Proteolysis and chaperones: the destruction/reconstruction dilemma.

Cytoplasmic proteases, although necessary for proper cell functioning, must be strictly regulated. In fact, they resemble chaperones, ancient protein folding devices. These molecules recognise exposed hydrophobic regions of unfolded or denatured proteins. For most substances it is not known how the cell chooses between the refolding and proteolytic pathways. In Escherichia coli, however, a carboxy-terminal proteolysis tag and binding site for the chaperone DnaK have recently been identified.