title: Visualizing GroEL/ES in the act of encapsulating a folding protein.
abstract: The GroEL/ES chaperonin system is required for the assisted folding of many proteins. How these substrate proteins are encapsulated within the GroEL-GroES cavity is poorly understood. Using symmetry-free, single-particle cryo-electron microscopy, we have characterized a chemically modified mutant of GroEL (EL43Py) that is trapped at a normally transient stage of substrate protein encapsulation. We show that the symmetric pattern of the GroEL subunits is broken as the GroEL cis-ring apical domains reorient to accommodate the simultaneous binding of GroES and an incompletely folded substrate protein (RuBisCO). The collapsed RuBisCO folding intermediate binds to the lower segment of two apical domains, as well as to the normally unstructured GroEL C-terminal tails. A comparative structural analysis suggests that the allosteric transitions leading to substrate protein release and folding involve concerted shifts of GroES and the GroEL apical domains and C-terminal tails.
authors.affiliation: Verna and Marrs McLean Department of Biochemistry and Molecular Biology, National Center for Macromolecular Imaging, Baylor College of Medicine, Houston, TX 77030, USA.
authors.forename: Dong-Hua
authors.initials: DH
authors.lastname: Chen
authors.forename: Damian
authors.initials: D
authors.lastname: Madan
authors.forename: Jeremy
authors.initials: J
authors.lastname: Weaver
authors.forename: Zong
authors.initials: Z
authors.lastname: Lin
authors.forename: Gunnar F
authors.initials: GF
authors.lastname: Schröder
authors.forename: Wah
authors.initials: W
authors.lastname: Chiu
authors.forename: Hays S
authors.initials: HS
authors.lastname: Rye
mesh_terms: D000244:Adenosine Diphosphate / Q000737:chemistry / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000737:chemistry / Q000378:metabolism; D018835:Chaperonin 10 / Q000378:metabolism*; D020285:Cryoelectron Microscopy; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D046912:Multiprotein Complexes / Q000737:chemistry / Q000378:metabolism; D011487:Protein Conformation; D017510:Protein Folding; D012273:Ribulose-Bisphosphate Carboxylase / Q000737:chemistry / Q000378:metabolism*
chemical_list: D018835:Chaperonin 10; D029968:Escherichia coli Proteins; C028715:GroE protein, E coli; D006360:Heat-Shock Proteins; D046912:Multiprotein Complexes; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D012273:Ribulose-Bisphosphate Carboxylase