HSP70 a critical chaperone protein that has a high affinity for unfolded polypeptide chains. It binds extended peptide segments with a net hydrophobic character exposed by polypeptides during translation and membrane translocation, or following stress-induced damage. In cooperation with other chaperones, Hsp70 stabilizes preexistent proteins against aggregation and mediates the folding of newly translated polypeptides in the cytosol as well as within organelles. Hsp70 and Hsp40 recruit some misfolded proteins to the ubiquitin E3 ligase CHIP for ubiquitination.