Specificity of spatial clustering of amino acid residues as an evolutionary trend in proteins

Three-dimensional structures of cytochrome c and myoglobin molecules together with amino acid substitution data on these proteins from a close range of taxa highlight an interesting evolutionary trend. Assuming three-dimensional structures of homologous proteins to be largely similar, the distribution of amino acid residue types around one another was studied. The application of information theory to three dimensional arrangement of amino acid residues revealed that in general, the higher the taxonomic order, the more specific is the clustering of residue types with one another.