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 .
Structurally, GroEL is a dual-ringed tetradecamer, with both the cis and trans rings consisting of seven subunits each. The inside of GroEL is hydrophobic, and is likely where protein folding takes place.
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