NONPOLAR NUCLEI IN FUNGAL MICROBIAL RNASES

An application of a previously proposed method for the analysis of the non-polar structure of proteins is presented. A detailed analysis of the composition and properties of non-polar nuclei and microclusters o f fungal microbial ribonucleases has been performed on the basis of th e 3-D structures of RNase T1 and related proteins. Three hydrophobic n uclei were found in these structures. It has been shown that all resid ues in non-polar nuclei have high homology (similar to 89%). Residues in the nuclei are practically fully buried in the interior of a molecu le. Detailed analysis of non-polar nuclei properties shows that these nuclei determine the hydrophobic core of a protein and the location an d role of each residue in the non-polar interior of proteins. In addit ion it was found that there are variable residues not only on the surf ace of a protein but on the surface of the nuclei inside the protein a nd between the nuclei and that there is a consistent region in all pro teins, the hydrophobic gamma-nuclei. An evaluation of the stability of non-polar nuclei, the conservation of their compositions and their po sitions in the protein globule, allows one to assume that these three nuclei play an important functional role in the stability and folding of molecules of RNases and possibly can be considered as independent s tructural elements of 3-D structures of these proteins.