Chaperones are a group of proteins that help in protein folding inside of the cell during normal physiological and stress conditions. The main function of chaperone protein is to prevent the aggregation of both newly synthesized polypeptide chains and protein subunits. Upon aggregation, a newly synthesized protein will form nonfunctional structures.
The main examples of chaperones are heat shock proteins (hsps) found in bacteria and archaea. The two main families of hsps are hsp70 (70-kDa heat shock protein) and hsp60 (60-kDa heat shock protein). The hsp70 binds to the short sequence of hydrophobic amino acids that appear after a new polypeptide chain is synthesized. On the other hand, the hsp60 (chaperonines) act later in the folding process and help hsp70 in protein folding.
In eukaryotes, the chaperons are found in the endoplasmic reticulum, the site of protein synthesis. Examples of eukaryotic chaperons are GRP78/BiP, GRP94, GRP170.