Structures of unliganded and ATP-bound states of the Escherichia coli chaperonin GroEL by cryoelectron microscopy

Alan M. Roseman, Neil A. Ranson, Brent Gowen, Stephen D. Fuller, Helen R. Saibil

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    We have developed an angular refinement procedure incorporating correction for the microscope contrast transfer function, to determine cryoelectron microscopy (cryo-EM) structures of the Escherichia coli chaperonin GroEL in its apo and ATP-bound forms. This image reconstruction procedure is verified to 13-Å resolution by comparison of the cryo-EM structure of unliganded GroEL with the crystal structure. Binding, encapsulation, and release of nonnative proteins by GroEL and its co-chaperone GroES are controlled by the binding and hydrolysis of ATP. Seven ATP molecules bind cooperatively to one heptameric ring of GroEL. This binding causes long-range conformational changes that determine the orientations of remote substrate-binding sites, and it also determines the conformation of subunits in the opposite ring of GroEL, in a negatively cooperative mechanism. The conformation of GroEL-ATP was determined at ∼15-Å resolution. In one ring of GroEL-ATP, the apical (substrate-binding) domains are extremely disordered, consistent with the high mobility needed for them to achieve the 60° elevation and 90° twist of the GroES-bound state. Unexpectedly, ATP binding also increases the separation between the two rings, although the interring contacts are present in the density map. © 2001 Academic Press.
    Original languageEnglish
    Pages (from-to)115-125
    Number of pages10
    JournalJournal of Structural Biology
    Issue number2
    Publication statusPublished - 2001


    • 3D reconstruction
    • ATP binding
    • Chaperonin
    • Cryoelectron microscopy
    • Molecular chaperone


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