title: Cryo-EM structure of a group II chaperonin in the prehydrolysis ATP-bound state leading to lid closure.
abstract: Chaperonins are large ATP-driven molecular machines that mediate cellular protein folding. Group II chaperonins use their "built-in lid" to close their central folding chamber. Here we report the structure of an archaeal group II chaperonin in its prehydrolysis ATP-bound state at subnanometer resolution using single particle cryo-electron microscopy (cryo-EM). Structural comparison of Mm-cpn in ATP-free, ATP-bound, and ATP-hydrolysis states reveals that ATP binding alone causes the chaperonin to close slightly with a ∼45° counterclockwise rotation of the apical domain. The subsequent ATP hydrolysis drives each subunit to rock toward the folding chamber and to close the lid completely. These motions are attributable to the local interactions of specific active site residues with the nucleotide, the tight couplings between the apical and intermediate domains within the subunit, and the aligned interactions between two subunits across the rings. This mechanism of structural changes in response to ATP is entirely different from those found in group I chaperonins.
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: Junjie
authors.initials: J
authors.lastname: Zhang
authors.forename: Boxue
authors.initials: B
authors.lastname: Ma
authors.forename: Frank
authors.initials: F
authors.lastname: DiMaio
authors.forename: Nicholai R
authors.initials: NR
authors.lastname: Douglas
authors.forename: Lukasz A
authors.initials: LA
authors.lastname: Joachimiak
authors.forename: David
authors.initials: D
authors.lastname: Baker
authors.forename: Judith
authors.initials: J
authors.lastname: Frydman
authors.forename: Michael
authors.initials: M
authors.lastname: Levitt
authors.forename: Wah
authors.initials: W
authors.lastname: Chiu
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D001665:Binding Sites; D020285:Cryoelectron Microscopy / Q000379:methods; D056385:Group II Chaperonins / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D006868:Hydrolysis; D017017:Methanococcus / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D011485:Protein Binding; D011487:Protein Conformation; D017510:Protein Folding; D021122:Protein Subunits / Q000737:chemistry* / Q000378:metabolism
chemical_list: D021122:Protein Subunits; D000255:Adenosine Triphosphate; D056385:Group II Chaperonins