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|a Nager, Andrew Ross
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|a Massachusetts Institute of Technology. Department of Biology
|e contributor
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|a Nager, Andrew Ross
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|a Baker, Tania
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|a Sauer, Robert T.
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|a Sauer, Robert T.
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|a Baker, Tania
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|a Stepwise Unfolding of a β Barrel Protein by the AAA+ ClpXP Protease
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|b Elsevier,
|c 2015-10-06T19:23:34Z.
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|z Get fulltext
|u http://hdl.handle.net/1721.1/99171
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|a In the AAA+ ClpXP protease, ClpX uses the energy of ATP binding and hydrolysis to unfold proteins before translocating them into ClpP for degradation. For proteins with C-terminal ssrA tags, ClpXP pulls on the tag to initiate unfolding and subsequent degradation. Here, we demonstrate that an initial step in ClpXP unfolding of the 11-stranded β barrel of superfolder GFP-ssrA involves extraction of the C-terminal β strand. The resulting 10-stranded intermediate is populated at low ATP concentrations, which stall ClpXP unfolding, and at high ATP concentrations, which support robust degradation. To determine if stable unfolding intermediates cause low-ATP stalling, we designed and characterized circularly permuted GFP variants. Notably, stalling was observed for a variant that formed a stable 10-stranded intermediate but not for one in which this intermediate was unstable. A stepwise degradation model in which the rates of terminal-strand extraction, strand refolding or recapture, and unfolding of the 10-stranded intermediate all depend on the rate of ATP hydrolysis by ClpXP accounts for the observed changes in degradation kinetics over a broad range of ATP concentrations. Our results suggest that the presence or absence of unfolding intermediates will play important roles in determining whether forced enzymatic unfolding requires a minimum rate of ATP hydrolysis.
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|a National Institutes of Health (U.S.) (Grant AI-15706)
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|a en_US
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|a Article
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|t Journal of Molecular Biology
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