The structure of ClpB: a molecular chaperone that rescues proteins from an aggregated state

Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA.
Cell (Impact Factor: 33.12). 10/2003; 115(2):229-40.
Source: PubMed

ABSTRACT Molecular chaperones assist protein folding by facilitating their "forward" folding and preventing aggregation. However, once aggregates have formed, these chaperones cannot facilitate protein disaggregation. Bacterial ClpB and its eukaryotic homolog Hsp104 are essential proteins of the heat-shock response, which have the remarkable capacity to rescue stress-damaged proteins from an aggregated state. We have determined the structure of Thermus thermophilus ClpB (TClpB) using a combination of X-ray crystallography and cryo-electron microscopy (cryo-EM). Our single-particle reconstruction shows that TClpB forms a two-tiered hexameric ring. The ClpB/Hsp104-linker consists of an 85 A long and mobile coiled coil that is located on the outside of the hexamer. Our mutagenesis and biochemical data show that both the relative position and motion of this coiled coil are critical for chaperone function. Taken together, we propose a mechanism by which an ATP-driven conformational change is coupled to a large coiled-coil motion, which is indispensable for protein disaggregation.

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    • "The bacterial ClpB monomer contains an N-terminal domain and two AAA+ nucleotide-binding domains (NBD) separated by a coiled-coil middle-domain (M-domain) (Barnett et al. 2000; DeSantis and Shorter 2012; Doyle and Wickner 2009). Several studies indicate that the M-domain is essential for the chaperone activity (Barnett et al. 2005; Kedzierska et al. 2003; Lee et al. 2005; Mogk et al. 2003; Schirmer et al. 2004). Protein disaggregation by ClpB in vitro requires the collaboration of a second ATP-dependent molecular chaperone, DnaK, to promote the solubilization and reactivation of proteins that misfold and aggregate following heat shock (Goloubinoff et al. 1999; Motohashi et al. 1999; Zolkiewski 1999). "
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    • "We used the homology modeling approach, implemented in the MODELLER [Sali and Blundell, 1993] 9v10 program, to build models of torsinAwt, delE302, delE303, F205I and R288Q based on the 3D structure of the ClpB second AAA+ domain of Thermus thermophilus (T. thermophilus) [Lee et al., 2003]. The protocol used to perform the molecular modeling experiments was: generation of 10 models, from which one model for each torsinA sequence was selected. "
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    ABSTRACT: Early-onset dystonia is associated with the deletion of one of a pair of glutamic acid residues (c.904_906delGAG/c.907_909delGAG; p.Glu302del/Glu303del; ΔE 302/303) near the carboxyl-terminus of torsinA, a member of the AAA+ protein family that localizes to the endoplasmic reticulum (ER) lumen and nuclear envelope (NE). This deletion commonly underlies early-onset DYT1 dystonia. While the role of the disease-causing mutation, torsinAΔE, has been established through genetic association studies, it is much less clear whether other rare human variants of torsinA are pathogenic. Two missense variations have been described in single patients; R288Q (c.863G>A; p.Arg288Gln; R288Q) identified in a patient with onset of severe generalized dystonia and myoclonus since infancy, and F205I (c.613T>A, p.Phe205Ile; F205I) in a psychiatric patient with late-onset focal dystonia. In this study, we have undertaken a series of analyses comparing the biochemical and cellular effects of these rare variants to torsinAΔE and wild-type (wt) torsinA in order to reveal whether there are common dysfunctional features. The results revealed that the variants, R288Q and F205I, are more similar in their properties to torsinAΔE protein than to torsinAwt. These findings provide functional evidence for the potential pathogenic nature of these rare sequence variants in the TOR1A gene, thus implicating these pathologies in the development of dystonia. This article is protected by copyright. All rights reserved.
    Human Mutation 09/2014; DOI:10.1002/humu.22602 · 5.05 Impact Factor
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    • "It has been demonstrated that MD is a mobile element of ClpB. Its position and degree of mobility significantly affect this protein's chaperone activity and in turn the protein disaggregation and reactivation processes [11]. "
    Advances in Bioscience and Biotechnology 01/2014; 5(01):31-35. DOI:10.4236/abb.2014.51005
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