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Nemati G, Romanó A, Wahl F, Berger T, Rojo LV, Graber HU. Bovine Staphylococcus aureus: a European study of contagiousness and antimicrobial resistance. Front Vet Sci 2023; 10:1154550. [PMID: 37206433 PMCID: PMC10188956 DOI: 10.3389/fvets.2023.1154550] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Accepted: 04/04/2023] [Indexed: 05/21/2023] Open
Abstract
In dairy herds managements, mastitis is the leading cause of economic losses. One of the most important pathogens responsible for intra-mammary infections is Staphylococcus aureus. The genetic properties of S. aureus have a strong influence on its pathogenicity and contagiousness. In this study, we aimed to obtain a comprehensive overview of the key bovine S. aureus clinical properties, such as contagiousness and antimicrobial resistance, present in European strains. For this, 211 bovine S. aureus strains from ten European countries that were used in a previous study were used in this study. Contagiousness was assessed using qPCR for the detection of the marker gene adlb. Antimicrobial resistance was evaluated using a broth microdilution assay and mPCR for the detection of genes involved in penicillin resistance (blaI, blaR1, and blaZ). It was found that adlb was present in CC8/CLB strains; however, in Germany, it was found in CC97/CLI and in an unknown CC/CLR strains. CC705/CLC strains from all countries were found to be susceptible to all tested antibiotics. Major resistance to penicillin/ampicillin, chloramphenicol, clindamycin and tetracycline was detected. Resistance to oxacillin, trimethoprim/sulfamethoxazole and cephalosporins was rarely observed. In addition, contagiousness and antibiotic resistance seem to correlate with different CCs and genotypic clusters. Hence, it is recommended that multilocus sequence typing or genotyping be utilized as a clinical instrument to identify the most appropriate antibiotic to use in mastitis treatment. Actualization of the breakpoints of veterinary strains is necessary to address the existing antibiotic resistance of the bacteria involved in veterinary mastitis.
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Affiliation(s)
- Ghazal Nemati
- Food Microbial Systems, Risk Assessment and Mitigation Group, Agroscope, Bern, Switzerland
- Food Microbial Systems, Microbiological Safety of Foods of Animal Origin Group, Agroscope, Bern, Switzerland
- *Correspondence: Ghazal Nemati
| | - Alicia Romanó
- Food Microbial Systems, Microbiological Safety of Foods of Animal Origin Group, Agroscope, Bern, Switzerland
| | - Fabian Wahl
- Food Microbial Systems, Agroscope, Bern, Switzerland
| | - Thomas Berger
- Food Microbial Systems, Risk Assessment and Mitigation Group, Agroscope, Bern, Switzerland
| | - Laura Vazquez Rojo
- Food Microbial Systems, Microbiological Safety of Foods of Animal Origin Group, Agroscope, Bern, Switzerland
| | - Hans Ulrich Graber
- Food Microbial Systems, Microbiological Safety of Foods of Animal Origin Group, Agroscope, Bern, Switzerland
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Mama OM, Aspiroz C, Lozano C, Ruiz-Ripa L, Azcona JM, Seral C, Cercenado E, López-Cerero L, Palacian P, Belles-Belles A, Berdonces P, Siller M, Aguirre-Quiñonero A, Zarazaga M, Torres C. Penicillin susceptibility among invasive MSSA infections: a multicentre study in 16 Spanish hospitals. J Antimicrob Chemother 2021; 76:2519-2527. [PMID: 34245259 DOI: 10.1093/jac/dkab208] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Accepted: 05/25/2021] [Indexed: 01/04/2023] Open
Abstract
OBJECTIVES To determine the prevalence of penicillin susceptibility among MSSA causing bloodstream infections (BSIs) in 16 Spanish hospitals and to characterize the penicillin-susceptible MSSA (MSSA-PENS) isolates. METHODS A total of 1011 Staphylococcus aureus isolates were collected from blood cultures in 16 Spanish hospitals during 2018-19 (6-12 months) and their susceptibility to 18 antimicrobials was determined. The MSSA-PENS isolates were selected and examined by PCR to determine the presence of the blaZ gene, other resistance genes and the genes lukF/lukS-PV, eta, etb and tst. The immune evasion cluster (IEC) type was also analysed. All the MSSA-PENS isolates were submitted to S. aureus protein A (spa) typing and the clonal complexes (CCs) were assigned according to their spa type. RESULTS The prevalence of MSSA was 74.6% (754/1011) and 14.9% (151/1011) were MSSA-PENS-blaZnegative. MSSA-PENS-blaZnegative isolates (n = 151) were ascribed to 88 spa types and 11 CCs. The most frequent CCs were CC5 (35/151) and CC398 (25/151), with t002-CC5 and t571-CC398 being the most common lineages. Pan-susceptibility was identified in 117 of the 151 MSSA-PENS-blaZnegative isolates (77.5%). In the remaining isolates, erythromycin and clindamycin resistance was the most frequent resistance found, although tobramycin, ciprofloxacin, fusidic acid, mupirocin and/or tetracycline resistance was also detected. Thirty-eight MSSA-PENS-blaZnegative isolates were IEC negative and four isolates were Panton-Valentine leucocidin ('PVL') positive. CONCLUSIONS A high penicillin susceptibility rate was detected among MSSA, opening therapeutic opportunities for BSIs. The emergence of new successful MSSA-PENS clones could be responsible for these data. The detection among MSSA-PENS-blaZnegative isolates of the clonal lineage CC398 or the absence of an IEC raises questions about their possible animal origin, requiring further analysis.
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Affiliation(s)
| | - Carmen Aspiroz
- Servicio Microbiología, Hospital Royo Villanova, Zaragoza, Spain
| | - Carmen Lozano
- Área Bioquímica y Biología Molecular, Universidad de La Rioja, Madre de Dios 53, 26006, Logroño, Spain
| | - Laura Ruiz-Ripa
- Área Bioquímica y Biología Molecular, Universidad de La Rioja, Madre de Dios 53, 26006, Logroño, Spain
| | | | - Cristina Seral
- Servicio Microbiología, Hospital Clínico Universitario Lozano Blesa, Zaragoza, Spain
| | - Emilia Cercenado
- Servicio Microbiología, Hospital General Universitario Gregorio Marañón, CIBERES, Centro de Investigación Biomédica en Red de Enfermedades Respiratorias, Madrid, Spain
| | - Lorena López-Cerero
- Unidad de Enfermedades Infecciosas y Microbiología, Hospital Universitario Virgen Macarena, Departamento de Microbiología, Universidad de Sevilla, Instituto de Biomedicina de Sevilla, Sevilla, Spain
| | - Pilar Palacian
- Servicio Microbiología, Hospital Universitario Miguel Servet/IIS Aragón, Zaragoza, Spain
| | - Alba Belles-Belles
- Servicio Microbiología, Hospital Universitario Arnau de Vilanova, Lérida, Spain
| | | | - María Siller
- Servicio Microbiología, Hospital Universitario Marqués de Valdecilla, Santander, Spain
| | | | - Myriam Zarazaga
- Área Bioquímica y Biología Molecular, Universidad de La Rioja, Madre de Dios 53, 26006, Logroño, Spain
| | - Carmen Torres
- Área Bioquímica y Biología Molecular, Universidad de La Rioja, Madre de Dios 53, 26006, Logroño, Spain
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Belluzo BS, Abriata LA, Giannini E, Mihovilcevic D, Dal Peraro M, Llarrull LI. An experiment-informed signal transduction model for the role of the Staphylococcus aureus MecR1 protein in β-lactam resistance. Sci Rep 2019; 9:19558. [PMID: 31862951 PMCID: PMC6925264 DOI: 10.1038/s41598-019-55923-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Accepted: 12/04/2019] [Indexed: 11/13/2022] Open
Abstract
The treatment of hospital- and community-associated infections by methicillin-resistant Staphylococcus aureus (MRSA) is a perpetual challenge. This Gram-positive bacterium is resistant specifically to β-lactam antibiotics, and generally to many other antibacterial agents. Its resistance mechanisms to β-lactam antibiotics are activated only when the bacterium encounters a β-lactam. This activation is regulated by the transmembrane sensor/signal transducer proteins BlaR1 and MecR1. Neither the transmembrane/metalloprotease domain, nor the complete MecR1 and BlaR1 proteins, are isolatable for mechanistic study. Here we propose a model for full-length MecR1 based on homology modeling, residue coevolution data, a new extensive experimental mapping of transmembrane topology, partial structures, molecular simulations, and available NMR data. Our model defines the metalloprotease domain as a hydrophilic transmembrane chamber effectively sealed by the apo-sensor domain. It proposes that the amphipathic helices inserted into the gluzincin domain constitute the route for transmission of the β-lactam-binding event in the extracellular sensor domain, to the intracellular and membrane-embedded zinc-containing active site. From here, we discuss possible routes for subsequent activation of proteolytic action. This study provides the first coherent model of the structure of MecR1, opening routes for future functional investigations on how β-lactam binding culminates in the proteolytic degradation of MecI.
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Affiliation(s)
- Bruno S Belluzo
- Instituto de Biología Molecular y Celular de Rosario (IBR, CONICET-UNR), Predio CONICET Rosario, 27 de Febrero 210 bis, 2000, Rosario, Argentina
| | - Luciano A Abriata
- Laboratory for Biomolecular Modeling - École Polytechnique Fédérale de Lausanne and Swiss Institute of Bioinformatics, CH-1015, Lausanne, Switzerland
| | - Estefanía Giannini
- Instituto de Biología Molecular y Celular de Rosario (IBR, CONICET-UNR), Predio CONICET Rosario, 27 de Febrero 210 bis, 2000, Rosario, Argentina
| | - Damila Mihovilcevic
- Instituto de Biología Molecular y Celular de Rosario (IBR, CONICET-UNR), Predio CONICET Rosario, 27 de Febrero 210 bis, 2000, Rosario, Argentina
| | - Matteo Dal Peraro
- Laboratory for Biomolecular Modeling - École Polytechnique Fédérale de Lausanne and Swiss Institute of Bioinformatics, CH-1015, Lausanne, Switzerland
| | - Leticia I Llarrull
- Instituto de Biología Molecular y Celular de Rosario (IBR, CONICET-UNR), Predio CONICET Rosario, 27 de Febrero 210 bis, 2000, Rosario, Argentina. .,Área Biofísica, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 570, 2000, Rosario, Argentina.
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Srivastava SK, King KS, AbuSara NF, Malayny CJ, Piercey BM, Wilson JA, Tahlan K. In vivo functional analysis of a class A β-lactamase-related protein essential for clavulanic acid biosynthesis in Streptomyces clavuligerus. PLoS One 2019; 14:e0215960. [PMID: 31013337 PMCID: PMC6478378 DOI: 10.1371/journal.pone.0215960] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Accepted: 04/12/2019] [Indexed: 11/23/2022] Open
Abstract
In Streptomyces clavuligerus, the gene cluster involved in the biosynthesis of the clinically used β-lactamase inhibitor clavulanic acid contains a gene (orf12 or cpe) encoding a protein with a C-terminal class A β-lactamase-like domain. The cpe gene is essential for clavulanic acid production, and the recent crystal structure of its product (Cpe) was shown to also contain an N-terminal isomerase/cyclase-like domain, but the function of the protein remains unknown. In the current study, we show that Cpe is a cytoplasmic protein and that both its N- and C-terminal domains are required for in vivo clavulanic acid production in S. clavuligerus. Our results along with those from previous studies allude towards a biosynthetic role for Cpe during the later stages of clavulanic acid production in S. clavuligerus. Amino acids from Cpe essential for biosynthesis were also identified, including one (Lys89) from the recently described N-terminal isomerase-like domain of unknown function. Homologues of Cpe from other clavulanic acid-producing Streptomyces spp. were shown to be functionally equivalent to the S. clavuligerus protein, whereas those from non-producers containing clavulanic acid-like gene clusters were not. The suggested in vivo involvement of an isomerase-like domain recruited by an ancestral β-lactamase related protein, supports a previous hypothesis that Cpe could be involved in a step requiring the opening and modification of the clavulanic acid core during its biosynthesis from 5S precursors.
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Affiliation(s)
| | - Kelcey S. King
- Department of Biology, Memorial University of Newfoundland, St. John’s, NL, Canada
| | - Nader F. AbuSara
- Department of Biology, Memorial University of Newfoundland, St. John’s, NL, Canada
| | - Chelsea J. Malayny
- Department of Biology, Memorial University of Newfoundland, St. John’s, NL, Canada
| | - Brandon M. Piercey
- Department of Biology, Memorial University of Newfoundland, St. John’s, NL, Canada
| | - Jaime A. Wilson
- Department of Biology, Memorial University of Newfoundland, St. John’s, NL, Canada
| | - Kapil Tahlan
- Department of Biology, Memorial University of Newfoundland, St. John’s, NL, Canada
- * E-mail:
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5
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Hombach M, Weissert C, Senn MM, Zbinden R. Comparison of phenotypic methods for the detection of penicillinase in Staphylococcus aureus and proposal of a practical diagnostic approach. J Antimicrob Chemother 2017; 72:1089-1093. [PMID: 28069883 DOI: 10.1093/jac/dkw521] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2016] [Accepted: 11/04/2016] [Indexed: 11/14/2022] Open
Abstract
Objectives Disc diffusion is a cost-efficient, low-complexity, reliable method for detection of blaZ -mediated benzylpenicillin resistance in Staphylococcus aureus if the zone edge is inspected. EUCAST breakpoints cannot fully separate β-lactamase-positive from β-lactamase-negative strains, and EUCAST recommends the zone edge test. Literature on nitrocefin-based testing and the zone edge test is scarce with wide variations in reported assay performance. Methods This study compared two different nitrocefin-based commercial and in-house tests and the EUCAST-based zone edge test for penicillinase detection in S. aureus applying a PCR-based gold standard. Results In total, 215 non-duplicate clinical S. aureus isolates were included in the study, of which 127 (59.1%) did not harbour a blaZ gene, whereas 88 (40.9%) were blaZ positive. This study showed that for blaZ detection the zone edge test is more sensitive (96.6%) than nitrocefin tests independent of using nitrocefin discs (87.5% sensitivity) or solution (89.8% sensitivity), and that the significant inter-person variations of the zone edge test are probably related to the training level of the individual investigators (individual sensitivity ranging from 68.2% to 96.6%, specificity ranging from 89.8% to 100%). Conclusions In addition to continued and strict training of investigators, we propose mandatory checking of benzylpenicillin zone edges, particularly in an investigation zone from 26 to 30 mm, which can result in improved specificity/positive predictive value of the zone edge test (from 98.4% to 100%) but retains the high sensitivity/negative predictive value of the method.
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Affiliation(s)
- Michael Hombach
- Institut für Medizinische Mikrobiologie, Universität Zürich, Zürich 8006, Schweiz
| | | | - Maria Magdalena Senn
- Institut für Medizinische Mikrobiologie, Universität Zürich, Zürich 8006, Schweiz
| | - Reinhard Zbinden
- Institut für Medizinische Mikrobiologie, Universität Zürich, Zürich 8006, Schweiz
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6
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Li L, Wang Q, Zhang H, Yang M, Khan MI, Zhou X. Sensor histidine kinase is a β-lactam receptor and induces resistance to β-lactam antibiotics. Proc Natl Acad Sci U S A 2016; 113:1648-53. [PMID: 26831117 PMCID: PMC4760793 DOI: 10.1073/pnas.1520300113] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
β-Lactams disrupt bacterial cell wall synthesis, and these agents are the most widely used antibiotics. One of the principle mechanisms by which bacteria resist the action of β-lactams is by producing β-lactamases, enzymes that degrade β-lactams. In Gram-negative bacteria, production of β-lactamases is often induced in response to the antibiotic-associated damage to the cell wall. Here, we have identified a previously unidentified mechanism that governs β-lactamase production. In the Gram-negative enteric pathogen Vibrio parahaemolyticus, we found a histidine kinase/response regulator pair (VbrK/VbrR) that controls expression of a β-lactamase. Mutants lacking either VbrK or VbrR do not produce the β-lactamase and are no longer resistant to β-lactam antibiotics. Notably, VbrK autophosphorylation is activated by β-lactam antibiotics, but not by other lactams. However, single amino acid substitutions in the putative periplasmic binding pocket of VbrK leads its phosphorylation in response to both β-lactam and other lactams, suggesting that this kinase is a β-lactam receptor that can directly detect β-lactam antibiotics instead of detecting the damage to cell wall resulting from β-lactams. In strong support of this idea, we found that purified periplasmic sensor domain of VbrK binds penicillin, and that such binding is critical for VbrK autophosphorylation and β-lactamase production. Direct recognition of β-lactam antibiotics by a histidine kinase receptor may represent an evolutionarily favorable mechanism to defend against β-lactam antibiotics.
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Affiliation(s)
- Lu Li
- Department of Pathobiology and Veterinary Science, University of Connecticut, Storrs, CT 06269-3089
| | - Qiyao Wang
- State Key Laboratory of Bioreactor Engineering, School of Biotechnology, East China University of Science and Technology, Shanghai 200237, China
| | - Hui Zhang
- Department of Pathobiology and Veterinary Science, University of Connecticut, Storrs, CT 06269-3089; Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China
| | - Minjun Yang
- Shanghai-Ministry of Science and Technology (MOST) Key Laboratory of Health and Disease Genomics, Chinese National Human Genome Center at Shanghai, Shanghai 201203, China
| | - Mazhar I Khan
- Department of Pathobiology and Veterinary Science, University of Connecticut, Storrs, CT 06269-3089
| | - Xiaohui Zhou
- Department of Pathobiology and Veterinary Science, University of Connecticut, Storrs, CT 06269-3089;
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Gene network analysis reveals the association of important functional partners involved in antibiotic resistance: A report on an important pathogenic bacterium Staphylococcus aureus. Gene 2015; 575:253-63. [PMID: 26342962 DOI: 10.1016/j.gene.2015.08.068] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Revised: 07/30/2015] [Accepted: 08/31/2015] [Indexed: 12/27/2022]
Abstract
Staphylococcus aureus (S. aureus) is an emerging concern in hospital settings as it causes serious human infections. The multidrug resistance (MDR) in S. aureus is a complicated problem that is difficult to overcome due to the presence of numerous antibiotic resistance genes and it exhibit resistance to most of the currently available antibiotics. Presently, the resistance mechanisms of these genes/proteins are not completely understood. Therefore, identifying and understanding the functional relationship between the antibiotic resistant genes and their associated proteins might provide necessary information on resistance mechanisms and thereby help in designing successful drugs to combat the antibiotic resistance. In this study, we propose a model based on protein/gene network to identify genes/proteins associated with drug resistance in S. aureus. We filtered 50 functional partners in NorA, aacA-aphD (aac6ie), aad9ib (ant), aadd (knt), baca (uppP), bl2a_pc (blaZ), ble, ermA, SAV0052 (ermb), ermc, fosB, mecA (mecI), mecR (mecr1), mepA, msrA1, qacA, vraR (str), tet38 and tetM while 40 functional partners are identified in tet and aphA-3 (aph3iiia). The average shortest path length and betweenness centrality of functional partners in the clusters are calculated and they are functionally enriched with the Gene Ontology (GO) terms with a p-value cut-off ≤0.05. Interestingly, the constructed network reveals many associated antibiotic resistant genes and proteins and their role in resistance mechanisms. Thus, our results might provide a better understanding of the molecular mechanisms of action and their mode of drug resistance that will be useful for researchers exploring in the field of antibiotic resistance mechanisms.
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Role of the mecA gene in oxacillin resistance in a Staphylococcus aureus clinical strain with a pvl-positive ST59 genetic background. Antimicrob Agents Chemother 2013; 58:1047-54. [PMID: 24277044 DOI: 10.1128/aac.02045-13] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The most prevalent community-associated methicillin-resistant Staphylococcus aureus (C-MRSA) strains in Taiwan, sequence type 59 (ST59) clones, carry staphylococcal cassette chromosome mec (SCCmec) type V and, to a lesser extent, type IV. These strains show wide variation in sensitivity to oxacillin, but the reasons for this variation are unknown. Here we compared the sequences of the mecA genes from clinical strains of different SCCmec types and found that they contain different mecA promoter mutations. Analysis of mecA promoter activity by reporter gene fusions showed that single base substitutions in the promoter have a strong influence on mecA transcription. The different mecA variants, including promoter sequences, were expressed in the methicillin-sensitive Staphylococcus aureus (MSSA) strain C195 (ST59 background). PBP 2a production among the parental strains and strains with promoter mutant mecA genes showed a close correlation with mecA transcription levels. Furthermore, the quantity of PBP 2a also closely correlated with the level of oxacillin resistance in the C195 background. Our data suggest that mecA promoter mutations play an important role in determining the level of oxacillin resistance. The mecA promoter mutation G-25A (25 bases upstream of the mecA translation start site) was found to be associated with a high oxacillin MIC (256 μg/ml), G-7T conferred a moderate oxacillin MIC (32 to 64 μg/ml), strains with C-33T showed a low oxacillin MIC (4 to 8 μg/ml), and A-38G reversed the effect of the C-33T mutation, restoring the oxacillin resistance level in the A-38G C-33T double mutant. These observations may explain why C-MRSA strains in Taiwan carrying SCCmec type IV or V have such enormous variations in oxacillin MICs.
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Arêde P, Milheiriço C, de Lencastre H, Oliveira DC. The anti-repressor MecR2 promotes the proteolysis of the mecA repressor and enables optimal expression of β-lactam resistance in MRSA. PLoS Pathog 2012; 8:e1002816. [PMID: 22911052 PMCID: PMC3406092 DOI: 10.1371/journal.ppat.1002816] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2012] [Accepted: 06/09/2012] [Indexed: 01/20/2023] Open
Abstract
Methicillin-resistant Staphylococcus aureus (MRSA) is an important human pathogen, which is cross-resistant to virtually all β-lactam antibiotics. MRSA strains are defined by the presence of mecA gene. The transcription of mecA can be regulated by a sensor-inducer (MecR1) and a repressor (MecI), involving a unique series of proteolytic steps. The induction of mecA by MecR1 has been described as very inefficient and, as such, it is believed that optimal expression of β-lactam resistance by MRSA requires a non-functional MecR1-MecI system. However, in a recent study, no correlation was found between the presence of functional MecR1-MecI and the level of β-lactam resistance in a representative collection of epidemic MRSA strains. Here, we demonstrate that the mecA regulatory locus consists, in fact, of an unusual three-component arrangement containing, in addition to mecR1-mecI, the up to now unrecognized mecR2 gene coding for an anti-repressor. The MecR2 function is essential for the full induction of mecA expression, compensating for the inefficient induction of mecA by MecR1 and enabling optimal expression of β-lactam resistance in MRSA strains with functional mecR1-mecI regulatory genes. Our data shows that MecR2 interacts directly with MecI, destabilizing its binding to the mecA promoter, which results in the repressor inactivation by proteolytic cleavage, presumably mediated by native cytoplasmatic proteases. These observations point to a revision of the current model for the transcriptional control of mecA and open new avenues for the design of alternative therapeutic strategies for the treatment of MRSA infections. Moreover, these findings also provide important insights into the complex evolutionary pathways of antibiotic resistance and molecular mechanisms of transcriptional regulation in bacteria. Methicillin-resistance Staphylococcus aureus (MRSA) is an important human pathogen, causing a wide range of infections. MRSA strains are resistant to virtually all β-lactam antibiotics and often are also resistant to many other classes of antibiotics, leaving physicians with few therapeutic options. MRSA is defined by the presence of the mecA gene. The induction of mecA transcription in response to β-lactams involves a unique series of proteolytic steps and some critical details of this signal transduction mechanism are still illusive. For instance, it is not fully explained why the induction of mecA by its cognate regulatory genes mecR1-mecI appears to be very inefficient and it is not clear if the observed MecI repressor proteolysis is mediated directly by the activated MecR1 sensor-inducer. In this study, we demonstrate that the mecA regulatory locus is not a two-component system but instead it is a three-component system containing the previously unrecognized anti-repressor mecR2 gene. MecR2 disturbs the binding of the repressor MecI to the mecA promoter, which leads to its proteolytic inactivation independently from MecR1. Moreover, our data shows that in the presence of functional mecR1-mecI genes, mecR2 is essential for a robust induction of mecA transcription and, as consequence, for the optimal expression of β-lactam resistance.
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Affiliation(s)
- Pedro Arêde
- CREM, Department of Life Sciences, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Caparica, Portugal
| | - Catarina Milheiriço
- Laboratory of Molecular Genetics, Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Hermínia de Lencastre
- Laboratory of Molecular Genetics, Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
- Laboratory of Microbiology and Infectious Diseases, The Rockefeller University, New York, New York, United States of America
| | - Duarte C. Oliveira
- CREM, Department of Life Sciences, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Caparica, Portugal
- * E-mail:
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Llarrull LI, Mobashery S. Dissection of events in the resistance to β-lactam antibiotics mediated by the protein BlaR1 from Staphylococcus aureus. Biochemistry 2012; 51:4642-9. [PMID: 22616850 DOI: 10.1021/bi300429p] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A heterologous expression system was used to evaluate activation of BlaR1, a sensor/signal transducer protein of Staphylococcus aureus with a central role in resistance to β-lactam antibiotics. In the absence of other S. aureus proteins that might respond to antibiotics and participate in signal transduction events, we documented that BlaR1 fragmentation is autolytic, that it occurs in the absence of antibiotics, and that BlaR1 directly degrades BlaI, the gene repressor of the system. Furthermore, we disclosed that this proteolytic activity is metal ion-dependent and that it is not modulated directly by acylation of the sensor domain by β-lactam antibiotics.
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Affiliation(s)
- Leticia I Llarrull
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA
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11
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Berzigotti S, Benlafya K, Sépulchre J, Amoroso A, Joris B. Bacillus licheniformis BlaR1 L3 loop is a zinc metalloprotease activated by self-proteolysis. PLoS One 2012; 7:e36400. [PMID: 22623956 PMCID: PMC3356374 DOI: 10.1371/journal.pone.0036400] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2011] [Accepted: 04/04/2012] [Indexed: 11/26/2022] Open
Abstract
In Bacillus licheniformis 749/I, BlaP β-lactamase is induced by the presence of a β-lactam antibiotic outside the cell. The first step in the induction mechanism is the detection of the antibiotic by the membrane-bound penicillin receptor BlaR1 that is composed of two functional domains: a carboxy-terminal domain exposed outside the cell, which acts as a penicillin sensor, and an amino-terminal domain anchored to the cytoplasmic membrane, which works as a transducer-transmitter. The acylation of BlaR1 sensor domain by the antibiotic generates an intramolecular signal that leads to the activation of the L3 cytoplasmic loop of the transmitter by a single-point cleavage. The exact mechanism of L3 activation and the nature of the secondary cytoplasmic signal launched by the activated transmitter remain unknown. However, these two events seem to be linked to the presence of a HEXXH zinc binding motif of neutral zinc metallopeptidases. By different experimental approaches, we demonstrated that the L3 loop binds zinc ion, belongs to Gluzincin metallopeptidase superfamily and is activated by self-proteolysis.
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Affiliation(s)
- Stéphanie Berzigotti
- Centre for Protein Engineering, Department of Life Sciences, University of Liège, Liège, Belgium
| | - Kamal Benlafya
- Centre for Protein Engineering, Department of Life Sciences, University of Liège, Liège, Belgium
| | - Jérémy Sépulchre
- Centre for Protein Engineering, Department of Life Sciences, University of Liège, Liège, Belgium
| | - Ana Amoroso
- Centre for Protein Engineering, Department of Life Sciences, University of Liège, Liège, Belgium
| | - Bernard Joris
- Centre for Protein Engineering, Department of Life Sciences, University of Liège, Liège, Belgium
- * E-mail:
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12
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Llarrull LI, Prorok M, Mobashery S. Binding of the gene repressor BlaI to the bla operon in methicillin-resistant Staphylococcus aureus. Biochemistry 2010; 49:7975-7. [PMID: 20722402 DOI: 10.1021/bi101177a] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The expression of the gene products in many methicillin-resistant Staphylococcus aureus (MRSA) strains is regulated by the gene repressor BlaI. Here we show that BlaI is a mixture of monomer and dimer at in vivo concentrations, binds to the operator regions preferentially as a monomeric protein, and the measured dissociation constants and in vivo concentrations account for the basal level transcription of the resistance genes. These observations for the first time provide a quantitative picture of the processes that take place in the cytoplasm that lead to the induction of antibiotic resistance factors to counter the challenge by β-lactams.
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Affiliation(s)
- Leticia I Llarrull
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, USA
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13
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Boudet J, Duval V, Van Melckebeke H, Blackledge M, Amoroso A, Joris B, Simorre JP. Conformational and thermodynamic changes of the repressor/DNA operator complex upon monomerization shed new light on regulation mechanisms of bacterial resistance against beta-lactam antibiotics. Nucleic Acids Res 2007; 35:4384-95. [PMID: 17576674 PMCID: PMC1935004 DOI: 10.1093/nar/gkm448] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
In absence of β-lactam antibiotics, BlaI and MecI homodimeric repressors negatively control the expression of genes involved in β-lactam resistance in Bacillus licheniformis and in Staphylococcus aureus. Subsequently to β-lactam presence, BlaI/MecI is inactivated by a single-point proteolysis that separates its N-terminal DNA-binding domain to its C-terminal domain responsible for its dimerization. Concomitantly to this proteolysis, the truncated repressor acquires a low affinity for its DNA target that explains the expression of the structural gene for resistance. To understand the loss of the high DNA affinity of the truncated repressor, we have determined the different dissociation constants of the system and solved the solution structure of the B. licheniformis monomeric repressor complexed to the semi-operating sequence OP1 of blaP (1/2OP1blaP) by using a de novo docking approach based on inter-molecular nuclear Overhauser effects and chemical-shift differences measured on each macromolecular partner. Although the N-terminal domain of the repressor is not subject to internal structural rearrangements upon DNA binding, the molecules adopt a tertiary conformation different from the crystallographic operator–repressor dimer complex, leading to a 30° rotation of the monomer with respect to a central axis extended across the DNA. These results open new insights for the repression and induction mechanisms of bacterial resistance to β-lactams.
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Affiliation(s)
- Julien Boudet
- Institut de Biologie Structurale Jean-Pierre Ebel CEA-CNRS-UJF, 41 Avenue Jules Horowitz, 38027 Grenoble Cedex 1, France, Centre d’Ingénierie des Protéines, Institut de Chimie B6A, Université de Liège Sart-Tilman B4000, Belgium and Cátedra de Microbiología, Facultad de Farmacia y Bioquímica Universidad de Buenos Aires, Junín 954 (1113), Buenos Aires, Argentina
| | - Valérie Duval
- Institut de Biologie Structurale Jean-Pierre Ebel CEA-CNRS-UJF, 41 Avenue Jules Horowitz, 38027 Grenoble Cedex 1, France, Centre d’Ingénierie des Protéines, Institut de Chimie B6A, Université de Liège Sart-Tilman B4000, Belgium and Cátedra de Microbiología, Facultad de Farmacia y Bioquímica Universidad de Buenos Aires, Junín 954 (1113), Buenos Aires, Argentina
| | - Hélène Van Melckebeke
- Institut de Biologie Structurale Jean-Pierre Ebel CEA-CNRS-UJF, 41 Avenue Jules Horowitz, 38027 Grenoble Cedex 1, France, Centre d’Ingénierie des Protéines, Institut de Chimie B6A, Université de Liège Sart-Tilman B4000, Belgium and Cátedra de Microbiología, Facultad de Farmacia y Bioquímica Universidad de Buenos Aires, Junín 954 (1113), Buenos Aires, Argentina
| | - Martin Blackledge
- Institut de Biologie Structurale Jean-Pierre Ebel CEA-CNRS-UJF, 41 Avenue Jules Horowitz, 38027 Grenoble Cedex 1, France, Centre d’Ingénierie des Protéines, Institut de Chimie B6A, Université de Liège Sart-Tilman B4000, Belgium and Cátedra de Microbiología, Facultad de Farmacia y Bioquímica Universidad de Buenos Aires, Junín 954 (1113), Buenos Aires, Argentina
| | - Ana Amoroso
- Institut de Biologie Structurale Jean-Pierre Ebel CEA-CNRS-UJF, 41 Avenue Jules Horowitz, 38027 Grenoble Cedex 1, France, Centre d’Ingénierie des Protéines, Institut de Chimie B6A, Université de Liège Sart-Tilman B4000, Belgium and Cátedra de Microbiología, Facultad de Farmacia y Bioquímica Universidad de Buenos Aires, Junín 954 (1113), Buenos Aires, Argentina
| | - Bernard Joris
- Institut de Biologie Structurale Jean-Pierre Ebel CEA-CNRS-UJF, 41 Avenue Jules Horowitz, 38027 Grenoble Cedex 1, France, Centre d’Ingénierie des Protéines, Institut de Chimie B6A, Université de Liège Sart-Tilman B4000, Belgium and Cátedra de Microbiología, Facultad de Farmacia y Bioquímica Universidad de Buenos Aires, Junín 954 (1113), Buenos Aires, Argentina
| | - Jean-Pierre Simorre
- Institut de Biologie Structurale Jean-Pierre Ebel CEA-CNRS-UJF, 41 Avenue Jules Horowitz, 38027 Grenoble Cedex 1, France, Centre d’Ingénierie des Protéines, Institut de Chimie B6A, Université de Liège Sart-Tilman B4000, Belgium and Cátedra de Microbiología, Facultad de Farmacia y Bioquímica Universidad de Buenos Aires, Junín 954 (1113), Buenos Aires, Argentina
- *To whom correspondence should be addressed. +33-4-38785799+33-4-38785494
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Hososaka Y, Hanaki H, Endo H, Suzuki Y, Nagasawa Z, Otsuka Y, Nakae T, Sunakawa K. Characterization of oxacillin-susceptible mecA-positive Staphylococcus aureus: a new type of MRSA. J Infect Chemother 2007; 13:79-86. [PMID: 17458674 DOI: 10.1007/s10156-006-0502-7] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2006] [Accepted: 12/22/2006] [Indexed: 10/23/2022]
Abstract
Methicillin-resistant Staphylococcus aureus (MRSA) has been defined as S. aureus having the mecA gene or showing a minimum inhibitory concentration (MIC) of oxacillin higher than 4 mg/l. However, some clinical isolates are mecA-positive and oxacillin-susceptible. Therefore, we surveyed the occurrence of S. aureus having the mecA gene and an MIC of oxacillin of less than 2 mg/l (oxacillin-susceptible MRSA; OS-MRSA) in a total of 480 strains of S. aureus collected from 11 hospitals in different location in Japan isolated from 2003 through 2005. We found 6 strains matching the criteria for OS-MRSA. All 6 strains were staphylococcal cassette chromosome (SCC) mec-positive, without exception, and 4 strains showed the SCCmec type III-variant, which is unique in Japan. These OS-MRSAs were least resistant to oxacillin among the MRSAs tested and they were within the susceptible range to seven other beta-lactam antibiotics tested. Thus, OS-MRSA may become a high-resistant MRSA upon the treatment of patients with beta-lactam antibiotics. To characterize whether these OS-MRSAs were hospital-acquired or community-acquired MRSAs, we tested for the presence of the genes encoding toxins. Genes encoding hemolysin, exfoliative toxin, enterotoxin, toxic shock syndrome toxin-1, and Panton-Valentine leukocidin were found in 6, 4, 0, 0, and 0 strains, respectively. These results revealed that OS-MRSAs could be classified as a new type of MRSA that exhibits properties distinguishable from either hospital- or community-acquired MRSA. Coagulase typing of the OS-MRSAs supported the above conclusion. In this study, the occurrence of OS-MRSA at a certain frequency was noted; precautions are called for in the classification of oxacillin-resistant S. aureus and in the treatment of OS-MRSA infection.
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Affiliation(s)
- Yasuko Hososaka
- Kitasato Research Center for Anti-infection Drugs, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8642, Japan.
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15
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Fisher JF, Meroueh SO, Mobashery S. Bacterial resistance to beta-lactam antibiotics: compelling opportunism, compelling opportunity. Chem Rev 2005; 105:395-424. [PMID: 15700950 DOI: 10.1021/cr030102i] [Citation(s) in RCA: 684] [Impact Index Per Article: 36.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- Jed F Fisher
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, USA
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16
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Safo MK, Zhao Q, Ko TP, Musayev FN, Robinson H, Scarsdale N, Wang AHJ, Archer GL. Crystal structures of the BlaI repressor from Staphylococcus aureus and its complex with DNA: insights into transcriptional regulation of the bla and mec operons. J Bacteriol 2005; 187:1833-44. [PMID: 15716455 PMCID: PMC1064009 DOI: 10.1128/jb.187.5.1833-1844.2005] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The 14-kDa BlaI protein represses the transcription of blaZ, the gene encoding beta-lactamase. It is homologous to MecI, which regulates the expression of mecA, the gene encoding the penicillin binding protein PBP2a. These genes mediate resistance to beta-lactam antibiotics in staphylococci. Both repressors can bind either bla or mec DNA promoter-operator sequences. Regulated resistance genes are activated via receptor-mediated cleavage of the repressors. Cleavage is induced when beta-lactam antibiotics bind the extramembrane sensor of the sensor-transducer signaling molecules, BlaR1 or MecR1. The crystal structures of BlaI from Staphylococcus aureus, both in free form and in complex with 32 bp of DNA of the mec operator, have been determined to 2.0- and 2.7-A resolutions, respectively. The structure of MecI, also in free form and in complex with the bla operator, has been previously reported. Both repressors form homodimers, with each monomer composed of an N-terminal DNA binding domain of winged helix-turn-helix topology and a C-terminal dimerization domain. The structure of BlaI in complex with the mec operator shows a protein-DNA interface that is conserved between both mec and bla targets. The recognition helix alpha3 interacts specifically with the conserved TACA/TGTA DNA binding motif. BlaI and, probably, MecI dimers bind to opposite faces of the mec DNA double helix in an up-and-down arrangement, whereas MecI and, probably, BlaI dimers bind to the same DNA face of bla promoter-operator DNA. This is due to the different spacing of mec and bla DNA binding sites. Furthermore, the flexibility of the dimeric proteins may make the C-terminal proteolytic cleavage site more accessible when the repressors are bound to DNA than when they are in solution, suggesting that the induction cascade involves bound rather than free repressor.
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Affiliation(s)
- Martin K Safo
- Department of Medicinal Chemistry, School of Pharmacy and Institute for Structural Biology and Drug Discovery, Virginia Commonwealth University, Richmond, Virginia 23298-0049, USA
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17
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MallorquÃ-Fernández G, Marrero A, GarcÃa-Piquè S, GarcÃa-Castellanos R, Gomis-Rüth F. Staphylococcal methicillin resistance: fine focus on folds and functions. FEMS Microbiol Lett 2004. [DOI: 10.1111/j.1574-6968.2004.tb09560.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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18
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García-Castellanos R, Mallorquí-Fernández G, Marrero A, Potempa J, Coll M, Gomis-Rüth FX. On the Transcriptional Regulation of Methicillin Resistance. J Biol Chem 2004; 279:17888-96. [PMID: 14960592 DOI: 10.1074/jbc.m313123200] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Bacterial resistance to antibiotics poses a serious worldwide public health problem due to the high morbidity and mortality caused by infectious diseases. Most hospital-onset infections are associated with methicillin-resistant Staphylococcus aureus (MRSA) strains that have acquired multiple drug resistance to beta-lactam antibiotics. In a response to antimicrobial stress, nearly all clinical MRSA isolates produce beta-lactamase (BlaZ) and a penicillin-binding protein with low affinity for beta-lactam antibiotics (PBP2a, also known as PBP2' or MecA). Both effectors are regulated by homologous signal transduction systems consisting of a sensor/transducer and a transcriptional repressor. MecI (methicillin repressor) blocks mecA but also blaZ transcription and that of itself and the co-transcribed sensor/transducer. The structure of MecI in complex with a cognate operator double-stranded DNA reveals a homodimeric arrangement with a novel C-terminal spiral staircase dimerization domain responsible for dimer integrity. Each protomer interacts with the DNA major groove through a winged helix DNA-binding domain and specifically recognizes the nucleotide sequence 5'-Gua-Thy-Ade-X-Thy-3'. This results in an unusual convex bending of the DNA helix. The structure of this first molecular determinant of methicillin resistance in complex with its target DNA provides insights into its regulatory mechanism and paves the way for new antimicrobial strategies against MRSA.
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19
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Hanique S, Colombo ML, Goormaghtigh E, Soumillion P, Frère JM, Joris B. Evidence of an Intramolecular Interaction between the Two Domains of the BlaR1 Penicillin Receptor during the Signal Transduction. J Biol Chem 2004; 279:14264-72. [PMID: 14736870 DOI: 10.1074/jbc.m313488200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The BlaR1 protein is a penicillin-sensory transducer involved in the induction of the Bacillus licheniformis beta-lactamase. The amino-terminal domain of the protein exhibits four transmembrane segments (TM1-TM4) that form a four-alpha-helix bundle embedded in the plasma bilayer. The carboxyl-terminal domain of 250 amino acids (BlaR-CTD) fused at the carboxyl end of TM4 possesses the amino acid sequence signature of penicillin-binding proteins. This membrane topology suggests that BlaR-CTD and the BlaR-amino-terminal domain are responsible for signal reception and signal transduction, respectively. With the use of phage display experiments, we highlight herein an interaction between BlaR-CTD and the extracellular, 63-amino acid L2 loop connecting TM2 and TM3. This interaction does not occur in the presence of penicillin. This result suggests that binding of the antibiotic to BlaR1 might entail the release of the interaction between L2 and BlaR-CTD, causing a motion of the alpha-helix bundle and transfer of the information to the cytoplasm of the cell. In addition, fluorescence spectroscopy, CD, and Fourier transform IR spectroscopy experiments indicate that in contrast to the behavior of the corresponding Staphylococcus aureus protein, the beta-lactam antibiotic does not induce a drastic conformational change in B. licheniformis BlaR-CTD.
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Affiliation(s)
- Sophie Hanique
- Centre d'Ingénierie des Protéines, Institut de Chimie, Université de Liège, B-4000 Sart-Tilman, Belgium
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20
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García-Castellanos R, Marrero A, Mallorquí-Fernández G, Potempa J, Coll M, Gomis-Ruth FX. Three-dimensional structure of MecI. Molecular basis for transcriptional regulation of staphylococcal methicillin resistance. J Biol Chem 2003; 278:39897-905. [PMID: 12881514 DOI: 10.1074/jbc.m307199200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Methicillin-resistant Staphylococcus aureus is the main cause of nosocomial and community-onset infections that affect millions of people worldwide. Some methicillin-resistant Staphylococcus aureus infections have become essentially untreatable by beta-lactams because of acquired molecular machineries enabling antibiotic resistance. Evasion from methicillin challenge is mainly achieved by the synthesis of a penicillin-binding protein of low affinity for antibiotics, MecA, that replaces regular penicillin-binding proteins in cell wall turnover when these have been inactivated by antibiotics. MecA synthesis is regulated by a signal transduction system consisting of the sensor/transducer MecR1 and the 14-kDa transcriptional repressor MecI (also known as methicillin repressor) that constitutively blocks mecA transcription. The three-dimensional structure of MecI reveals a dimer of two independent winged helix domains, each of which binds a palindromic DNA-operator half site, and two intimately intertwining dimerization domains of novel spiral staircase architecture, held together by a hydrophobic core. Limited proteolytic cleavage by cognate MecR1 within the dimerization domains results in loss of dimer interaction surface, dissociation, and repressor release, which triggers MecA synthesis. Structural information on components of the MecA regulatory pathway, in particular on methicillin repressor, the ultimate transcriptional trigger of mecA-encoded methicillin resistance, is expected to lead to the development of new antimicrobial drugs.
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Affiliation(s)
- Raquel García-Castellanos
- Institut de Biologia Molecular de Barcelona, Centre d'Investigació i Desenvolupament/Consell Superior d'Investigacions Científiques C/Jordi Girona, 18-26, 08034 Barcelona, Spain
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21
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Filée P, Vreuls C, Herman R, Thamm I, Aerts T, De Deyn PP, Frère JM, Joris B. Dimerization and DNA binding properties of the Bacillus licheniformis 749/I BlaI repressor. J Biol Chem 2003; 278:16482-7. [PMID: 12615920 DOI: 10.1074/jbc.m210887200] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
In the absence of penicillin, the beta-lactamase encoding gene blaP of Bacillus licheniformis 749/I is negatively regulated by the transcriptional repressor BlaI. Three palindromic operator regions are recognized by BlaI: two in the blaP promoter (OP1 and OP2) and one (OP3) in the promoter of the blaI-blaR1 operon. In this study, the dissociation constant of the purified BlaI dimer was estimated at 25 microm by equilibrium ultracentrifugation. Quantitative Western blot analysis indicates that the intracellular concentrations of BlaI in B. licheniformis 749/I and Bacillus subtilis transformed by a multicopy plasmid harboring the beta-lactamase locus (blaP-blaI-blaR1) were lower than (1.9 microm) or in the same range as (75 microm) the dissociation constant, respectively. This suggests that BlaI is partially dimeric in the cytoplasm of these strains and interacts in vivo with its operators as a preformed dimer. This hypothesis is supported by band shift assays on an operator containing a randomized half-operator sequence. The global dissociation constants of the operator-BlaI dimer complexes were measured by band shift assays and estimated as K(d)(OP1) = 1.7 +/- 0.5 10(-15) m(2), K(d)(OP2) = 3.3 +/- 0.9 10(-15) m(2), and K(d)(OP3) = 10.5 +/- 2.5 10(-15) m(2). The role of the DNA binding properties of BlaI on the beta-lactamase regulation is discussed.
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Affiliation(s)
- Patrice Filée
- Centre d'ingénierie des Protéines, Institut de Chimie B6a, Université de Liège, Sart-Tilman, B4000 Liège, Belgium
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22
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Filée P, Benlafya K, Delmarcelle M, Moutzourelis G, Frère JM, Brans A, Joris B. The fate of the BlaI repressor during the induction of the Bacillus licheniformis BlaP beta-lactamase. Mol Microbiol 2002; 44:685-94. [PMID: 12022149 DOI: 10.1046/j.1365-2958.2002.02888.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The induction of the Staphylococcus aureus BlaZ and Bacillus licheniformis 749/I BlaP beta-lactamases by beta-lactam antibiotics occurs according to similar processes. In both bacteria, the products of the blaI and blaRl genes share a high degree of sequence homology and act as repressors and penicillin-sensory transducers respectively. It has been shown in S. aureus that the BlaI repressor, which controls the expression of BlaZ negatively, is degraded after the addition of the inducer. In the present study,we followed the fate of BlaI during beta-lactamase induction in B. licheniformis 749/I and in a recombinant Bacillus subtilis 168 strain harbouring the pDML995 plasmid, which carries the B. licheniformis blaP, blaI and blaRl genes. In contrast to the situation in B. licheniformis 749/I, beta-lactamase induction in B.subtilis 168/pDML995 was not correlated with the proteolysis of BlaI. To exclude molecular variations undetectable by SDS-PAGE, two-dimensional gel electrophoresis was performed with cellular extracts from uninduced or induced B. subtilis 168/pDML995cells. No variation in the Blal isoelectric point was observed in induced cells, whereas the DNA-binding property was lost. Cross-linking experiments with dithiobis(succimidylpropionate) confirmed that, in uninduced recombinant B. subtilis cells, BlaI was present as a homodimer and that this situation was not altered in induced conditions. This latter result is incompatible with a mechanism of inactivation of BlaI by proteolysis and suggests that the inactivation of BlaI results from a non-covalent modification by a co-activator and that the subsequent proteolysis of BlaI might be a secondary phenomenon. In addition to the presence of this co-activator, our results show that the presence of penicillin stress is also required for full induction of beta-lactamase biosynthesis.
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Affiliation(s)
- Patrice Filée
- Centre d'Ingénierie des Protéines, Institut de Chimie B6a, Université de Liège, Sart-Tilman, B4000, Belgium
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