title: Chaperonin-catalyzed rescue of kinetically trapped states in protein folding.
abstract: GroEL and GroES form a chaperonin nano-cage for single protein molecules to fold in isolation. The folding properties that render a protein chaperonin dependent are not yet understood. Here, we address this question using a double mutant of the maltose-binding protein DM-MBP as a substrate. Upon spontaneous refolding, DM-MBP populates a kinetically trapped intermediate that is collapsed but structurally disordered. Introducing two long-range disulfide bonds into DM-MBP reduces the entropic folding barrier of this intermediate and strongly accelerates native state formation. Strikingly, steric confinement of the protein in the chaperonin cage mimics the kinetic effect of constraining disulfides on folding, in a manner mediated by negative charge clusters in the cage wall. These findings suggest that chaperonin dependence correlates with the tendency of proteins to populate entropically stabilized folding intermediates. The capacity to rescue proteins from such folding traps may explain the uniquely essential role of chaperonin cages within the cellular chaperone network.
authors.affiliation: Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany.
authors.forename: Kausik
authors.initials: K
authors.lastname: Chakraborty
authors.forename: Manal
authors.initials: M
authors.lastname: Chatila
authors.forename: Jyoti
authors.initials: J
authors.lastname: Sinha
authors.forename: Qiaoyun
authors.initials: Q
authors.lastname: Shi
authors.forename: Bernhard C
authors.initials: BC
authors.lastname: Poschner
authors.forename: Martin
authors.initials: M
authors.lastname: Sikor
authors.forename: Guoxin
authors.initials: G
authors.lastname: Jiang
authors.forename: Don C
authors.initials: DC
authors.lastname: Lamb
authors.forename: F Ulrich
authors.initials: FU
authors.lastname: Hartl
authors.forename: Manajit
authors.initials: M
authors.lastname: Hayer-Hartl
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D018835:Chaperonin 10 / Q000378:metabolism*; D018834:Chaperonin 60 / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000378:metabolism*; D058619:Maltose-Binding Proteins; D008958:Models, Molecular; D033902:Periplasmic Binding Proteins / Q000378:metabolism; D017510:Protein Folding; D012247:Rhodospirillum rubrum / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D013816:Thermodynamics
chemical_list: D001426:Bacterial Proteins; D018835:Chaperonin 10; D018834:Chaperonin 60; D029968:Escherichia coli Proteins; D058619:Maltose-Binding Proteins; D033902:Periplasmic Binding Proteins