in the structure of Bacillus intermedius 7P ribonuclease there were analysed potentially charged residues and found ionic pairs binding independently denaturing regions-energetic domains. Five clusters of charged amino acids were found in the protein structure and several ionic bonds between the energetic domains were discovered: Asp7, Asp11-Arg109 and Lys26-Asp53,Glu72. Breaking of the latter makes their heat denaturation independent. Local surrounding of the ionic bonds is characterized and their role in the structure and cooperative properties of the globule is discussed.