REVERSAL BY GROES OF THE GROEL PREFERENCE FROM HYDROPHOBIC AMINO-ACIDS TOWARD HYDROPHILIC AMINO-ACIDS

The chaperones GroEL/hsp60 are present in all prokaryotes and in mitoc hondria and chloroplasts of eukaryotic cells. They are involved in pro tein folding, protein targeting to membranes, protein renaturation, an d control of protein protein interactions. They interact with many pol ypeptides in an ATP dependent manner and possess a peptide-dependent A TPase activity. GroEL/hsp60 cooperates with GroES/hsp10, and the produ ctive folding of proteins by GroEL generally requires GroES, which app ears to regulate the binding and release of substrate proteins by GroE L. In a recent study, we have shown that GroEL interacts preferentiall y with the side chains of hydrophobic amino acids (Ile, Phe, Val, Leu, and Trp) and more weakly with several polar or charged amino acids, i ncluding the strongest alpha-helix and beta-sheet formers (Glu, Gin, H is, Thr, and Tyr). In this study, we show that GroES reduces the speci ficity of GroEL for hydrophobic amino acids and increases its specific ity for hydrophilic ones. This shift by GroES of the GroEL specificity from hydrophobic amino acids toward hydrophilic ones might be of impo rtance for its function in protein folding.