GroES (chaperonin 10) is an oligomeric molecular chaperone, which functions in protein folding and possibly in intercellular signalling, being found on the surface of various prokaryotic and eukaryotic cells, as well as being released from cells. Secreted chaperonins are thought to act as intercellular signals, interacting with a variety of cell types, including leukocytes, vascular endothelial cells and epithelial cells, as well as activating key cellular activities such as the synthesis of cytokines and adhesion proteins . GroES works as a co-chaperone with GroEL (chaperonin 60) during protein folding. The polypeptide substrate is captured by GroEL, which bind the co-chaperone GroES and ATP, and discharges the substrate into a unique microenvironment inside of the chaperone, which promotes productive folding. After hydrolysis of ATP, the polypeptide is released into solution . GP31 from Bacteriophage T4 is functionally equivalent to GroES. GroES folds as a partly opened beta-barrel.
The N-terminal domain of alcohol dehydrogenase-like proteins have a GroES-like fold, the C-terminal domain having a classical Rossman-fold . These proteins include, alcohol dehydrogenase, which contains a zinc-finger subdomain within the GroES-like domain, ketose reductase (sorbitol dehydrogenase), formaldehyde dehydrogenase, quinone oxidoreductase and 2,4-dienoyl-CoA reductase.