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 mitochondria and chloroplasts of eukaryotic cells. They are involved in protein folding, protein targeting to membranes, protein renaturation, and control of protein-protein interactions. They interact with many polypeptides in an ATP-dependent manner and possess a peptide-dependent ATPase activity. GroEL/hsp60 cooperates with GroES/hsp10, and the productive folding of proteins by GroEL generally requires GroES, which appears to regulate the binding and release of substrate proteins by GroEL. In a recent study, we have shown that GroEL interacts preferentially with the side chains of hydrophobic amino acids (Ile, Phe, Val, Leu, and Trp) and more weakly with several polar or charged amino acids, including the strongest alpha-helix and beta-sheet formers (Glu, Gln, His, Thr, and Tyr). In this study, we show that GroES reduces the specificity of GroEL for hydrophobic amino acids and increases its specificity for hydrophilic ones. This shift by GroES of the GroEL specificity from hydrophobic amino acids toward hydrophilic ones might be of importance for its function in protein folding.