GroEL is a protein chaperone required for the proper folding of many proteins in prokaryotes. To function properly, it requires the cochaperone protein GroES. (GroEL and GroES are also sometimes referred to as chaperonin and cochaperonin, or chaperonin 60 and chaperonin 10 for their molecular weights.) In eukaryotes the proteins Hsp60 and Hsp10 are structurally and functionally nearly identical to GroEL and GroES, respectively.

A class of chaperones, characterized by GroEL/GroES act in this way. The GroEL/GroES complex traps a string of exposed and unfolded amino acids in its bottle-like enclosure. At this initial stage, the interior of the chaperone complex is highly hydrophobic. Once the protein (or one domain of a larger protein) is properly folded within this capsule, the interior changes to a hydrophilic environment. This releases the folded domain to the aqueous environment outside of the chaperone; the cycle can then repeat. The cycling between hydrophilic and hydrophobic interiors requires a conformational change in the GroEL/GroES structure, and is driven by ATP hydrolysis.