MecA, an adaptor protein necessary for ClpC chaperone activity

Schlothauer, Tilman; Mogk, Axel; Dougan, David A.; Bukau, Bernd; Turgay, Kürşad

doi:10.1073/pnas.0535717100

Cited by 147 publications

(188 citation statements)

References 44 publications

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“…Unlike renatured B. subtilis YjbH (BsYjbH), GtYjbH is highly active, mediating rapid substrate degradation in reactions containing approximately 30-fold less GtYjbH than ClpXP or Spx in terms of molar equivalents. Unlike other well-studied adaptors (Dougan et al, 2002;Levchenko et al, 2000;Persuh et al, 2002;Schlothauer et al, 2003), no evidence of YjbH-ClpX interaction was detected. However, like the adaptor SspB (Levchenko et al, 2005), YjbH requires recognition of the C-terminal residues of Spx to enhance ClpXP-catalysed proteolysis.…”

Section: Introductioncontrasting

confidence: 63%

Geobacillus thermodenitrificans YjbH recognizes the C-terminal end of Bacillus subtilis Spx to accelerate Spx proteolysis by ClpXP

et al. 2012

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Proteolytic control can govern the levels of specific regulatory factors, such as Spx, a transcriptional regulator of the oxidative stress response in Gram-positive bacteria. Under oxidative stress, Spx concentration is elevated and upregulates transcription of genes that function in the stress response. When stress is alleviated, proteolysis of Spx catalysed by ClpXP reduces Spx concentration. Proteolysis is enhanced by the substrate recognition factor YjbH, which possesses a His-Cys-rich region at its N terminus. However, mutations that generate H12A, C13A, H14A, H16A and C31/34A residue substitutions in the N terminus of Bacillus subtilis YjbH (BsYjbH) do not affect functionality in Spx proteolytic control in vivo and in vitro. Because of difficulties in obtaining soluble BsYjbH, the Geobacillus thermodenitrificans yjbH gene was cloned, which yielded soluble GtYjbH protein. Despite its lack of a His-Cys-rich region, GtYjbH complements a B. subtilis yjbH null mutant, and shows high activity in vitro when combined with ClpXP and Spx in an approximately 30 : 1 (ClpXP/Spx : GtYjbH) molar ratio. In vitro interaction experiments showed that Spx and the protease-resistant Spx DD (in which the last two residues of Spx are replaced with two Asp residues) bind to GtYjbH, but deletion of 12 residues from the Spx C terminus (SpxDC) significantly diminished interaction and proteolytic degradation, indicating that the C terminus of Spx is important for YjbH recognition. These experiments also showed that Spx, but not GtYjbH, interacts with ClpX. Kinetic measurements for Spx proteolysis by ClpXP in the presence and absence of GtYjbH suggest that YjbH overcomes non-productive Spx-ClpX interaction, resulting in rapid degradation.

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Section: Introductioncontrasting

confidence: 63%

Geobacillus thermodenitrificans YjbH recognizes the C-terminal end of Bacillus subtilis Spx to accelerate Spx proteolysis by ClpXP

et al. 2012

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“…MecA consists of two domains. The N-terminal domain is responsible for recognition and targeting of substrates (60,68), and the C-terminal domain is necessary for the interaction with ClpC (61). In a similar manner, NblA binds via its C-terminal helix to the ␣-subunits of phycobiliproteins, which are probably substrates of ClpC, and via its N-terminal helix to ClpC (see Figs.…”

Section: Discussionmentioning

confidence: 99%

NblA, a Key Protein of Phycobilisome Degradation, Interacts with ClpC, a HSP100 Chaperone Partner of a Cyanobacterial Clp Protease

Karradt

Sobanski

Mattow

et al. 2008

Journal of Biological Chemistry

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When cyanobacteria are starved for nitrogen, expression of the NblA protein increases and thereby induces proteolytic degradation of phycobilisomes, light-harvesting complexes of pigmented proteins. Phycobilisome degradation leads to a color change of the cells from blue-green to yellow-green, referred to as bleaching or chlorosis. As reported previously, NblA binds via a conserved region at its C terminus to the ␣-subunits of phycobiliproteins, the main components of phycobilisomes. We demonstrate here that a highly conserved stretch of amino acids in the N-terminal helix of NblA is essential for protein function in vivo. Affinity purification of glutathione S-transferase-tagged NblA, expressed in a Nostoc sp. PCC7120 mutant lacking wildtype NblA, resulted in co-precipitation of ClpC, encoded by open reading frame alr2999 of the Nostoc chromosome. ClpC is a HSP100 chaperone partner of the Clp protease. ATP-dependent binding of NblA to ClpC was corroborated by in vitro pulldown assays. Introducing amino acid exchanges, we verified that the conserved N-terminal motif of NblA mediates the interaction with ClpC. Further results indicate that NblA binds phycobiliprotein subunits and ClpC simultaneously, thus bringing the proteins into close proximity. Altogether these results suggest that NblA may act as an adaptor protein that guides a ClpC⅐ClpP complex to the phycobiliprotein disks in the rods of phycobilisomes, thereby initiating the degradation process.

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“…In Bacillus subtilis, the MecA protein acts as an adaptor protein that facilitates the degradation of the transcriptional master regulator of competence ComK and the small quorum sensing-regulated competence protein ComS (30). More recently, MecA has also been shown to mediate the ClpC-dependent disaggregation, refolding, and degrading of ClpP substrates (31). Although it is true that MecA can be degraded by ClpCP both in vitro and in vivo, this degradation occurs in an ATP-dependent manner with in vitro kinetics that are much slower than the degradation rate of the substrate (30,31).…”

Section: Discussionmentioning

confidence: 99%

“…More recently, MecA has also been shown to mediate the ClpC-dependent disaggregation, refolding, and degrading of ClpP substrates (31). Although it is true that MecA can be degraded by ClpCP both in vitro and in vivo, this degradation occurs in an ATP-dependent manner with in vitro kinetics that are much slower than the degradation rate of the substrate (30,31). Moreover, the latter study points out that in the presence of an appropriate substrate such as aggregated malate dehydrogenase, MecA degradation was reduced (31).…”

Section: Discussionmentioning

confidence: 99%

The extracytoplasmic adaptor protein CpxP is degraded with substrate by DegP

Isaac

Pinkner²,

Hultgren³

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

148

175

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In Escherichia coli, the CpxR͞A two-component system senses various types of extracytoplasmic stresses and responds by activating the expression of genes encoding periplasmic protein folding and trafficking factors that clear such stresses to ensure the organism's survival. The cpxP gene encodes a small, stresscombative periplasmic protein and is the most strongly induced member of the Cpx regulon. We demonstrate that the Cpx stress response suppresses the toxicity associated with two misfolded proteins derived from the P pilus of uropathogenic E. coli and that mutations in either cpxP or the gene for the periplasmic protease DegP prevent suppression by preventing the degradation of these proteins. Strikingly, the presence of a periplasmic misfolded protein substrate significantly enhances the proteolysis of CpxP by DegP. Our data suggest that CpxP functions as a periplasmic adaptor protein that is required for the effective proteolysis of a subset of misfolded substrates by the DegP protease.Escherichia coli ͉ misfolded protein ͉ periplasm ͉ regulated proteolysis

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MecA, an adaptor protein necessary for ClpC chaperone activity

Abstract: ClpC of

Cited by 147 publications

References 44 publications

Geobacillus thermodenitrificans YjbH recognizes the C-terminal end of Bacillus subtilis Spx to accelerate Spx proteolysis by ClpXP

Geobacillus thermodenitrificans YjbH recognizes the C-terminal end of Bacillus subtilis Spx to accelerate Spx proteolysis by ClpXP

NblA, a Key Protein of Phycobilisome Degradation, Interacts with ClpC, a HSP100 Chaperone Partner of a Cyanobacterial Clp Protease

The extracytoplasmic adaptor protein CpxP is degraded with substrate by DegP

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