Foldase

In molecular biology, foldases are a particular kind of molecular chaperones that assist the non-covalent folding of proteins in an ATP-dependent manner. Examples of foldase systems are the GroEL/GroES and the DnaK/DnaJ/GrpE system. In contrast to classical molecular chaperones that work as "holdases" and grip onto nascent protein chains to prevent aggregation or provide a hydrophobic environment for folding - as e.g. the GroEL/GroES system, foldases directly catalyze structural transitions in the polypeptide chain. They accelerate the rate-limiting steps along the folding pathway. Typical examples of foldases include Prolyl isomerase that catalyzes the transition between cis and trans isomers of Proline, disulfide oxidoreductase (DsbA) and disulfide isomerase (DsbC). The eukaryotic protein disulfide isomerases (PDI) catalyzes both protein cysteine oxidation and disulfide bond isomerization.