Chaperone (protein)

Chaperone (protein)

In molecular biology, molecular chaperones are proteins that assist the non-covalent folding or unfolding and the assembly or disassembly of other macromolecular structures, but do not occur in these structures when the structures are performing their normal biological functions having completed the processes of folding and/or assembly. The common perception that chaperones are concerned primarily with protein folding is incorrect. The first protein to be called a chaperone assists the assembly of nucleosomes from folded histones and DNA and such assembly chaperones, especially in the nucleus, are concerned with the assembly of folded subunits into oligomeric structures.

One major function of chaperones is to prevent both newly synthesised polypeptide chains and assembled subunits from aggregating into nonfunctional structures. It is for this reason that many chaperones, but by no means all, are also heat shock proteins because the tendency to aggregate increases as proteins are denatured by stress. In this case, chaperones do not convey any additional steric information required for proteins to fold. However, some highly specific 'steric chaperones'do convey unique structural (steric) information onto proteins, which cannot be folded spontaneously. Such proteins violate Anfinsen's dogma.