251
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Frees D, Savijoki K, Varmanen P, Ingmer H. Clp ATPases and ClpP proteolytic complexes regulate vital biological processes in low GC, Gram-positive bacteria. Mol Microbiol 2007; 63:1285-95. [PMID: 17302811 DOI: 10.1111/j.1365-2958.2007.05598.x] [Citation(s) in RCA: 212] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Clp proteolytic complexes consisting of a proteolytic core flanked by Clp ATPases are widely conserved in bacteria, and their biological roles have received considerable interest. In particular, mutants in the clp genes in the low-GC-content Gram-positive phyla Bacillales and Lactobacillales display a diverse range of phenotypic changes including general stress sensitivity, aberrant cell morphology, failure to initiate developmental programs, and for pathogens, severely attenuated virulence. Extensive research dedicated to unravelling the molecular mechanisms underlying these complex phenotypes has led to fascinating new insights that will be covered by this review. First, Clp ATPases and ClpP-containing proteolytic complexes play indispensable roles in cellular protein quality control systems by refolding or degrading damaged proteins in both stressed and non-stressed cells. Secondly, ClpP proteases and the chaperone activity of Clp ATPases are important for controlling stability and activity of central transcriptional regulators, thereby exerting tremendous impact on cell physiology. Targets include major stress regulators like Spx (oxidative stress), the antisigma factor RsiW (alkaline stress) and HdiR (DNA damage) in addition to regulators of developmental programs like ComK (competence development), sigmaH and Sda (sporulation). Thus, Clp proteins are central in co-ordinating developmental decisions and stress response in low GC Gram-positive bacteria.
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Affiliation(s)
- Dorte Frees
- Department of Veterinary Pathobiology, Faculty of Life Sciences, University of Copenhagen, Stigbøjlen 4, DK-1870 Frederiksberg C, Denmark
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252
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Nucleotide excision repair and homologous recombination systems commit differentially to the repair of DNA-protein crosslinks. Mol Cell 2007; 28:147-58. [PMID: 17936711 DOI: 10.1016/j.molcel.2007.07.029] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2007] [Revised: 06/30/2007] [Accepted: 07/30/2007] [Indexed: 11/21/2022]
Abstract
DNA-protein crosslinks (DPCs)-where proteins are covalently trapped on the DNA strand-block the progression of replication and transcription machineries and hence hamper the faithful transfer of genetic information. However, the repair mechanism of DPCs remains largely elusive. Here we have analyzed the roles of nucleotide excision repair (NER) and homologous recombination (HR) in the repair of DPCs both in vitro and in vivo using a bacterial system. Several lines of biochemical and genetic evidence show that both NER and HR commit to the repair or tolerance of DPCs, but differentially. NER repairs DPCs with crosslinked proteins of sizes less than 12-14 kDa, whereas oversized DPCs are processed exclusively by RecBCD-dependent HR. These results highlight how NER and HR are coordinated when cells need to deal with unusually bulky DNA lesions such as DPCs.
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253
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Luo S, McNeill M, Myers TG, Hohman RJ, Levine RL. Lon protease promotes survival of Escherichia coli during anaerobic glucose starvation. Arch Microbiol 2007; 189:181-5. [PMID: 17891379 PMCID: PMC3397802 DOI: 10.1007/s00203-007-0304-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2007] [Revised: 08/26/2007] [Accepted: 08/31/2007] [Indexed: 11/27/2022]
Abstract
In Escherichia coli, Lon is an ATP-dependent protease which degrades misfolded proteins and certain rapidly-degraded regulatory proteins. Given that oxidatively damaged proteins are generally degraded rather than repaired, we anticipated that Lon deficient cells would exhibit decreased viability during aerobic, but not anaerobic, carbon starvation. We found that the opposite actually occurs. Wild-type and Lon deficient cells survived equally well under aerobic conditions, but Lon deficient cells died more rapidly than the wild-type under anaerobiosis. Aerobic induction of the Clp family of ATP-dependent proteases could explain these results, but direct quantitation of Clp protein established that its level was not affected by Lon deficiency and overexpression of Clp did not rescue the cells under anaerobic conditions. We conclude that the Lon protease supports survival during anaerobic carbon starvation by a mechanism which does not depend on Clp.
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Affiliation(s)
| | | | - Timothy G. Myers
- Research Technologies Branch, National Institute of Allergy and Infectious Diseases, NIH, 5640 Fishers Lane, Rockville, MD 20852 USA
| | - Robert J. Hohman
- Research Technologies Branch, National Institute of Allergy and Infectious Diseases, NIH, 5640 Fishers Lane, Rockville, MD 20852 USA
| | - Rodney L. Levine
- Corresponding author: Laboratory of Biochemistry, NHLBI, Building 50, Room 2351, Bethesda, MD 20892-8012 USA. Phone +1 301 496 2310. Fax +1 301 496 0599
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254
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Wang C, Li M, Dong D, Wang J, Ren J, Otto M, Gao Q. Role of ClpP in biofilm formation and virulence of Staphylococcus epidermidis. Microbes Infect 2007; 9:1376-83. [PMID: 17890122 DOI: 10.1016/j.micinf.2007.06.012] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2007] [Revised: 05/08/2007] [Accepted: 06/26/2007] [Indexed: 10/23/2022]
Abstract
Infections caused by the leading nosocomial pathogen Staphylococcus epidermidis are characterized by biofilm formation on implanted medical devices. However, the molecular basis of biofilm formation and its regulation are not completely understood. Here, we describe an important role of the ClpP protease in biofilm development and virulence of S. epidermidis. We constructed an isogenic clpP mutant strain of a biofilm-forming clinical isolate of S. epidermidis. The mutant strain showed decreased biofilm formation in vitro and reduced virulence in a rat model of biofilm-associated infection. Biofilm forming ability of the mutant strain could be restored by expressing clpP on a plasmid, but not when a catalytically inactive allele of clpP gene was introduced. These observations indicate that the peptidase function of ClpP determines its role in biofilm formation. Experimental data in this work also suggested that clpP influenced initial attachment of bacteria on the plastic surface, the first step of biofilm formation. Furthermore, clpP was found to be regulated by the quorum-sensing agr, suggesting that part of the previously described influence of agr on the initial attachment to plastic surfaces may be mediated by clpP.
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Affiliation(s)
- Chongzhen Wang
- Key Laboratory of Medical Molecular Virology, Shanghai Medical College, Fudan University, Shanghai 200032, PR China
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255
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Führer F, Müller A, Baumann H, Langklotz S, Kutscher B, Narberhaus F. Sequence and Length Recognition of the C-terminal Turnover Element of LpxC, a Soluble Substrate of the Membrane-bound FtsH Protease. J Mol Biol 2007; 372:485-96. [PMID: 17651755 DOI: 10.1016/j.jmb.2007.06.083] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2007] [Revised: 06/06/2007] [Accepted: 06/26/2007] [Indexed: 11/17/2022]
Abstract
The membrane-anchored FtsH protease is essential in Escherichia coli as it adjusts the cellular amount of LpxC, the key enzyme in lipopolysaccharide (LPS) biosynthesis. Both accumulation and depletion of LpxC are toxic to E. coli. By continuous proteolysis of LpxC, FtsH maintains a low concentration of LpxC and, hence, the proper equilibrium between LPS and phospholipids. The C terminus of LpxC is required for turnover. By adding this tail to glutathione-S-transferase (GST) we show that it is necessary but not sufficient for FtsH-mediated degradation. A detailed mutational analysis revealed six non-polar residues in the C terminus of LpxC that are critical for degradation. Alteration of the C-terminal AVLA motif towards the SsrA-like sequence ALAA directed LpxC to other cellular proteases reinforcing the importance of the C-terminal tail for targeting to FtsH. Short C-terminal truncations stabilized LpxC. Most mutations in the C terminus of LpxC left its enzymatic activity intact as was shown by growth assays, microscopy and 2-keto-3-deoxyoctonate (KDO) determination. The critical length of the turnover element was defined by internal deletions. A C-terminal tail of about 20 amino acids length is required for proteolysis of LpxC by FtsH.
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Affiliation(s)
- Frank Führer
- Lehrstuhl für Biologie der Mikroorganismen, Ruhr-Universität Bochum, Universitätsstrasse 150, NDEF 06/783, 44780, Bochum, Germany
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256
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Prepiak P, Dubnau D. A peptide signal for adapter protein-mediated degradation by the AAA+ protease ClpCP. Mol Cell 2007; 26:639-47. [PMID: 17560370 PMCID: PMC2041856 DOI: 10.1016/j.molcel.2007.05.011] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2006] [Revised: 02/20/2007] [Accepted: 05/15/2007] [Indexed: 11/26/2022]
Abstract
ComS is an antiadaptor protein that binds to MecA, displacing the competence transcription factor ComK. This protects ComK from degradation by the ClpCP protease and turns on the switch leading to bistable gene expression. Here we identify the motifs on ComK and ComS that mediate binding to MecA, and we show that they contain similar core sequences (FMLYPK and IILYPR, respectively), located near the C and N termini of the respective proteins. A 17 residue peptide from ComK including this sequence has the same affinity for MecA as full-length ComK, and a peptide containing this sequence is sufficient to target green fluorescent protein for degradation in vivo. Crosslinking and competition experiments demonstrate that ComK- and ComS-derived peptides bind to the same region of MecA. We propose a model in which the antiadaptor protein ComS acts by direct competition to protect ComK from degradation.
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Affiliation(s)
- Peter Prepiak
- Public Health Research Institute, 225 Warren Street, Newark, NJ 07103, USA
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257
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Huesgen PF, Scholz P, Adamska I. The serine protease HhoA from Synechocystis sp. strain PCC 6803: substrate specificity and formation of a hexameric complex are regulated by the PDZ domain. J Bacteriol 2007; 189:6611-8. [PMID: 17616590 PMCID: PMC2045181 DOI: 10.1128/jb.00883-07] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Enzymes of the ATP-independent Deg serine endopeptidase family are very flexible with regard to their substrate specificity. Some family members cleave only one substrate, while others act as general proteases on unfolded substrates. The proteolytic activity of Deg proteases is regulated by PDZ protein interaction domains. Here we characterized the HhoA protease from Synechocystis sp. strain PCC 6803 in vitro using several recombinant protein constructs. The proteolytic activity of HhoA was found to increase with temperature and basic pH and was stimulated by the addition of Mg(2+) or Ca(2+). We found that the single PDZ domain of HhoA played a critical role in regulating protease activity and in the assembly of a hexameric complex. Deletion of the PDZ domain strongly reduced proteolysis of a sterically challenging resorufin-labeled casein substrate, but unlabeled beta-casein was still degraded. Reconstitution of the purified HhoA with total membrane proteins isolated from Synechocystis sp. wild-type strain PCC 6803 and a DeltahhoA mutant resulted in specific degradation of selected proteins at elevated temperatures. We concluded that a single PDZ domain of HhoA plays a critical role in defining the protease activity and oligomerization state, combining the functions that are attributed to two PDZ domains in the homologous DegP protease from Escherichia coli. Based on this first enzymatic study of a Deg protease from cyanobacteria, we propose a general role for HhoA in the quality control of extracytoplasmic proteins, including membrane proteins, in Synechocystis sp. strain PCC 6803.
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Affiliation(s)
- Pitter F Huesgen
- Department of Physiology and Plant Biochemistry, University of Konstanz, Universitätsstrasse 10, D-78457 Konstanz, Germany
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258
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Reeves A, Gerth U, Völker U, Haldenwang WG. ClpP modulates the activity of the Bacillus subtilis stress response transcription factor, sigmaB. J Bacteriol 2007; 189:6168-75. [PMID: 17586624 PMCID: PMC1951893 DOI: 10.1128/jb.00756-07] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The general stress regulon of Bacillus subtilis is controlled by the activity state of sigmaB, a transcription factor that is switched on following exposure to either physical or nutritional stress. ClpP is the proteolytic component of an ATP-dependent protease that is essential for the proper regulation of multiple adaptive responses in B. subtilis. Among the proteins whose abundance increases in ClpP- B. subtilis are several known to depend on sigmaB for their expression. In the current work we examine the relationship of ClpP to the activity of sigmaB. The data reveal that the loss of ClpP in otherwise wild-type B. subtilis results in a small increase in sigmaB activity during growth and a marked enhancement of sigmaB activity following its induction by either physical or nutritional stress. It appears to be the persistence of sigmaB's activity rather than its induction that is principally affected by the loss of ClpP. sigmaB-dependent reporter gene activity rose in parallel in ClpP+ and ClpP- B. subtilis strains but failed to display its normal transience in the ClpP- strain. The putative ClpP targets are likely to be stress generated and novel. Enhanced sigmaB activity in ClpP- B. subtilis was triggered by physical stress but not by the induced synthesis of the physical stress pathway's positive regulator (RsbT). In addition, Western blot analyses failed to detect differences in the levels of the principal known sigmaB regulators in ClpP+ and ClpP- B. subtilis strains. The data suggest a model in which ClpP facilitates the turnover of stress-generated factors, which persist in ClpP's absence to stimulate ongoing sigmaB activity.
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Affiliation(s)
- Adam Reeves
- Department of Microbiology and Immunology, MC7758, University of Texas Health Science Center, 7703 Floyd Curl Dr., San Antonio, TX 78229-3900, USA
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259
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Krishnan HB, Kim WS, Sun-Hyung J. Calcium regulates the production of nodulation outer proteins (Nops) and precludes pili formation by Sinorhizobium fredii USDA257, a soybean symbiont. FEMS Microbiol Lett 2007; 271:59-64. [PMID: 17391367 DOI: 10.1111/j.1574-6968.2007.00698.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
Sinorhizobium fredii USDA257 forms nitrogen-fixing nodules on primitive soybean cultivars such as 'Peking' but is unable to establish efficient symbiosis with North American cultivars. USDA257 when grown in presence of genistein, a potent nodD-inducing isoflavonoid, secretes at least six nodulation outer proteins (NopX, NopB, NopL, NopP, NopA and NopC) to the extracellular milieu through a type III secretion system. These proteins regulate legume nodulation in a host-specific manner. Here, it is demonstrated that calcium prevents the accumulation of NopB and NopA, and drastically reduces that of NopX and NopL. The inhibitory effect on Nops accumulation appears to be mediated specifically by calcium since other divalent cations such as Mg(2+) and Mn(2+) had no detectable effect. Calcium does not appear to interfere with the secretion of these proteins since Western blot analysis revealed that these Nops do not accumulate inside the cell. The inhibitory effect of calcium on Nops production is mediated at the posttranscriptional level. Studies by the authors indicate that the production of Nops, which function as determinants of host-range, is regulated by calcium.
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Affiliation(s)
- Hari B Krishnan
- Plant Genetics Research Unit, Agricultural Research Service, United States Department of Agriculture, University of Missouri, Columbia, MO 65211, USA.
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260
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Jain R, Chan MK. Support for a potential role of E. coli oligopeptidase A in protein degradation. Biochem Biophys Res Commun 2007; 359:486-90. [PMID: 17553460 DOI: 10.1016/j.bbrc.2007.05.142] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2007] [Accepted: 05/18/2007] [Indexed: 11/28/2022]
Abstract
Protein degradation is an essential quality control and regulatory function in organisms ranging from bacteria to eukaryotes. In bacteria, this process is initiated by ATP-dependent proteases which digest proteins to short peptides that are subsequently hydrolyzed to smaller fragments and free amino acids. While the entire genome of Escherichia coli has been sequenced, identification of endopeptidases that perform this downstream hydrolysis remains incomplete. However, in eukaryotes, thimet oligopeptidases (TOP) has been shown to hydrolyze peptides generated by the degradation of proteins by the 26S proteasome. These findings motivated us to investigate whether E. coli oligopeptidase A (OpdA), a homolog of TOP might play a similar general role in bacterial protein degradation. Herein, we provide initial support for this hypothesis by demonstrating that OpdA efficiently cleaves the peptides generated by the activity of the three primary ATP-dependent proteases from E. coli-Lon, HslUV, and ClpAP.
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Affiliation(s)
- Rinku Jain
- The Ohio State University Biophysics Program, The Ohio State University, 484 West 12th Avenue, Columbus, OH 43210, USA
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261
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Eydallin G, Viale AM, Morán-Zorzano MT, Muñoz FJ, Montero M, Baroja-Fernández E, Pozueta-Romero J. Genome-wide screening of genes affecting glycogen metabolism in Escherichia coli K-12. FEBS Lett 2007; 581:2947-53. [PMID: 17543954 DOI: 10.1016/j.febslet.2007.05.044] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2007] [Revised: 05/11/2007] [Accepted: 05/15/2007] [Indexed: 11/19/2022]
Abstract
A systematic and comprehensive gene-disrupted mutant collection of E. coli K-12 was used to identify genes whose deletions affect glycogen accumulation. Of the 3985 non-essential gene mutants of the collection, 35 displayed a glycogen-excess phenotype, whereas 30 displayed either glycogen-less or glycogen-deficient phenotypes. The genes whose deletions affect glycogen accumulation were classified into various functional categories, including energy production, envelope composition and integrity, protein translation and stability, transport of inorganic ions and nucleotides, and metabolism of carbohydrates and amino acids. The overall data indicate that glycogen metabolism is highly interconnected with a wide variety of cellular processes in E. coli.
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Affiliation(s)
- Gustavo Eydallin
- Instituto de Agrobiotecnología, Universidad Pública de Navarra, Gobierno de Navarra, Consejo Superior de Investigaciones Científicas, Mutiloako etorbidea zenbaki gabe, Mutiloabeiti, Nafarroa, Spain
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262
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Kobiler O, Rokney A, Oppenheim AB. Phage lambda CIII: a protease inhibitor regulating the lysis-lysogeny decision. PLoS One 2007; 2:e363. [PMID: 17426811 PMCID: PMC1838920 DOI: 10.1371/journal.pone.0000363] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2006] [Accepted: 03/21/2007] [Indexed: 11/18/2022] Open
Abstract
The ATP-dependent protease FtsH (HflB) complexed with HflKC participates in post-translational control of the lysis-lysogeny decision of bacteriophage lambda by rapid degradation of lambda CII. Both phage-encoded proteins, the CII transcription activator and the CIII polypeptide, are required for efficient lysogenic response. The conserved CIII is both an inhibitor and substrate of FtsH. Here we show that the protease inhibitor CIII is present as oligomeric amphipathic alpha helical structures and functions as a competitive inhibitor of FtsH by preventing binding of the CII substrate. We identified single alanine substitutions in CIII that abolish its activity. We characterize a dominant negative effect of a CIII mutant. Thus, we suggest that CIII oligomrization is required for its function. Real-time analysis of CII activity demonstrates that the effect of CIII is not seen in the absence of either FtsH or HflKC. When CIII is provided ectopically, CII activity increases linearly as a function of the multiplicity of infection, suggesting that CIII enhances CII stability and the lysogenic response. FtsH function is essential for cellular viability as it regulates the balance in the synthesis of phospholipids and lipopolysaccharides. Genetic experiments confirmed that the CIII bacteriostatic effects are due to inhibition of FtsH. Thus, the early presence of CIII following infection stimulates the lysogenic response, while its degradation at later times ensures the reactivation of FtsH allowing the growth of the established lysogenic cell.
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Affiliation(s)
- Oren Kobiler
- Department of Molecular Genetics and Biotechnology, The Hebrew University-Hadassah Medical School, Jerusalem, Israel.
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263
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Su J, Yang J, Zhao D, Kawula TH, Banas JA, Zhang JR. Genome-wide identification of Francisella tularensis virulence determinants. Infect Immun 2007; 75:3089-101. [PMID: 17420240 PMCID: PMC1932872 DOI: 10.1128/iai.01865-06] [Citation(s) in RCA: 149] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Francisella tularensis is a gram-negative pathogen that causes life-threatening infections in humans and has potential for use as a biological weapon. The genetic basis of the F. tularensis virulence is poorly understood. This study screened a total of 3,936 transposon mutants of the live vaccine strain for infection in a mouse model of respiratory tularemia by signature-tagged mutagenesis. We identified 341 mutants attenuated for infection in the lungs. The transposon disruptions were mapped to 95 different genes, virtually all of which are also present in the genomes of other F. tularensis strains, including human pathogenic F. tularensis strain Schu S4. A small subset of these attenuated mutants carried insertions in the genes encoding previously known virulence factors, but the majority of the identified genes have not been previously linked to F. tularensis virulence. Among these are genes encoding putative membrane proteins, proteins associated with stress responses, metabolic proteins, transporter proteins, and proteins with unknown functions. Several attenuated mutants contained disruptions in a putative capsule locus which partially resembles the poly-gamma-glutamate capsule biosynthesis locus of Bacillus anthracis, the anthrax agent. Deletional mutation analysis confirmed that this locus is essential for F. tularensis virulence.
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Affiliation(s)
- Jingliang Su
- Center for Immunology and Microbial Disease, Albany Medical College, 47 New Scotland Avenue, Albany, NY 12208, USA
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264
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Mizrahi I, Biran D, Gur E, Ron EZ. Tools for the study of protein quality control systems: use of truncated homoserine trans-succinylase as a model substrate for ATP-dependent proteolysis in Escherichia coli. J Microbiol Methods 2007; 70:82-5. [PMID: 17490766 DOI: 10.1016/j.mimet.2007.03.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2006] [Revised: 03/26/2007] [Accepted: 03/26/2007] [Indexed: 10/23/2022]
Abstract
Protein quality control, mediated by chaperones and ATP-dependent proteases, is essential for maintaining balanced growth and for regulating critical processes. To study these systems it is necessary to have model substrate proteins. However, most cellular proteins are stable and the few unstable proteins are usually regulatory and present in low concentrations, making them unsuitable for studies, especially in vivo. We present HTS(Delta1-6), a truncated homoserine trans-succinylase (HTS) which is unstable, can be expressed at high levels and has an enzymatic, measurable, activity. This protein can serve as a good model substrate for Escherichia coli ATP-dependent proteolysis.
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Affiliation(s)
- Itzhak Mizrahi
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Tel Aviv, 69978 Israel
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265
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Abstract
Recent genomic analyses revealed a surprisingly large number of toxin-antitoxin loci in free-living prokaryotes. The antitoxins are proteins or antisense RNAs that counteract the toxins. Two antisense RNA-regulated toxin-antitoxin gene families, hok/sok and ldr, are unrelated sequence-wise but have strikingly similar properties at the level of gene and RNA organization. Recently, two SOS-induced toxins were found to be regulated by RNA antitoxins. One such toxin, SymE, exhibits similarity with MazE antitoxin and, surprisingly, inhibits translation. Thus, it is possible that an ancestral antitoxin gene evolved into the present toxin gene (symE) whose translation is repressed by an RNA antitoxin (SymR).
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Affiliation(s)
- Kenn Gerdes
- Institute for Cell and Molecular Biosciences, Medical School, Newcastle University, Newcastle NE2 4HH, UK.
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266
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Abstract
Phagocytosis with macrophages provides a specialized mechanism for regulated ingestion and intracellular destruction of bacteria. Bacteria are first engulfed by endocytosis into a phagosome. The fusion of phagosomes and lysosomes releases toxic products that kill most bacteria and degrade them into fragments. Debris from dead bacteria is then released by exocytosis. However, some bacteria that survive within host phagocytes have evolved strategies to escape the bactericidal mechanisms associated with phagocytosis: i) antiphagocytosis (Yersinia), ii) escaping from the phagosome into cytoplasm (Listeria), and iii) remodeling their phagosome by inhibiting the maturation of phagosomes (Salmonella, Mycobacterium, Legionella). In this review, I first summarize various strategies by bacteria to avoid phagocytosis by emphasizing the steps that have been subverted by bacteria. Then, I highlight the mechanisms for surviving phagocytosis by Salmonella, with a focus on the induction of macrophage-apoptosis and modulation of membrane traffic in host cells.
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Affiliation(s)
- Tomoko Yamamoto
- Department of Microbiology and Molecular Genetics, Graduate School of Pharmaceutical Sciences, Chiba University, Japan.
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267
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Festa RA, Pearce MJ, Darwin KH. Characterization of the proteasome accessory factor (paf) operon in Mycobacterium tuberculosis. J Bacteriol 2007; 189:3044-50. [PMID: 17277063 PMCID: PMC1855869 DOI: 10.1128/jb.01597-06] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In a previous screen for Mycobacterium tuberculosis mutants that are hypersusceptible to reactive nitrogen intermediates (RNI), two genes associated with the M. tuberculosis proteasome were identified. One of these genes, pafA (proteasome accessory factor A), encodes a protein of unknown function. In this work, we determined that pafA is in an operon with two additional genes, pafB and pafC. In order to assess the contribution of these genes to RNI resistance, we isolated mutants with transposon insertions in pafB and pafC. In contrast to the pafA mutant, the pafB and pafC mutants were not severely sensitized to RNI, but pafB and pafC were nonetheless required for full RNI resistance. We also found that PafB and PafC interact with each other and that each is likely required for the stability of the other protein in M. tuberculosis. Finally, we show that the presence of PafA, but not PafB or PafC, regulates the steady-state levels of three proteasome substrates. Taken together, these data demonstrate that PafA, but not PafB or PafC, is critical for maintaining the steady-state levels of known proteasome substrates, whereas all three proteins appear to play a role in RNI resistance.
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Affiliation(s)
- Richard A Festa
- New York University School of Medicine, Department of Microbiology, 550 First Avenue, Medical Sciences Building Room 236, New York, NY 10016, USA
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268
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Graef M, Seewald G, Langer T. Substrate recognition by AAA+ ATPases: distinct substrate binding modes in ATP-dependent protease Yme1 of the mitochondrial intermembrane space. Mol Cell Biol 2007; 27:2476-85. [PMID: 17261594 PMCID: PMC1899909 DOI: 10.1128/mcb.01721-06] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The energy-dependent proteolysis of cellular proteins is mediated by conserved proteolytic AAA(+) complexes. Two such machines, the m- and i-AAA proteases, are present in the mitochondrial inner membrane. They exert chaperone-like properties and specifically degrade nonnative membrane proteins. However, molecular mechanisms of substrate engagement by AAA proteases remained elusive. Here, we define initial steps of substrate recognition and identify two distinct substrate binding sites in the i-AAA protease subunit Yme1. Misfolded polypeptides are recognized by conserved helices in proteolytic and AAA domains. Structural modeling reveals a lattice-like arrangement of these helices at the surface of hexameric AAA protease ring complexes. While helices within the AAA domain apparently play a general role for substrate binding, the requirement for binding to surface-exposed helices within the proteolytic domain is determined by the folding and membrane association of substrates. Moreover, an assembly factor of cytochrome c oxidase, Cox20, serves as a substrate-specific cofactor during proteolysis and modulates the initial interaction of nonassembled Cox2 with the protease. Our findings therefore reveal the existence of alternative substrate recognition pathways within AAA proteases and shed new light on molecular mechanisms ensuring the specificity of proteolysis by energy-dependent proteases.
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Affiliation(s)
- Martin Graef
- Institut für Genetik, Universität zu Köln, Zülpicher Strasse 47, 50674 Köln, Germany
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269
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A proteomic study of Corynebacterium glutamicum AAA+ protease FtsH. BMC Microbiol 2007; 7:6. [PMID: 17254330 PMCID: PMC1794413 DOI: 10.1186/1471-2180-7-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2006] [Accepted: 01/25/2007] [Indexed: 11/18/2022] Open
Abstract
Background The influence of the membrane-bound AAA+ protease FtsH on membrane and cytoplasmic proteins of Corynebacterium glutamicum was investigated in this study. For the analysis of the membrane fraction, anion exchange chromatography was combined with SDS-PAGE, while the cytoplasmic protein fraction was studied by conventional two-dimensional gel electrophoresis. Results In contrast to the situation in other bacteria, deletion of C. glutamicum ftsH has no significant effect on growth in standard minimal medium or response to heat or osmotic stress. On the proteome level, deletion of the ftsH gene resulted in a strong increase of ten cytoplasmic and membrane proteins, namely biotin carboxylase/biotin carboxyl carrier protein (accBC), glyceraldehyde-3-phosphate dehydrogenase (gap), homocysteine methyltransferase (metE), malate synthase (aceB), isocitrate lyase (aceA), a conserved hypothetical protein (NCgl1985), succinate dehydrogenase A (sdhA), succinate dehydrogenase B (sdhB), succinate dehydrogenase CD (sdhCD), and glutamate binding protein (gluB), while 38 cytoplasmic and membrane-associated proteins showed a decreased abundance. The decreasing amount of succinate dehydrogenase A (sdhA) in the cytoplasmic fraction of the ftsH mutant compared to the wild type and its increasing abundance in the membrane fraction indicates that FtsH might be involved in the cleavage of a membrane anchor of this membrane-associated protein and by this changes its localization. Conclusion The data obtained hint to an involvement of C. glutamicum FtsH protease mainly in regulation of energy and carbon metabolism, while the protease is not involved in stress response, as found in other bacteria.
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270
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Pruteanu M, Neher SB, Baker TA. Ligand-controlled proteolysis of the Escherichia coli transcriptional regulator ZntR. J Bacteriol 2007; 189:3017-25. [PMID: 17220226 PMCID: PMC1855835 DOI: 10.1128/jb.01531-06] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Proteases play a crucial role in remodeling the bacterial proteome in response to changes in cellular environment. Escherichia coli ZntR, a zinc-responsive transcriptional regulator, was identified by proteomic experiments as a likely ClpXP substrate, suggesting that protein turnover may play a role in regulation of zinc homeostasis. When intracellular zinc levels are high, ZntR activates expression of ZntA, an ATPase essential for zinc export. We find that ZntR is degraded in vivo in a manner dependent on both the ClpXP and Lon proteases. However, ZntR degradation decreases in the presence of high zinc concentrations, the level of ZntR rises, and transcription of the zntA exporter is increased. Mutagenesis experiments reveal that zinc binding does not appear to be solely responsible for the zinc-induced protection from proteolysis. Therefore, we tested whether DNA binding was important in the zinc-induced stabilization of ZntR by mutagenesis of the DNA binding helices. Replacement of a conserved arginine (R19A) in the DNA binding domain both enhances ZntR degradation and abolishes zinc-induced transcriptional activation of zntA. Biochemical and physical analysis of ZntR(R19A) demonstrates that it is structurally similar to, and binds zinc as well as does, the wild-type protein but is severely defective in binding DNA. Thus, we conclude that two different ligands-zinc and DNA-function together to increase ZntR stability and that ligand-controlled proteolysis of ZntR plays an important role in fine-tuning zinc homeostasis in bacteria.
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Affiliation(s)
- Mihaela Pruteanu
- Massachusetts Institute of Technology, Department of Biology, 68-523, 77 Massachusetts Ave., Cambridge, MA 02139, USA.
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271
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Abstract
Clp ATPases are protein machines involved in protein degradation and disaggregation. The common structural feature of Clp ATPases is the formation of ring-shaped oligomers. Recent work has shown that the function of all Clp ATPases is based on an energy-dependent threading of substrates through the narrow pore at the centre of the ring. This review gives an outline of known mechanistic principles of threading machines that unfold protein substrates either before their degradation (ClpA, ClpX, HslU) or during their reactivation from aggregates (ClpB). The place of Clp ATPases within a broad AAA+ superfamily of ATPases associated with various cellular activities suggests that similar mechanisms can be used by other protein machines to induce conformational rearrangements in a wide variety of substrates.
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Affiliation(s)
- Michal Zolkiewski
- Department of Biochemistry, Kansas State University, Manhattan, KS 66506, USA.
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272
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Huesgen PF, Schuhmann H, Adamska I. Photodamaged D1 protein is degraded inArabidopsismutants lacking the Deg2 protease. FEBS Lett 2006; 580:6929-32. [PMID: 17157840 DOI: 10.1016/j.febslet.2006.11.058] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2006] [Revised: 11/21/2006] [Accepted: 11/27/2006] [Indexed: 01/07/2023]
Abstract
In plants exposed to high irradiances of visible light, the D1 protein in the reaction center of photosystem II is oxidatively damaged and rapidly degraded. Earlier work in our laboratory showed that the serine protease Deg2 performs the primary cleavage of photodamaged D1 protein in vitro. Here, we demonstrate that the rate of D1 protein degradation under light stress conditions in Arabidopsis mutants lacking the Deg2 protease is similar to those in wild-type plants. Therefore, we propose that several redundant D1 protein degradation pathways might exist in vivo.
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Affiliation(s)
- Pitter F Huesgen
- Department of Biology, University of Konstanz, Universitätsstrasse 10, D-78457 Konstanz, Germany
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273
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Lessner FH, Venters BJ, Keiler KC. Proteolytic adaptor for transfer-messenger RNA-tagged proteins from alpha-proteobacteria. J Bacteriol 2006; 189:272-5. [PMID: 17085560 PMCID: PMC1797230 DOI: 10.1128/jb.01387-06] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have identified an analog of SspB, the proteolytic adaptor for transfer-messenger RNA (tmRNA)-tagged proteins, in Caulobacter crescentus. C. crescentus SspB shares limited sequence similarity with Escherichia coli SspB but binds the tmRNA tag in vitro and is required for optimal proteolysis of tagged proteins in vivo.
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Affiliation(s)
- Faith H Lessner
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, 401 Althouse Laboratory, University Park, PA 16802, USA
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274
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Pearce MJ, Arora P, Festa RA, Butler-Wu SM, Gokhale RS, Darwin KH. Identification of substrates of the Mycobacterium tuberculosis proteasome. EMBO J 2006; 25:5423-32. [PMID: 17082771 PMCID: PMC1636610 DOI: 10.1038/sj.emboj.7601405] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2006] [Accepted: 10/05/2006] [Indexed: 11/09/2022] Open
Abstract
The putative proteasome-associated proteins Mpa (Mycobaterium proteasomal ATPase) and PafA (proteasome accessory factor A) of the human pathogen Mycobacterium tuberculosis (Mtb) are essential for virulence and resistance to nitric oxide. However, a direct link between the proteasome protease and Mpa or PafA has never been demonstrated. Furthermore, protein degradation by bacterial proteasomes in vitro has not been accomplished, possibly due to the failure to find natural degradation substrates or other necessary proteasome co-factors. In this work, we identify the first bacterial proteasome substrates, malonyl Co-A acyl carrier protein transacylase and ketopantoate hydroxymethyltransferase, enzymes that are required for the biosynthesis of fatty acids and polyketides that are essential for the pathogenesis of Mtb. Maintenance of the physiological levels of these enzymes required Mpa and PafA in addition to proteasome protease activity. Mpa levels were also regulated in a proteasome-dependent manner. Finally, we found that a conserved tyrosine of Mpa was essential for function. Thus, these results suggest that Mpa, PafA, and the Mtb proteasome degrade bacterial proteins that are important for virulence in mice.
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Affiliation(s)
- Michael J Pearce
- Department of Microbiology, New York University School of Medicine, New York, NY, USA
| | - Pooja Arora
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, India
| | - Richard A Festa
- Department of Microbiology, New York University School of Medicine, New York, NY, USA
| | - Susan M Butler-Wu
- Department of Microbiology, New York University School of Medicine, New York, NY, USA
| | - Rajesh S Gokhale
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, India
| | - K Heran Darwin
- Department of Microbiology, New York University School of Medicine, New York, NY, USA
- Department of Microbiology, New York University School of Medicine, 550 First Avenue, Medical Sciences Building Room 236, New York, NY 10016, USA. Tel.: +1 212 263 2624; Fax: +1 212 263 8276; E-mail:
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275
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Goldman BS, Nierman WC, Kaiser D, Slater SC, Durkin AS, Eisen JA, Ronning CM, Barbazuk WB, Blanchard M, Field C, Halling C, Hinkle G, Iartchuk O, Kim HS, Mackenzie C, Madupu R, Miller N, Shvartsbeyn A, Sullivan SA, Vaudin M, Wiegand R, Kaplan HB. Evolution of sensory complexity recorded in a myxobacterial genome. Proc Natl Acad Sci U S A 2006; 103:15200-5. [PMID: 17015832 PMCID: PMC1622800 DOI: 10.1073/pnas.0607335103] [Citation(s) in RCA: 335] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Myxobacteria are single-celled, but social, eubacterial predators. Upon starvation they build multicellular fruiting bodies using a developmental program that progressively changes the pattern of cell movement and the repertoire of genes expressed. Development terminates with spore differentiation and is coordinated by both diffusible and cell-bound signals. The growth and development of Myxococcus xanthus is regulated by the integration of multiple signals from outside the cells with physiological signals from within. A collection of M. xanthus cells behaves, in many respects, like a multicellular organism. For these reasons M. xanthus offers unparalleled access to a regulatory network that controls development and that organizes cell movement on surfaces. The genome of M. xanthus is large (9.14 Mb), considerably larger than the other sequenced delta-proteobacteria. We suggest that gene duplication and divergence were major contributors to genomic expansion from its progenitor. More than 1,500 duplications specific to the myxobacterial lineage were identified, representing >15% of the total genes. Genes were not duplicated at random; rather, genes for cell-cell signaling, small molecule sensing, and integrative transcription control were amplified selectively. Families of genes encoding the production of secondary metabolites are overrepresented in the genome but may have been received by horizontal gene transfer and are likely to be important for predation.
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Affiliation(s)
- B. S. Goldman
- *Monsanto Company, St. Louis, MO 63167
- To whom correspondence may be addressed. E-mail:
| | - W. C. Nierman
- The Institute for Genomic Research, Rockville, MD 20850
- Department of Biochemistry and Molecular Biology, George Washington University, Washington, DC 20052
| | - D. Kaiser
- Departments of Biochemistry and Developmental Biology, Stanford University, Stanford, CA 94305
- To whom correspondence may be addressed at:
Department of Developmental Biology, B300 Beckman Center, 279 Campus Drive, Stanford, CA 94305. E-mail:
| | - S. C. Slater
- *Monsanto Company, St. Louis, MO 63167
- **Biodesign Institute, Arizona State University, Tempe, AZ 85287-5001; and
| | - A. S. Durkin
- The Institute for Genomic Research, Rockville, MD 20850
| | - J. A. Eisen
- The Institute for Genomic Research, Rockville, MD 20850
| | - C. M. Ronning
- The Institute for Genomic Research, Rockville, MD 20850
| | | | | | - C. Field
- *Monsanto Company, St. Louis, MO 63167
| | | | - G. Hinkle
- *Monsanto Company, St. Louis, MO 63167
| | | | - H. S. Kim
- The Institute for Genomic Research, Rockville, MD 20850
| | - C. Mackenzie
- Department of Microbiology and Molecular Genetics, University of Texas Medical School, Houston, TX 77030
| | - R. Madupu
- The Institute for Genomic Research, Rockville, MD 20850
| | - N. Miller
- *Monsanto Company, St. Louis, MO 63167
| | | | | | - M. Vaudin
- *Monsanto Company, St. Louis, MO 63167
| | | | - H. B. Kaplan
- Department of Microbiology and Molecular Genetics, University of Texas Medical School, Houston, TX 77030
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276
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Mizrahi I, Biran D, Ron EZ. Requirement for the acetyl phosphate pathway in Escherichia coli ATP-dependent proteolysis. Mol Microbiol 2006; 62:201-11. [PMID: 16987178 DOI: 10.1111/j.1365-2958.2006.05360.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Protein degradation is a central component of the protein quality control system. Here we show that efficient proteolysis in Escherichia coli requires the active acetyl phosphate pathway. Deletion of this pathway, leading to depletion of acetyl phosphate, results in temperature sensitivity and reduced rate of ATP-dependent proteolysis. The effect on proteolysis is general, as can be seen from the slowing down of the degradation of unstable proteins, including puromycin-derived peptides. In addition, reduced intracellular concentrations of acetyl phosphate brings about an increase in the levels of protein aggregates, which contain a wide range of proteins, as expected if a broad spectrum of substrates are involved. Additional outcomes of acetyl phosphate deficiency are elevation in the transcript levels of heat shock genes and increased thermotolerance. In E. coli the acetyl phosphate pathway is the only source of acetyl phosphate, which is a key metabolic compound involved in major cellular processes. In this communication we present evidence for the general role of the acetyl phosphate pathway in protein degradation.
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Affiliation(s)
- Itzhak Mizrahi
- Department of Molecular Microbiology and Biotechnology, The George S. Wise Faculty of Life Sciences, Tel-Aviv University, Tel-Aviv 69978, Israel
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277
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Tsilibaris V, Maenhaut-Michel G, Van Melderen L. Biological roles of the Lon ATP-dependent protease. Res Microbiol 2006; 157:701-13. [PMID: 16854568 DOI: 10.1016/j.resmic.2006.05.004] [Citation(s) in RCA: 155] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2006] [Revised: 05/22/2006] [Accepted: 05/23/2006] [Indexed: 12/24/2022]
Abstract
The Lon ATP-dependent protease plays a major role in protein quality control. An increasing number of regulatory proteins, however, are being identified as Lon substrates, thus indicating that in addition to its housekeeping function, Lon plays an important role in regulating many biological processes in bacteria. This review presents and discusses the involvement of Lon in different aspects of bacterial physiology, including cell differentiation, sporulation, pathogenicity and survival under starvation conditions.
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Affiliation(s)
- Virginie Tsilibaris
- Laboratoire de Génétique des Procaryotes, IBMM, Université Libre de Bruxelles, 12 rue des Professeurs Jeener et Brachet, 6041 Gosselies, Belgium
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278
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Rotanova TV, Botos I, Melnikov EE, Rasulova F, Gustchina A, Maurizi MR, Wlodawer A. Slicing a protease: structural features of the ATP-dependent Lon proteases gleaned from investigations of isolated domains. Protein Sci 2006; 15:1815-28. [PMID: 16877706 PMCID: PMC2242575 DOI: 10.1110/ps.052069306] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
ATP-dependent Lon proteases are multi-domain enzymes found in all living organisms. All Lon proteases contain an ATPase domain belonging to the AAA(+) superfamily of molecular machines and a proteolytic domain with a serine-lysine catalytic dyad. Lon proteases can be divided into two subfamilies, LonA and LonB, exemplified by the Escherichia coli and Archaeoglobus fulgidus paralogs, respectively. The LonA subfamily is defined by the presence of a large N-terminal domain, whereas the LonB subfamily has no such domain, but has a membrane-spanning domain that anchors the protein to the cytoplasmic side of the membrane. The two subfamilies also differ in their consensus sequences. Recent crystal structures for several individual domains and sub-fragments of Lon proteases have begun to illuminate similarities and differences in structure-function relationships between the two subfamilies. Differences in orientation of the active site residues in several isolated Lon protease domains point to possible roles for the AAA(+) domains and/or substrates in positioning the catalytic residues within the active site. Structures of the proteolytic domains have also indicated a possible hexameric arrangement of subunits in the native state of bacterial Lon proteases. The structure of a large segment of the N-terminal domain has revealed a folding motif present in other protein families of unknown function and should lead to new insights regarding ways in which Lon interacts with substrates or other cellular factors. These first glimpses of the structure of Lon are heralding an exciting new era of research on this ancient family of proteases.
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Affiliation(s)
- Tatyana V Rotanova
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow
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279
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Meyer D, Bühler B, Schmid A. Process and catalyst design objectives for specific redox biocatalysis. ADVANCES IN APPLIED MICROBIOLOGY 2006; 59:53-91. [PMID: 16829256 DOI: 10.1016/s0065-2164(06)59003-3] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Daniel Meyer
- Department of Biochemical and Chemical Engineering, University of Dortmund, Emil-Figge-Strasse 66 D-44227 Dortmund, Germany
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280
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Michel A, Agerer F, Hauck CR, Herrmann M, Ullrich J, Hacker J, Ohlsen K. Global regulatory impact of ClpP protease of Staphylococcus aureus on regulons involved in virulence, oxidative stress response, autolysis, and DNA repair. J Bacteriol 2006; 188:5783-96. [PMID: 16885446 PMCID: PMC1540084 DOI: 10.1128/jb.00074-06] [Citation(s) in RCA: 164] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Staphylococcus aureus is an important pathogen, causing a wide range of infections including sepsis, wound infections, pneumonia, and catheter-related infections. In several pathogens ClpP proteases were identified by in vivo expression technologies to be important for virulence. Clp proteolytic complexes are responsible for adaptation to multiple stresses by degrading accumulated and misfolded proteins. In this report clpP, encoding the proteolytic subunit of the ATP-dependent Clp protease, was deleted, and gene expression of DeltaclpP was determined by global transcriptional analysis using DNA-microarray technology. The transcriptional profile reveals a strong regulatory impact of ClpP on the expression of genes encoding proteins that are involved in the pathogenicity of S. aureus and adaptation of the pathogen to several stresses. Expression of the agr system and agr-dependent extracellular virulence factors was diminished. Moreover, the loss of clpP leads to a complete transcriptional derepression of genes of the CtsR- and HrcA-controlled heat shock regulon and a partial derepression of genes involved in oxidative stress response, metal homeostasis, and SOS DNA repair controlled by PerR, Fur, MntR, and LexA. The levels of transcription of genes encoding proteins involved in adaptation to anaerobic conditions potentially regulated by an Fnr-like regulator were decreased. Furthermore, the expression of genes whose products are involved in autolysis was deregulated, leading to enhanced autolysis in the mutant. Our results indicate a strong impact of ClpP proteolytic activity on virulence, stress response, and physiology in S. aureus.
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Affiliation(s)
- Antje Michel
- Institut für Molekulare Infektionsbiologie, Röntgenring 11, D-97070 Würzburg, Germany
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281
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Schoehn G, Vellieux FMD, Asunción Durá M, Receveur-Bréchot V, Fabry CMS, Ruigrok RWH, Ebel C, Roussel A, Franzetti B. An archaeal peptidase assembles into two different quaternary structures: A tetrahedron and a giant octahedron. J Biol Chem 2006; 281:36327-37. [PMID: 16973604 DOI: 10.1074/jbc.m604417200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cellular proteolysis involves large oligomeric peptidases that play key roles in the regulation of many cellular processes. The cobalt-activated peptidase TET1 from the hyperthermophilic Archaea Pyrococcus horikoshii (PhTET1) was found to assemble as a 12-subunit tetrahedron and as a 24-subunit octahedral particle. Both quaternary structures were solved by combining x-ray crystallography and cryoelectron microscopy data. The internal organization of the PhTET1 particles reveals highly self-compartmentalized systems made of networks of access channels extended by vast catalytic chambers. The two edifices display aminopeptidase activity, and their organizations indicate substrate navigation mechanisms different from those described in other large peptidase complexes. Compared with the tetrahedron, the octahedron forms a more expanded hollow structure, representing a new type of giant peptidase complex. PhTET1 assembles into two different quaternary structures because of quasi-equivalent contacts that previously have only been identified in viral capsids.
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Affiliation(s)
- Guy Schoehn
- Laboratoire de Virologie Moléculaire et Structurale c/o EMBL, FRE 2854 CNRS-UJF, 38042 Grenoble, France
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282
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Lee I, Berdis AJ, Suzuki CK. Recent developments in the mechanistic enzymology of the ATP-dependent Lon protease from Escherichia coli: highlights from kinetic studies. MOLECULAR BIOSYSTEMS 2006; 2:477-83. [PMID: 17216028 DOI: 10.1039/b609936j] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Lon protease, also known as protease La, is one of the simplest ATP-dependent proteases that plays vital roles in maintaining cellular functions by selectively eliminating misfolded, damaged and certain short-lived regulatory proteins. Although Lon is a homo-oligomer, each subunit of Lon contains both an ATPase and a protease active site. This relatively simple architecture compared to other hetero-oligomeric ATP-dependent proteases such as the proteasome makes Lon a useful paradigm for studying the mechanism of ATP-dependent proteolysis. In this article, we survey some recent developments in the mechanistic characterization of Lon with an emphasis on the utilization of pre-steady-state enzyme kinetic techniques to determine the timing of the ATPase and peptidase activities of the enzyme.
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Affiliation(s)
- Irene Lee
- Department of Chemistry, Case Western Reserve University, Cleveland, OH 44106, USA.
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283
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Ruvolo MV, Mach KE, Burkholder WF. Proteolysis of the replication checkpoint protein Sda is necessary for the efficient initiation of sporulation after transient replication stress in Bacillus subtilis. Mol Microbiol 2006; 60:1490-508. [PMID: 16796683 DOI: 10.1111/j.1365-2958.2006.05167.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Cells of Bacillus subtilis actively co-ordinate the initiation of sporulation with DNA replication and repair. Conditions that perturb replication initiation or replication elongation induce expression of a small protein, Sda, that specifically inhibits the histidine kinases required to initiate spore development. Previously, the role of Sda has been studied during chronic blocks to DNA replication. Here we show that induction of Sda is required to delay the initiation of sporulation when replication elongation is transiently blocked or after UV irradiation. During the recovery phase, cells efficiently sporulated, but this required the proteolysis of Sda. The rapid proteolysis of Sda required the ClpXP protease and the uncharged C-terminal sequence of Sda. Replacing the last two residues of Sda, both serines, with aspartic acids markedly stabilized Sda. Strains expressing sdaDD from the endogenous sda locus were unable to efficiently initiate sporulation after transient replication stress. We conclude that the Sda replication checkpoint is required to delay the initiation of sporulation when DNA replication is transiently perturbed, and that the intrinsic instability of Sda contributes to shutting off the pathway. The Sda checkpoint thus co-ordinates early events of spore development, including the polar cell division, with successful completion of chromosome replication.
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Affiliation(s)
- Michael V Ruvolo
- Department of Biological Sciences, Stanford University, 371 Serra Mall, Stanford, CA 94305-5020, USA
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284
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Koonin EV. The origin of introns and their role in eukaryogenesis: a compromise solution to the introns-early versus introns-late debate? Biol Direct 2006; 1:22. [PMID: 16907971 PMCID: PMC1570339 DOI: 10.1186/1745-6150-1-22] [Citation(s) in RCA: 187] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2006] [Accepted: 08/14/2006] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Ever since the discovery of 'genes in pieces' and mRNA splicing in eukaryotes, origin and evolution of spliceosomal introns have been considered within the conceptual framework of the 'introns early' versus 'introns late' debate. The 'introns early' hypothesis, which is closely linked to the so-called exon theory of gene evolution, posits that protein-coding genes were interrupted by numerous introns even at the earliest stages of life's evolution and that introns played a major role in the origin of proteins by facilitating recombination of sequences coding for small protein/peptide modules. Under this scenario, the absence of spliceosomal introns in prokaryotes is considered to be a result of "genome streamlining". The 'introns late' hypothesis counters that spliceosomal introns emerged only in eukaryotes, and moreover, have been inserted into protein-coding genes continuously throughout the evolution of eukaryotes. Beyond the formal dilemma, the more substantial side of this debate has to do with possible roles of introns in the evolution of eukaryotes. RESULTS I argue that several lines of evidence now suggest a coherent solution to the introns-early versus introns-late debate, and the emerging picture of intron evolution integrates aspects of both views although, formally, there seems to be no support for the original version of introns-early. Firstly, there is growing evidence that spliceosomal introns evolved from group II self-splicing introns which are present, usually, in small numbers, in many bacteria, and probably, moved into the evolving eukaryotic genome from the alpha-proteobacterial progenitor of the mitochondria. Secondly, the concept of a primordial pool of 'virus-like' genetic elements implies that self-splicing introns are among the most ancient genetic entities. Thirdly, reconstructions of the ancestral state of eukaryotic genes suggest that the last common ancestor of extant eukaryotes had an intron-rich genome. Thus, it appears that ancestors of spliceosomal introns, indeed, have existed since the earliest stages of life's evolution, in a formal agreement with the introns-early scenario. However, there is no evidence that these ancient introns ever became widespread before the emergence of eukaryotes, hence, the central tenet of introns-early, the role of introns in early evolution of proteins, has no support. However, the demonstration that numerous introns invaded eukaryotic genes at the outset of eukaryotic evolution and that subsequent intron gain has been limited in many eukaryotic lineages implicates introns as an ancestral feature of eukaryotic genomes and refutes radical versions of introns-late. Perhaps, most importantly, I argue that the intron invasion triggered other pivotal events of eukaryogenesis, including the emergence of the spliceosome, the nucleus, the linear chromosomes, the telomerase, and the ubiquitin signaling system. This concept of eukaryogenesis, in a sense, revives some tenets of the exon hypothesis, by assigning to introns crucial roles in eukaryotic evolutionary innovation. CONCLUSION The scenario of the origin and evolution of introns that is best compatible with the results of comparative genomics and theoretical considerations goes as follows: self-splicing introns since the earliest stages of life's evolution--numerous spliceosomal introns invading genes of the emerging eukaryote during eukaryogenesis--subsequent lineage-specific loss and gain of introns. The intron invasion, probably, spawned by the mitochondrial endosymbiont, might have critically contributed to the emergence of the principal features of the eukaryotic cell. This scenario combines aspects of the introns-early and introns-late views. REVIEWERS this article was reviewed by W. Ford Doolittle, James Darnell (nominated by W. Ford Doolittle), William Martin, and Anthony Poole.
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Affiliation(s)
- Eugene V Koonin
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA.
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285
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Abstract
In all organisms there is an elevated synthesis of a select family of "stress proteins" in response to a broad array of environmentally driven stress vectors including elevated or depressed temperature, changes in pH, treatment with many classes of chemicals, ischemia, desiccation, and UV irradiation. The presence of stress proteins, often termed heat shock proteins (HSPs), has been recognized for more than four decades, and there is an extensive literature that addresses the structure and properties of HSPs, their function in normal and injured cells and tissues, and the molecular mechanisms of HSP expression in response to stress. Owing to this substantial aggregate of research, there is a growing appreciation of the potential for manipulating the magnitude and timing of elevated HSP expression to achieve targeted therapeutic objectives. The successful realization of this potential requires an understanding of the kinetics of the HSP expression process in response to sublethal stress regimens along with the ability to model the governing events in the process to design practical protocols that could be applied in therapeutic settings. Significant progress has been made in recent years in defining and developing capabilities in these two areas.
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Affiliation(s)
- Kenneth R Diller
- Department of Biomedical Engineering, University of Texas at Austin, Austin, Texas 78712-1084, USA.
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286
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Iniesta AA, McGrath PT, Reisenauer A, McAdams HH, Shapiro L. A phospho-signaling pathway controls the localization and activity of a protease complex critical for bacterial cell cycle progression. Proc Natl Acad Sci U S A 2006; 103:10935-40. [PMID: 16829582 PMCID: PMC1544152 DOI: 10.1073/pnas.0604554103] [Citation(s) in RCA: 172] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Temporally and spatially controlled master regulators drive the Caulobacter cell cycle by regulating the expression of >200 genes. Rapid clearance of the master regulator, CtrA, by the ClpXP protease is a critical event that enables the initiation of chromosome replication at specific times in the cell cycle. We show here that a previously unidentified single domain-response regulator, CpdR, when in the unphosphorylated state, binds to ClpXP and, thereby, causes its localization to the cell pole. We further show that ClpXP localization is required for CtrA proteolysis. When CpdR is phosphorylated, ClpXP is delocalized, and CtrA is not degraded. Both CtrA and CpdR are phosphorylated via the same CckA histidine kinase phospho-signaling pathway, providing a reinforcing mechanism that simultaneously activates CtrA and prevents its degradation by delocalizing the CpdR/ClpXP complex. In swarmer cells, CpdR is in the phosphorylated state, thus preventing ClpXP localization and CtrA degradation. As swarmer cells differentiate into stalked cells (G1/S transition), unphosphorylated CpdR accumulates and is localized to the stalked cell pole, where it enables ClpXP localization and CtrA proteolysis, allowing the initiation of DNA replication. Dynamic protease localization mediated by a phospho-signaling pathway is a novel mechanism to integrate spatial and temporal control of bacterial cell cycle progression.
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Affiliation(s)
| | - Patrick T. McGrath
- Departments of *Developmental Biology and
- Physics, Stanford University, Stanford, CA 94305
| | | | | | - Lucy Shapiro
- Departments of *Developmental Biology and
- To whom correspondence should be addressed. E-mail:
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287
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Abstract
Protein degradation is required for homeostasis of all living organisms. Self-compartmentalized ATP-dependent proteases are required for virulence of several pathogenic bacteria. Among the proteases implicated are ClpP and Lon, as well as the more recently identified bacterial proteasome. It is generally assumed that when a pathogen invades a host, microbial proteins become irreversibly damaged and need to be degraded. However, recent data suggest that proteolysis is also essential for virulence gene regulation. In this review, we will discuss what is known about the relationship between ATP-dependent proteolysis and pathogenesis. In addition, we will propose other potential roles these chambered proteases may have in bacterial virulence. Importantly, these proteases show promise as targets for antimicrobial therapy.
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Affiliation(s)
- Susan M Butler
- Department of Microbiology, New York University School of Medicine, 550 First Avenue, New York, NY 10016, USA
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288
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Bougdour A, Wickner S, Gottesman S. Modulating RssB activity: IraP, a novel regulator of sigma(S) stability in Escherichia coli. Genes Dev 2006; 20:884-97. [PMID: 16600914 PMCID: PMC1472289 DOI: 10.1101/gad.1400306] [Citation(s) in RCA: 131] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The sigma(S) subunit of Escherichia coli RNA polymerase regulates the expression of stationary phase and stress response genes. sigma(S) is highly unstable in exponentially growing cells, whereas its stability increases dramatically upon starvation or under certain stress conditions. The degradation of sigma(S) is controlled by the phosphorylatable adaptor protein RssB and the ClpXP protease. RssB specifically directs sigma(S) to ClpXP. An unanswered question is how RssB-mediated degradation of sigma(S) is blocked by conditions such as glucose or phosphate starvation. We report here the identification and characterization of a new regulator of sigma(S) stability, IraP (inhibitor of RssB activity during phosphate starvation), that stabilizes sigma(S) both in vivo and in vitro. Deletion of iraP interferes with sigma(S) stabilization during phosphate starvation, but not during carbon starvation, and has a partial effect in stationary phase and nitrogen starvation. IraP interferes with RssB-dependent degradation of sigma(S) through a direct protein-protein interaction with RssB. A point mutant of IraP was isolated and found to be defective both for inhibition of sigma(S) degradation and interaction with RssB. Our results reveal a novel mechanism of regulation of sigma(S) stability through the regulation of RssB activity and identify IraP as a member of a new class of regulators, the anti-adaptor proteins.
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Affiliation(s)
- Alexandre Bougdour
- Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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289
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Okuno T, Yamanaka K, Ogura T. An AAA protease FtsH can initiate proteolysis from internal sites of a model substrate, apo-flavodoxin. Genes Cells 2006; 11:261-8. [PMID: 16483314 DOI: 10.1111/j.1365-2443.2006.00940.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Escherichia coli FtsH, which belongs to the AAA (ATPases associated with diverse cellular activities) family, is an ATP-dependent and membrane-bound protease. FtsH degrades misassembled membrane proteins and a subset of cytoplasmic regulatory proteins. It has been proposed that ATP-dependent proteases unfold substrate proteins and initiate a processive proteolysis from either terminus of the substrate polypeptide. We have found that FtsH degrades E. coli apo-flavodoxin (apo-Fld) but not holo-Fld containing non-covalently bound flavin mononucleotide (FMN). A mutant Fld carrying a substitution of Tyr94 to Asp (Fld(YD)) with a lower affinity for FMN was efficiently degraded by FtsH. To elucidate the directionality of Fld(YD) degradation by FtsH, we constructed several Fld(YD) fusion proteins with glutathione S-transferase (GST), green fluorescent protein (GFP), or both GST and GFP. It was found that FtsH was able to initiate degradation of the Fld(YD) moiety even when it was sandwiched by GST and GFP. Evidence indicated that FtsH can initiate proteolysis of GST-Fld(YD)-GFP from the Fld(YD) moiety by translocating an internal loop to the protease chamber in an ATP-dependent manner and that, at least, the proteolysis in the C to N direction proceeds processively.
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Affiliation(s)
- Takashi Okuno
- Division of Molecular Cell Biology, Institute of Molecular Embryology and Genetics, Kumamoto University, Kumamoto 860-0811, Japan
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290
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Jiang X, Rubio A, Chiba S, Pogliano K. Engulfment-regulated proteolysis of SpoIIQ: evidence that dual checkpoints control sigma activity. Mol Microbiol 2006; 58:102-15. [PMID: 16164552 PMCID: PMC2885156 DOI: 10.1111/j.1365-2958.2005.04811.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
During Bacillus subtilis sporulation, the engulfment checkpoint is thought to directly regulate late forespore transcription but to indirectly regulate late mother cell transcription, via the sigmaG-produced protease SpoIVB. We here demonstrate that SpoIIQ is subject to sigmaG-independent, but engulfment-dependent, proteolysis that depends on SpoIVB. Thus, SpoIVB produced before engulfment supports some SpoIVB-dependent events, suggesting that its activity or access to substrates must be regulated by engulfment. Furthermore, a mutation (bofA) that allows sigmaK to be active without sigmaG does not allow sigmaK activity in engulfment mutants, although the pro-sigmaK processing enzyme (SpoIVFB) is localized to the septum in engulfment mutants, suggesting that engulfment comprises a second checkpoint for sigmaK Finally, we find that SpoIIQ and another protein required for sigmaG activity (SpoIIIAH), which directly interact and assemble helical structures around the forespore, recruit the sigmaK-processing enzyme SpoIVFB to the forespore and these structures. We suggest that these foci serve a synapse-like role, allowing engulfment to simultaneously control both sigmaG and sigmaK, and integrating multiple checkpoints and signalling pathways.
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Affiliation(s)
| | | | | | - Kit Pogliano
- For correspondence. ; Tel. (+1) 858 822 1314; Fax (+1) 858 822 1431
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291
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McGrath PT, Iniesta AA, Ryan KR, Shapiro L, McAdams HH. A dynamically localized protease complex and a polar specificity factor control a cell cycle master regulator. Cell 2006; 124:535-47. [PMID: 16469700 DOI: 10.1016/j.cell.2005.12.033] [Citation(s) in RCA: 144] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2005] [Revised: 11/22/2005] [Accepted: 12/12/2005] [Indexed: 11/29/2022]
Abstract
Regulated proteolysis is essential for cell cycle progression in both prokaryotes and eukaryotes. We show here that the ClpXP protease, responsible for the degradation of multiple bacterial proteins, is dynamically localized to specific cellular positions in Caulobacter where it degrades colocalized proteins. The CtrA cell cycle master regulator, that must be cleared from the Caulobacter cell to allow the initiation of chromosome replication, interacts with the ClpXP protease at the cell pole where it is degraded. We have identified a novel, conserved protein, RcdA, that forms a complex with CtrA and ClpX in the cell. RcdA is required for CtrA polar localization and degradation by ClpXP. The localization pattern of RcdA is coincident with and dependent upon ClpX localization. Thus, a dynamically localized ClpXP proteolysis complex in concert with a cytoplasmic factor provides temporal and spatial specificity to protein degradation during a bacterial cell cycle.
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292
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Okuno T, Yamanaka K, Ogura T. Characterization of mutants of the Escherichia coli AAA protease, FtsH, carrying a mutation in the central pore region. J Struct Biol 2006; 156:109-14. [PMID: 16563799 DOI: 10.1016/j.jsb.2006.02.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2005] [Revised: 02/02/2006] [Accepted: 02/09/2006] [Indexed: 10/24/2022]
Abstract
Escherichia coli FtsH is an ATP-dependent and membrane-bound protease, which belongs to the ATPases associated with diverse cellular activities family. FtsH degrades a subset of cytoplasmic regulatory proteins and misassembled membrane proteins. It has been proposed that ATP-dependent proteases unfold and translocate substrate proteins into the protease chamber. Previously, we reported that Phe228 and Gly230 in the conserved motif, @XG (where @ is an aromatic residue and X is any residue), in the central pore of the FtsH ATPase ring have important roles in proteolysis and its coupling to ATP hydrolysis. In this paper, we constructed and characterized additional pore mutants. Results indicated that certain acidic residues located in the pore region are also important for the activity of FtsH. Proteolytic activities of most mutants are correlated with their ATPase activities. Evidence also indicated that Val229, the 2nd residue of the @XG motif, may have a substrate-specific role.
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Affiliation(s)
- Takashi Okuno
- Division of Molecular Cell Biology, Institute of Molecular Embryology and Genetics, Kumamoto University, Kumamoto 860-0811, Japan
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293
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Graciet E, Hu RG, Piatkov K, Rhee JH, Schwarz EM, Varshavsky A. Aminoacyl-transferases and the N-end rule pathway of prokaryotic/eukaryotic specificity in a human pathogen. Proc Natl Acad Sci U S A 2006; 103:3078-83. [PMID: 16492767 PMCID: PMC1413915 DOI: 10.1073/pnas.0511224103] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The N-end rule relates the in vivo half-life of a protein to the identity of its N-terminal residue. Primary destabilizing N-terminal residues (Nd(p)) are recognized directly by the targeting machinery. The recognition of secondary destabilizing N-terminal residues (Nd(s)) is preceded by conjugation of an Nd(p) residue to Nd(s) of a polypeptide substrate. In eukaryotes, ATE1-encoded arginyl-transferases (R(D,E,C*)-transferases) conjugate Arg (R), an Nd(p) residue, to Nd(s) residues Asp (D), Glu (E), or oxidized Cys residue (C*). Ubiquitin ligases recognize the N-terminal Arg of a substrate and target the (ubiquitylated) substrate to the proteasome. In prokaryotes such as Escherichia coli, Nd(p) residues Leu (L) or Phe (F) are conjugated, by the aat-encoded Leu/Phe-transferase (L/F(K,R)-transferase), to N-terminal Arg or Lys, which are Nd(s) in prokaryotes but Nd(p) in eukaryotes. In prokaryotes, substrates bearing the Nd(p) residues Leu, Phe, Trp, or Tyr are degraded by the proteasome-like ClpAP protease. Despite enzymological similarities between eukaryotic R(D,E,C*)-transferases and prokaryotic L/F(K,R)-transferases, there is no significant sequelogy (sequence similarity) between them. We identified an aminoacyl-transferase, termed Bpt, in the human pathogen Vibrio vulnificus. Although it is a sequelog of eukaryotic R(D,E,C*)-transferases, this prokaryotic transferase exhibits a "hybrid" specificity, conjugating Nd(p) Leu to Nd(s) Asp or Glu. Another aminoacyl-transferase, termed ATEL1, of the eukaryotic pathogen Plasmodium falciparum, is a sequelog of prokaryotic L/F(K,R)-transferases (Aat), but has the specificity of eukaryotic R(D,E,C*)-transferases (ATE1). Phylogenetic analysis suggests that the substrate specificity of R-transferases arose by two distinct routes during the evolution of eukaryotes.
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Affiliation(s)
- Emmanuelle Graciet
- Division of Biology, California Institute of Technology, Pasadena, CA 91125; and
| | - Rong-Gui Hu
- Division of Biology, California Institute of Technology, Pasadena, CA 91125; and
| | - Konstantin Piatkov
- Division of Biology, California Institute of Technology, Pasadena, CA 91125; and
| | - Joon Haeng Rhee
- National Research Laboratory of Molecular Microbial Pathogenesis and Genome Research Center for Enteropathogenic Bacteria, Chonnam National University Medical School, Gwangju 501-746, Korea
| | - Erich M. Schwarz
- Division of Biology, California Institute of Technology, Pasadena, CA 91125; and
| | - Alexander Varshavsky
- Division of Biology, California Institute of Technology, Pasadena, CA 91125; and
- To whom correspondence should be addressed. E-mail:
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294
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Abstract
RcsC, RcsB, and RcsA were first identified as a sensor kinase, a response regulator, and an auxiliary regulatory protein, respectively, regulating the genes of capsular polysaccharide synthesis. Recent advances have demonstrated that these proteins are part of a complex phosphorelay, in which phosphate travels from the histidine kinase domain in RcsC to a response regulator domain in the same protein; from there to a phosphotransfer protein, RcsD; and from there to RcsB. In addition to capsule synthesis, which requires the unstable regulatory protein RcsA, RcsB also stimulates transcription of a small RNA, RprA; the cell division gene ftsZ; and genes encoding membrane and periplasmic proteins, including the osmotically inducible genes osmB and osmC. The Rcs system appears to play an important role in the later stages of biofilm development; induction of Rcs signaling by surfaces is consistent with this role.
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Affiliation(s)
- Nadim Majdalani
- Laboratory of Molecular Biology, National Cancer Institute, Bethesda, Maryland 20892, USA
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295
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Chen JC, Hottes AK, McAdams HH, McGrath PT, Viollier PH, Shapiro L. Cytokinesis signals truncation of the PodJ polarity factor by a cell cycle-regulated protease. EMBO J 2006; 25:377-86. [PMID: 16395329 PMCID: PMC1383518 DOI: 10.1038/sj.emboj.7600935] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2005] [Accepted: 12/02/2005] [Indexed: 11/08/2022] Open
Abstract
We demonstrate that successive cleavage events involving regulated intramembrane proteolysis (Rip) occur as a function of time during the Caulobacter cell cycle. The proteolytic substrate PodJ(L) is a polar factor that recruits proteins required for polar organelle biogenesis to the correct cell pole at a defined time in the cell cycle. We have identified a periplasmic protease (PerP) that initiates the proteolytic sequence by truncating PodJ(L) to a form with altered activity (PodJ(S)). Expression of perP is regulated by a signal transduction system that activates cell type-specific transcription programs and conversion of PodJ(L) to PodJ(S) in response to the completion of cytokinesis. PodJ(S), sequestered to the progeny swarmer cell, is subsequently released from the polar membrane by the membrane metalloprotease MmpA for degradation during the swarmer-to-stalked cell transition. This sequence of proteolytic events contributes to the asymmetric localization of PodJ isoforms to the appropriate cell pole. Thus, temporal activation of the PerP protease and spatial restriction of the polar PodJ(L) substrate cooperatively control the cell cycle-dependent onset of Rip.
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Affiliation(s)
- Joseph C Chen
- Department of Developmental Biology, Stanford University, Stanford, CA, USA
| | - Alison K Hottes
- Department of Developmental Biology, Stanford University, Stanford, CA, USA
- Department of Electrical Engineering, Stanford University, Stanford, CA, USA
| | - Harley H McAdams
- Department of Developmental Biology, Stanford University, Stanford, CA, USA
| | - Patrick T McGrath
- Department of Developmental Biology, Stanford University, Stanford, CA, USA
- Department of Physics, Stanford University, Stanford, CA, USA
| | - Patrick H Viollier
- Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, OH, USA
| | - Lucy Shapiro
- Department of Developmental Biology, Stanford University, Stanford, CA, USA
- Department of Developmental Biology, Stanford University, Beckman Center B300, Stanford, CA 94305, USA. Tel.: +1 650 725 7678; Fax: +1 650 725 7739; E-mail:
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296
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De Castro RE, Maupin-Furlow JA, Giménez MI, Herrera Seitz MK, Sánchez JJ. Haloarchaeal proteases and proteolytic systems. FEMS Microbiol Rev 2006; 30:17-35. [PMID: 16438678 DOI: 10.1111/j.1574-6976.2005.00003.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Proteases play key roles in many biological processes and have numerous applications in biotechnology and industry. Recent advances in the genetics, genomics and biochemistry of the halophilic Archaea provide a tremendous opportunity for understanding proteases and their function in the context of an archaeal cell. This review summarizes our current knowledge of haloarchaeal proteases and provides a reference for future research.
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Affiliation(s)
- Rosana E De Castro
- Instituto de Investigaciones Biológicas, Facultad de Ciencias Exactas y Naturales Universidad Nacional de Mar del Plata, Mar del Plata, Argentina.
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297
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Isaac DD, Pinkner JS, Hultgren SJ, Silhavy TJ. The extracytoplasmic adaptor protein CpxP is degraded with substrate by DegP. Proc Natl Acad Sci U S A 2005; 102:17775-9. [PMID: 16303867 PMCID: PMC1308919 DOI: 10.1073/pnas.0508936102] [Citation(s) in RCA: 122] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In Escherichia coli, the CpxR/A 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, stress-combative 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.
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Affiliation(s)
- Daniel D Isaac
- Department of Molecular Biology, Lewis Thomas Laboratory, Princeton University, Washington Road, Princeton, NJ 08544, USA
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298
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Sarma AD, Emerich DW. Global protein expression pattern of Bradyrhizobium japonicum bacteroids: a prelude to functional proteomics. Proteomics 2005; 5:4170-84. [PMID: 16254929 DOI: 10.1002/pmic.200401296] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
As a prelude to using functional proteomics towards understanding the process of symbiotic nitrogen fixation between the legume soybean and the soil bacteria Bradyrhizobium japonicum, we examined the total protein expression pattern of the nodule bacteria, often referred to as bacteroids. A partial proteome map was constructed by separating the total bacteroid proteins using high-resolution 2-DE. Of the several hundred protein spots analyzed using PMF, 180 spots were tentatively identified by searching the available database for B. japonicum, (http://www.kazusa.or.jp/index.html). The data showed that the bacteroid expressed a dominant and elaborate protein network for nitrogen and carbon metabolism, which is closely dependent on the plant supplied metabolites, and seems aptly supported by a selective group of bacteroid transporter proteins. However, they seem to lack a defined fatty acid and nucleic acid metabolism. Interestingly, the proteins related to protein synthesis, scaffolding and degradation were among the most predominant spots of the bacteroid proteome. In addition, several proteins, which showed fairly good expression, were identified to be involved with cellular detoxification, stress regulation and signaling communication components. This preliminary proteomic data matches very well with several biochemical and genetic reports, and clearly shows the inter-connection between several metabolic pathways that meet the needs of the bacteroid. It is expected that in the future this will allow us to develop testable hypotheses about the roles of several of these proteins in context to the metabolic pathway connections and metabolite fluxes.
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Affiliation(s)
- Annamraju D Sarma
- Department of Biochemistry, University of Missouri, Columbia, MO 65211, USA
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299
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Martin A, Baker TA, Sauer RT. Rebuilt AAA + motors reveal operating principles for ATP-fuelled machines. Nature 2005; 437:1115-20. [PMID: 16237435 DOI: 10.1038/nature04031] [Citation(s) in RCA: 292] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2005] [Accepted: 07/14/2005] [Indexed: 11/09/2022]
Abstract
Hexameric ring-shaped ATPases of the AAA + (for ATPases associated with various cellular activities) superfamily power cellular processes in which macromolecular structures and complexes are dismantled or denatured, but the mechanisms used by these machine-like enzymes are poorly understood. By covalently linking active and inactive subunits of the ATPase ClpX to form hexamers, here we show that diverse geometric arrangements can support the enzymatic unfolding of protein substrates and translocation of the denatured polypeptide into the ClpP peptidase for degradation. These studies indicate that the ClpX power stroke is generated by ATP hydrolysis in a single subunit, rule out concerted and strict sequential ATP hydrolysis models, and provide evidence for a probabilistic sequence of nucleotide hydrolysis. This mechanism would allow any ClpX subunit in contact with a translocating polypeptide to hydrolyse ATP to drive substrate spooling into ClpP, and would prevent stalling if one subunit failed to bind or hydrolyse ATP. Energy-dependent machines with highly diverse quaternary architectures and molecular functions could operate by similar asymmetric mechanisms.
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Affiliation(s)
- Andreas Martin
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Bernes S, Siman-Tov R, Ankri S. Epigenetic and classical activation of Entamoeba histolytica heat shock protein 100 (EHsp100) expression. FEBS Lett 2005; 579:6395-402. [PMID: 16263115 DOI: 10.1016/j.febslet.2005.09.101] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2005] [Accepted: 09/28/2005] [Indexed: 11/17/2022]
Abstract
The protozoan parasite Entamoeba histolytica expresses a cytosine-5 DNA methyltransferase (Ehmeth) that belongs to the DNMT2 protein family. The biological function of members of this DNMT2 family is unknown. In the present study, the 5' region of E. histolytica heat shock protein 100 (5'EHsp100) was isolated by affinity chromatography with 5-methylcytosine antibodies as ligand. The methylation status of 5'EHsp100 was confirmed by sodium bisulfite sequencing. We showed that the expression of EHsp100 was induced by heat shock, 5-azacytidine (5-AzaC), an inhibitor of DNA methyltransferase and Trichostatin A (TSA), an inhibitor of histone deacetylase. The effect of TSA on EHsp100 expression was rapidly reversed by removing the drug from the culture. In contrast, EHsp100 expression was still detectable one month after removing 5-AzaC from the media. Whereas 5-AzaC and TSA caused demethylation in the promoter region of EHsp100, no demethylation was observed following heat shock. Remarkably, DNA that includes three putative heat shock elements identified in the promoter region of EHsp100 bound to a protein of 37kDa present in the nuclear fraction of heat-shocked trophozoites but absent in the nuclear fraction of 5-AzaC and TSA treated trophozoites. Our data suggest that EHsp100 expression can be regulated by both a classical and an epigenetic mechanism.
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Affiliation(s)
- Sabina Bernes
- Department of Molecular Microbiology, The Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, 31096 Haifa, Israel
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