chaperonische

Chaperonins are a class of molecular chaperones that assist in the proper folding and assembly of proteins within cells. Unlike other chaperones, such as heat shock proteins (Hsp70), chaperonins form large, barrel-like structures that create a protected environment for protein folding. These structures are typically composed of multiple subunits arranged in a cylindrical shape, resembling a two-stack barrel.

Chaperonins are found in all three domains of life—bacteria, archaea, and eukaryotes—though their specific forms vary. The most well-studied chaperonins include the GroEL-GroES system in bacteria and the TRiC (TCP-1 ring complex) in eukaryotes. GroEL, a 14-mer composed of two stacked heptameric rings, works in conjunction with GroES, a heptameric cap that binds to one end of the GroEL barrel. This complex facilitates the folding of unfolded or misfolded proteins by sequestering them inside the chamber and providing an isolated, ATP-dependent environment for proper refolding.

The mechanism of chaperonin function involves several key steps: substrate binding, ATP hydrolysis, lid binding, and product release. Unfolded proteins bind to the GroEL barrel, triggering ATP hydrolysis and conformational changes that expose hydrophobic binding sites. The GroES lid then binds to one end of the GroEL barrel, encapsulating the substrate and promoting folding. ATP binding and hydrolysis cycles drive the release of the properly folded protein or misfolded substrates for another round of folding attempts.

Chaperonins play a critical role in maintaining cellular proteostasis, particularly under stress conditions such as heat shock or oxidative damage. Their ability to prevent protein aggregation and facilitate correct protein folding is essential for cellular function and survival. Deficiencies in chaperonin function have been linked to various diseases, including neurodegenerative disorders and metabolic syndromes, highlighting their importance in both basic cellular processes and human health.