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Updated: Jul 15, 2026

Detection of the pH-dependent Activity of Escherichia coli Chaperone HdeB In Vitro and In Vivo
Published on: October 23, 2016
Two families of chaperonin: physiology and mechanism
Arthur L Horwich1, Wayne A Fenton, Eli Chapman
1Department of Genetics, Yale University School of Medicine, New Haven, CT 06510, USA. arthur.horwich@yale.edu
Abstract:
Chaperonins are large ring assemblies that assist protein folding to the native state by binding nonnative proteins in their central cavities and then, upon binding ATP, release the substrate protein into a now-encapsulated cavity to fold productively. Two families of such components have been identified: type I in mitochondria, chloroplasts, and the bacterial cytosol, which rely on a detachable "lid" structure for encapsulation, and type II in archaea and the eukaryotic cytosol, which contain a built-in protrusion structure. We discuss here a number of issues under current study. What is the range of substrates acted on by the two classes of chaperonin, in particular by GroEL in the bacterial cytoplasm and CCT in the eukaryotic cytosol, and are all these substrates subject to encapsulation? What are the determinants for substrate binding by the type II chaperonins? And is the encapsulated chaperonin cavity a passive container that prevents aggregation, or could it be playing an active role in polypeptide folding?
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