An expanded conformation of single-ring GroEL-GroES complex encapsulates an 86 kDa substrate.
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.
Chen
Dong-Hua
DH
National Center for Macromolecular Imaging, Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030, USA.
Song
Jiu-Li
JL
Chuang
David T
DT
Chiu
Wah
W
Ludtke
Steven J
SJ
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
D018835:Chaperonin 10; D018834:Chaperonin 60; D000255:Adenosine Triphosphate; D007658:Ketone Oxidoreductases; D014357:Trypsin