title: GroEL/GroES-mediated folding of a protein too large to be encapsulated.
abstract: The chaperonin GroEL binds nonnative proteins too large to fit inside the productive GroEL-GroES cis cavity, but whether and how it assists their folding has remained unanswered. We have examined yeast mitochondrial aconitase, an 82 kDa monomeric Fe(4)S(4) cluster-containing enzyme, observed to aggregate in chaperonin-deficient mitochondria. We observed that aconitase folding both in vivo and in vitro requires both GroEL and GroES, and proceeds via multiple rounds of binding and release. Unlike the folding of smaller substrates, however, this mechanism does not involve cis encapsulation but, rather, requires GroES binding to the trans ring to release nonnative substrate, which likely folds in solution. Following the phase of ATP/GroES-dependent refolding, GroEL stably bound apoaconitase, releasing active holoenzyme upon Fe(4)S(4) cofactor formation, independent of ATP and GroES.
authors.affiliation: Howard Hughes Medical Institute, Department of Genetics, Yale University School of Medicine, Boyer Center, New Haven, CT 06510, USA.
authors.forename: T K
authors.initials: TK
authors.lastname: Chaudhuri
authors.forename: G W
authors.initials: GW
authors.lastname: Farr
authors.forename: W A
authors.initials: WA
authors.lastname: Fenton
authors.forename: S
authors.initials: S
authors.lastname: Rospert
authors.forename: A L
authors.initials: AL
authors.lastname: Horwich
mesh_terms: D000154:Aconitate Hydratase / Q000737:chemistry; D000255:Adenosine Triphosphate / Q000378:metabolism; D019921:Biotinylation; D018835:Chaperonin 10 / Q000737:chemistry*; D018834:Chaperonin 60 / Q000737:chemistry*; D004591:Electrophoresis, Polyacrylamide Gel; D019286:Endopeptidase K / Q000378:metabolism; D004926:Escherichia coli / Q000737:chemistry; D005656:Fungal Proteins / Q000737:chemistry; D008954:Models, Biological; D011485:Protein Binding; D017510:Protein Folding; D013997:Time Factors
chemical_list: D018835:Chaperonin 10; D018834:Chaperonin 60; D005656:Fungal Proteins; D000255:Adenosine Triphosphate; D019286:Endopeptidase K; D000154:Aconitate Hydratase