Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A bacterially expressed recombinant HClpP protein, the human homologue of Escherichia coli ClpP protease, was used to obtain specific polyclonal antibodies. Those antibodies identify a 26 kDa polypeptide in mitochondrial subcellular fractions of rat and human liver. Immunofluorescence and electron microscopic studies demonstrate that the mammalian homologue of ClpP is located in the mitochondrial matrix with a tendency to be found in association with the inner mitochondrial membrane. An HClpP recombinant protein with a truncated NH2terminus (missing the first 58 amino acid residues) shows a molecular mass of 26 kDa under denaturing conditions. This N-truncated HClpP recombinant protein shows a native molecular mass of 340 kDa that is identical with the native molecular mass of the partially purified protein from rat liver mitochondria. Electron microscopy shows that the N-truncated recombinant HClpP has a ring shape with seven identical morphological units in the periphery, exhibiting a 7-fold symmetry. The native molecular mass and the electron microscopic studies suggest that mitochondrial ClpP is composed of two heptameric rings with 7-fold symmetry, similar to E. coli ClpP.
J Mol Biol 1999 Oct 01
PMID:Mitochondrial localization and oligomeric structure of HClpP, the human homologue of E. coli ClpP. 1052 7

sigmaS (RpoS) is the master regulator of the general stress response in Escherichia coli. Several stresses increase cellular sigmaS levels by inhibiting proteolysis of sigmaS, which under non-stress conditions is a highly unstable protein. For this ClpXP-dependent degradation, the response regulator RssB acts as a recognition factor, with RssB affinity for sigmaS being modulated by phosphorylation. Here, we demonstrate that RssB can also act like an anti-sigma factor for sigmaS in vivo, i.e. RssB can inhibit the expression of sigmaS-dependent genes in the presence of high sigmaS levels. This becomes apparent when (i) the cellular RssB/sigmaS ratio is at least somewhat elevated and (ii) proteolysis is reduced (for example in stationary phase) or eliminated (for example in a clpP mutant). Two modes of inhibition of sigmaS by RssB can be distinguished. The 'catalytic' mode is observed in stationary phase cells with a substoichiometric RssB/sigmaS ratio, requires ClpP and therefore probably corresponds to sequestering of sigmaS to Clp protease (even though sigmaS is not degraded). The 'stoichiometric' mode occurs in clpP mutant cells upon overproduction of RssB to levels that are equal to those of sigmaS, and therefore probably involves binary complex formation between RssB and sigmaS. We also show that, under standard laboratory conditions, the cellular level of RssB is more than 20-fold lower than that of sigmaS and is not significantly controlled by stresses that upregulate sigmaS. We therefore propose that antisigma factor activity of RssB may play a role under not yet identified growth conditions (which may result in RssB induction), or that RssB is a former antisigma factor that during evolution was recruited to serve as a recognition factor for proteolysis.
Mol Microbiol 2000 Feb
PMID:The response regulator RssB, a recognition factor for sigmaS proteolysis in Escherichia coli, can act like an anti-sigmaS factor. 1067 87

Stress proteins play an important role in virulence, yet little is known about the regulation of stress response in pathogens. In the facultative intracellular pathogen Listeria monocytogenes, the Clp ATPases, including ClpC, ClpP and ClpE, are required for stress survival and intracellular growth. The first gene of the clpC operon of L. monocytogenes encodes a homologue of the Bacillus subtilis CtsR repressor of stress response genes. An L. monocytogenes ctsR-deleted mutant displayed enhanced survival under stress conditions (growth in the presence of 2% NaCl or at 42 degrees C), but its level of virulence in the mouse was not affected. The virulence of a wild-type strain constitutively expressing CtsR is significantly attenuated, presumably because of repression of the stress response. Regulation of the L. monocytogenes clpC, clpP and clpE genes was investigated using transcriptional fusions in B. subtilis as a host. The L. monocytogenes ctsR gene was placed under the control of an inducible promoter, and regulation by CtsR and heat shock was demonstrated in vivo in B. subtilis. The purified CtsR protein of L. monocytogenes binds specifically to the clpC, clpP and clpE regulatory regions, and the extent of the CtsR binding sites was defined by DNase I footprinting. Our results demonstrate that this human pathogen possesses a CtsR regulon controlling class III heat shock genes, strikingly similar to that of the saprophyte B. subtilis. This is the first description of a stress response regulatory gene in a pathogen.
Mol Microbiol 2000 Feb
PMID:CtsR controls class III heat shock gene expression in the human pathogen Listeria monocytogenes. 1069 57

We used mini Tn10 transposition to generate a library of Bacillus subtilis insertion mutants, with the goal of identifying and characterizing new competence genes. Two new regulatory genes were identified in our screen: ypuN (also known as rsiX, the anti-sigmaX factor) and ylbF. The disruption of ylbF leads to a dramatic decrease in the expression of comK, encoding the competence transcription factor. Our data show that ylbF positively controls ComK at a post-transcriptional level. It has been reported previously that ComK is degraded in vivo and in vitro by a multimeric protein complex composed of ClpP, ClpC and MecA. This proteolysis is inhibited by the ComS peptide. We show that both the overexpression of comS and the inactivation of mecA individually suffice to bypass the competence phenotype of the ylbF mutation. This mutation does not seem to alter the cellular concentrations of MecA or ClpP, and we propose a role for YlbF in modulating the translation, stability or activity of ComS. In addition to its role in competence, ylbF also appears to regulate sporulation by acting before stage II.
Mol Microbiol 2000 Mar
PMID:Characterization of ylbF, a new gene involved in competence development and sporulation in Bacillus subtilis. 1071 92

We identified the stress-induced ClpP of Listeria monocytogenes and demonstrated its crucial role in intracellular survival of this pathogen. ClpP is a 21.6 kDa protein belonging to a family of proteases highly conserved in prokaryotes and eukaryotes. A clpP-deleted mutant enabled us to demonstrate that ClpP is involved in proteolysis and is required for growth under stress conditions. Intramacrophage survival of this mutant was strongly restricted, thus resulting in loss of virulence for the mouse. The activity of listeriolysin O, a major virulence factor implicated in bacterial escape from phagosomes of macrophages, was much reduced in the clpP mutant under stress conditions. Direct evidence for the role of ClpP in the intracellular parasitism was obtained by showing that virulence and haemolytic activity were fully restored by complementation of the mutant. These results suggest that ClpP is involved in the rapid adaptive response of intracellular pathogens during the infectious process.
Mol Microbiol 2000 Mar
PMID:The ClpP serine protease is essential for the intracellular parasitism and virulence of Listeria monocytogenes. 1076 Jan 31

ClpXP is a protein machine composed of the ClpX ATPase, a member of the Clp/Hsp100 family of remodeling enzymes, and the ClpP peptidase. Here, ClpX and ClpXP are shown to catalyze denaturation of GFP modified with an ssrA degradation tag. ClpX translocates this denatured protein into the proteolytic chamber of ClpP and, when proteolysis is blocked, also catalyzes release of denatured GFP-ssrA from ClpP in a reaction that requires ATP and additional substrate. Kinetic experiments reveal that multiple reaction steps require collaboration between ClpX and ClpP and that denaturation is the rate-determining step in degradation. These insights into the mechanism of ClpXP explain how it executes efficient degradation in a manner that is highly specific for tagged proteins, irrespective of their intrinsic stabilities.
Mol Cell 2000 Apr
PMID:Dynamics of substrate denaturation and translocation by the ClpXP degradation machine. 1088

The alternate sigma factor sigmaS plays an important role in the survival of Salmonella typhimurium following sudden encounters with a variety of stress conditions. The level of sigmaS is very low in rapidly growing cells but dramatically increases as those cells encounter environmental stress or enter into stationary phase. This increase is due in large measure to the stabilization of sigmaS protein against degradation by the ClpXP protease. The MviA protein, also known as RssB or SprE in Escherichia coli, is a putative member of a two component signal transduction system that plays a central role in facilitating sigmaS degradation by ClpXP. In contrast to most two-component systems, MviA does not appear to regulate gene expression but is believed to interact directly with sigmaS and somehow facilitate degradation. We now provide evidence that MviA(RssB) directly interacts both with sigmaS and ClpX in vivo, presumably enabling presentation of sigmaS to the ClpP protease. Interactions were demonstrated using a bacterial two-hybrid system in which sigmaS, MviA, and ClpX were fused to separate moieties of Bordetella pertussis CyaA (adenylate cyclase). Paired hybrid plasmids containing Cya'-MviA/RpoS-'Cya or Cya'-MviA/ClpX-'Cya successfully reconstituted adenylate cyclase activity in both S. typhimurium and E. coli. However, no direct interactions were detected between ClpX and RpoS. A second series of experiments has indicated that the interaction between MviA and sigmaS requires the N-terminus but not the C-terminus of MviA. Cellular levels of MviA appear to be very low in the cell based on lacZ fusion, Western blot and Northern blot analyses suggesting a catalytic role for MviA in sigmaS degradation. Mutagenesis of MviA residue D58, a canonical residue subject to phosphorylation in many two-component systems, decreased the ability of MviA to facilitate sigmaS turnover in vivo confirming that phosphorylation of MviA increases MviA activity.
J Mol Microbiol Biotechnol 2000 Apr
PMID:Regulation of sigma S degradation in Salmonella enterica var typhimurium: in vivo interactions between sigma S, the response regulator MviA(RssB) and ClpX. 1093 50

The Bacillus subtilis clpX and clpP genes are the sites of pleiotropic mutations that adversely affect growth on a variety of media and impair developmental processes such as sporulation and competence development. ClpX is necessary for the post-exponential induction of genes that require the sigmaH form of RNA polymerase for transcription. Both ClpX and ClpP are required for the activation of sigmaA-dependent transcription of the srf operon that encodes surfactin synthetase and the regulatory peptide ComS, required for the development of genetic competence. Transcription of srf is activated by the two-component regulatory system ComPA in response to the peptide pheromone, ComX, which mediates cell density-dependent control. A clpX mutant, although able to produce ComX, is unable to respond to the pheromone. A mutant allele of comP, encoding a product whose activity is independent of ComX, is not able to suppress clpX with respect to srf expression, suggesting that ClpXP acts at the level of ComA-dependent activation of srf transcription initiation. Suppressor mutations of clpX (cxs-1 and cxs-2) were isolated in screens for pseudorevertants exhibiting high levels of srf expression and sigmaH-dependent transcription respectively. One mutation, cxs-1, suppressed a clpP null mutation with respect to srf transcription, but did not overcome the block conferred by clpP on competence development and sporulation. Both cxs-1 and cxs-2 mutations map to the region of the rpoA gene encoding the RNA polymerase alpha C-terminal domain (alphaCTD). The reconstruction of the cxs-1 and cxs-2 alleles of rpoA confirmed that these mutations confer the suppressor phenotype. These findings provide further support for the hypothesis that ClpX and ClpP might be intimately associated with transcription initiation in B. subtilis.
Mol Microbiol 2000 Aug
PMID:Mutations conferring amino acid residue substitutions in the carboxy-terminal domain of RNA polymerase alpha can suppress clpX and clpP with respect to developmentally regulated transcription in Bacillus subtilis. 1097 8

Most bacterial proteins are stable, with half-lives considerably longer than the generation time. In Escherichia coli, the few exceptions are unstable regulatory proteins. The results presented here indicate that the first enzyme in methionine biosynthesis - homoserine trans-succinylase (HTS) - is unstable and subject to energy-dependent proteolysis. The enzyme is stable in triple mutants defective in Lon-, HslVU- and ClpP-dependent proteases. The instability of the protein is determined by the amino-terminal part of the protein, and its removal or substitution by the N-terminal part of beta-galactosidase confers stability. The effect of the amino-terminal segment is not caused by the N-end rule, as substitution of the first amino acid does not affect the stability of the protein. HTS is the first biosynthetic E. coli enzyme shown to have a short half-life and may represent a group of biosynthetic enzymes whose expression is controlled by proteolysis. Alternatively, the proteolytic processing of HTS may be unique to this enzyme and could reflect its central role in regulating bacterial growth, especially at elevated temperatures.
Mol Microbiol 2000 Sep
PMID:Control of methionine biosynthesis in Escherichia coli by proteolysis. 1099 74

CtsR (class three stress gene repressor) negatively regulates the expression of class III heat shock genes (clpP, clpE and the clpC operon) by binding to a directly repeated heptanucleotide operator sequence (A/GGTCAAA NAN A/GGTCAAA). CtsR-dependent genes are expressed at a low level at 37 degrees C and are strongly induced under heat shock conditions. We performed a structure/function analysis of the CtsR protein, which is highly conserved among low G+C Gram-positive bacteria. Random chemical mutagenesis, in vitro cross-linking, in vivo co-expression of wild-type and mutant forms of CtsR and the construction of chimeric proteins with the DNA-binding domain of the lambda CI repressor allowed us to identify three different functional domains within CtsR: a helix-turn-helix DNA-binding domain, a dimerization domain and a putative heat-sensing domain. We provide evidence suggesting that CtsR is active as a dimer. Transcriptional analysis of a clpP'-bgaB fusion and/or Western blotting experiments using antibodies directed against the CtsR protein indicate that ClpP and ClpX are involved in CtsR degradation at 37 degrees C. This in turn leads to a low steady-state level of CtsR within the cell, as CtsR negatively autoregulates its own synthesis. This is the first example of degradation of a repressor of stress response genes by the Clp ATP-dependent protease.
Mol Microbiol 2000 Oct
PMID:The CtsR regulator of stress response is active as a dimer and specifically degraded in vivo at 37 degrees C. 1106 59


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>