molecular chaperone

In biochemistry, a protein that protects other proteins from damage and unwanted interactions. Chaperones can also assist protein folding, the process in which a newly-synthesized polypeptide acquires its characteristic three-dimensional shape. As folding helpers, they are restricted to binding and releasing the substrate protein. They do not catalyse specific changes or impose certain structures.

The concept of molecular chaperones was developed in the 1980s when evidence emerged that many heat shock proteins can improve the yield of protein folding in the test tube by suppressing aggregation.

Research in the 1990s revealed that chaperones such as the heat shock protein GroEL protect their substrate proteins by repeated cycles of binding and release. A key reason why chaperones are needed in the cell (even though most proteins can fold unassisted in the test tube) is macromolecular crowding: that is the biomolecules are packed so densely that they are typically surrounded by other large molecules rather than by the solvent, water. This makes unwanted interactions more likely, and would lead to formation of insoluble aggregates if chaperones weren't present. A survey of substrate proteins revealed that larger proteins and those consisting of multiple subunits are particularly likely to require the supervision of chaperones.

The concept has also been expanded to cover RNA and metal ions. For example, there are proteins referred to as copper chaperones as they protect copper ions in the cell from involving in unwanted redox reactions.