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Effects of protein stability and structure on substrate processing by the ClpXP unfolding and degradation machine
Author(s) -
Burton Randall E.,
Siddiqui Samia M.,
Kim YongIn,
Baker Tania A.,
Sauer Robert T.
Publication year - 2001
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/20.12.3092
Subject(s) - biology , protein stability , degradation (telecommunications) , protein degradation , stability (learning theory) , protein structure , biophysics , biochemistry , computer science , telecommunications , machine learning
ClpXP is an ATP‐dependent protease that denatures native proteins and translocates the denatured polypeptide into an interior peptidase chamber for degradation. To address the mechanism of these processes, Arc repressor variants with dramatically different stabilities and unfolding half‐lives varying from months to seconds were targeted to ClpXP by addition of the ssrA degradation tag. Remarkably, ClpXP degraded each variant at a very similar rate and hydrolyzed ∼150 molecules of ATP for each molecule of substrate degraded. The hyperstable substrates did, however, slow the ClpXP ATPase cycle. These results confirm that ClpXP uses an active mechanism to denature its substrates, probably one that applies mechanical force to the native structure. Furthermore, the data suggest that denaturation is inherently inefficient or that significant levels of ATP hydrolysis are required for other reaction steps. ClpXP degraded disulfide‐cross‐linked dimers efficiently, even when just one subunit contained an ssrA tag. This result indicates that the pore through which denatured proteins enter the proteolytic chamber must be large enough to accommodate simultaneous passage of two or three polypeptide chains.