Subunit asymmetry and roles of conformational switching in the hexameric AAA+ ring of ClpX
Author(s)
Stinson, Benjamin Michael; Baytshtok, Vladimir; Schmitz, Karl Robert; Baker, Tania; Sauer, Robert T.
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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.
Date issued
2015-04Department
Massachusetts Institute of Technology. Department of Biology; Whitehead Institute for Biomedical ResearchJournal
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
ISSN
1545-9993
1545-9985