title: An expanded conformation of single-ring GroEL-GroES complex encapsulates an 86 kDa substrate.
abstract: Electron cryomicroscopy reveals an unprecedented conformation of the single-ring mutant of GroEL (SR398) bound to GroES in the presence of Mg-ATP. This conformation exhibits a considerable expansion of the folding cavity, with approximately 80% more volume than the X-ray structure of the equivalent cis cavity in the GroEL-GroES-(ADP)(7) complex. This expanded conformation can encapsulate an 86 kDa heterodimeric (alphabeta) assembly intermediate of mitochondrial branched-chain alpha-ketoacid dehydrogenase, the largest substrate ever observed to be cis encapsulated. The SR398-GroES-Mg-ATP complex is found to exist as a mixture of standard and expanded conformations, regardless of the absence or presence of the substrate. However, the presence of even a small substrate causes a pronounced bias toward the expanded conformation. Encapsulation of the large assembly intermediate is supported by a series of electron cryomicroscopy studies as well as the protection of both alpha and beta subunits of the substrate from tryptic digestion.
authors.affiliation: National Center for Macromolecular Imaging, Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030, USA.
authors.forename: Dong-Hua
authors.initials: DH
authors.lastname: Chen
authors.forename: Jiu-Li
authors.initials: JL
authors.lastname: Song
authors.forename: David T
authors.initials: DT
authors.lastname: Chuang
authors.forename: Wah
authors.initials: W
authors.lastname: Chiu
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Ludtke
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry; D018835:Chaperonin 10 / Q000737:chemistry*; D018834:Chaperonin 60 / Q000737:chemistry*; D020285:Cryoelectron Microscopy; D018360:Crystallography, X-Ray; D019281:Dimerization; D004926:Escherichia coli / Q000378:metabolism*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007658:Ketone Oxidoreductases / Q000737:chemistry; D008958:Models, Molecular; D008968:Molecular Conformation; D009154:Mutation; D011487:Protein Conformation; D014357:Trypsin / Q000737:chemistry
chemical_list: D018835:Chaperonin 10; D018834:Chaperonin 60; D000255:Adenosine Triphosphate; D007658:Ketone Oxidoreductases; D014357:Trypsin