Amino acid specificity of the Escherichia coli chaperone GroEL (heat shock protein 60).

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. The nature of the structural elements of substrate proteins recognized by GroEL/hsp60 is still unknown. In this study, we show that the GroEL chaperone of Escherichia coli interacts with single amino acids. The hydrophobic amino acids Ile, Phe, Val, Leu, and Trp present the strongest interaction with GroEL. While most of these hydrophobic amino acids are beta-sheet formers, GroEL interacts also with the alpha-helix formers Glu, Ala, Gln, and His. The multiple interactions of GroEL with the side chains of hydrophobic and polar amino acids, including the strongest alpha-helix and beta-sheet formers would allow this chaperone to act as an amphiphilic organizer of protein folding.