Subunit asymmetry and roles of conformational switching in the hexameric AAA+ ring of ClpX
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Author(s)
Stinson, Benjamin Michael
Baytshtok, Vladimir
Schmitz, Karl Robert
Baker, Tania
Sauer, Robert T.
Date Issued
April 2015
Journal
Nature Structural & Molecular Biology
Publisher
Nature Publishing Group
Citation
Stinson, Benjamin M et al. “Subunit Asymmetry and Roles of Conformational Switching in the Hexameric AAA+ Ring of ClpX.” Nature Structural & Molecular Biology (2015): n. pag.
Version
Author's final manuscript
Abstract
The hexameric AAA+ ring of Escherichia coli ClpX, an ATP-dependent machine for protein unfolding and translocation, functions with the ClpP peptidase to degrade target substrates. For efficient function, ClpX subunits must switch between nucleotide-loadable (L) and nucleotide-unloadable (U) conformations, but the roles of switching are uncertain. Moreover, it is controversial whether working AAA+-ring enzymes assume symmetric or asymmetric conformations. Here, we show that a covalent ClpX ring with one subunit locked in the U conformation catalyzes robust ATP hydrolysis, with each unlocked subunit able to bind and hydrolyze ATP, albeit with highly asymmetric position-specific affinities. Preventing U↔L interconversion in one subunit alters the cooperativity of ATP hydrolysis and reduces the efficiency of substrate binding, unfolding and degradation, showing that conformational switching enhances multiple aspects of wild-type ClpX function. These results support an asymmetric and probabilistic model of AAA+-ring activity.
MIT Department
Massachusetts Institute of Technology. Department of Biology
Whitehead Institute for Biomedical Research
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Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
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DOI of Published Version
https://doi.org/10.1038/nsmb.3012
