title: GroEL and CCT are catalytic unfoldases mediating out-of-cage polypeptide refolding without ATP.
abstract: Chaperonins are cage-like complexes in which nonnative polypeptides prone to aggregation are thought to reach their native state optimally. However, they also may use ATP to unfold stably bound misfolded polypeptides and mediate the out-of-cage native refolding of large proteins. Here, we show that even without ATP and GroES, both GroEL and the eukaryotic chaperonin containing t-complex polypeptide 1 (CCT/TRiC) can unfold stable misfolded polypeptide conformers and readily release them from the access ways to the cage. Reconciling earlier disparate experimental observations to ours, we present a comprehensive model whereby following unfolding on the upper cavity, in-cage confinement is not needed for the released intermediates to slowly reach their native state in solution. As over-sticky intermediates occasionally stall the catalytic unfoldase sites, GroES mobile loops and ATP are necessary to dissociate the inhibitory species and regenerate the unfolding activity. Thus, chaperonin rings are not obligate confining antiaggregation cages. They are polypeptide unfoldases that can iteratively convert stable off-pathway conformers into functional proteins.
authors.affiliation: Department of Plant Molecular Biology, Faculty of Biology and Medicine, University of Lausanne, CH-1015 Lausanne, Switzerland.
authors.forename: Smriti
authors.initials: S
authors.lastname: Priya
authors.forename: Sandeep Kumar
authors.initials: SK
authors.lastname: Sharma
authors.forename: Vishal
authors.initials: V
authors.lastname: Sood
authors.forename: Rayees U H
authors.initials: RU
authors.lastname: Mattoo
authors.forename: Andrija
authors.initials: A
authors.lastname: Finka
authors.forename: Abdussalam
authors.initials: A
authors.lastname: Azem
authors.forename: Paolo
authors.initials: P
authors.lastname: De Los Rios
authors.forename: Pierre
authors.initials: P
authors.lastname: Goloubinoff
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D001059:Apoproteins / Q000378:metabolism; D055162:Biocatalysis / Q000187:drug effects*; D002417:Cattle; D018835:Chaperonin 10 / Q000378:metabolism; D018834:Chaperonin 60 / Q000378:metabolism*; D056404:Chaperonin Containing TCP-1 / Q000378:metabolism*; D005615:Freezing; D008958:Models, Molecular; D010455:Peptides / Q000378:metabolism*; D058849:Protein Refolding / Q000187:drug effects*; D020836:Protein Structure, Quaternary; D058767:Protein Unfolding / Q000187:drug effects*; D013379:Substrate Specificity / Q000187:drug effects; D034421:Sus scrofa; D013884:Thiosulfate Sulfurtransferase / Q000378:metabolism
chemical_list: D001059:Apoproteins; D018835:Chaperonin 10; D018834:Chaperonin 60; D010455:Peptides; D000255:Adenosine Triphosphate; D013884:Thiosulfate Sulfurtransferase; D056404:Chaperonin Containing TCP-1