1
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Deforet F, Carrière R, Dufour PL'A, Prat R, Desbiolles C, Cottin N, Reuzeau A, Dauwalder O, Dupieux-Chabert C, Tristan A, Cecchini T, Lemoine J, Vandenesch F. Proteomic assay for rapid characterisation of Staphylococcus aureus antimicrobial resistance mechanisms directly from blood cultures. Eur J Clin Microbiol Infect Dis 2024; 43:1329-1342. [PMID: 38750334 DOI: 10.1007/s10096-024-04811-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2024] [Accepted: 03/11/2024] [Indexed: 07/20/2024]
Abstract
PURPOSE Staphylococcus aureus is one of the most common pathogens causing bloodstream infection. A rapid characterisation of resistance to methicillin and, occasionally, to aminoglycosides for particular indications, is therefore crucial to quickly adapt the treatment and improve the clinical outcomes of septic patients. Among analytical technologies, targeted liquid chromatography-tandem mass spectrometry (LC-MS/MS) has emerged as a promising tool to detect resistance mechanisms in clinical samples. METHODS A rapid proteomic method was developed to detect and quantify the most clinically relevant antimicrobial resistance effectors in S. aureus in the context of sepsis: PBP2a, PBP2c, APH(3')-III, ANT(4')-I, and AAC(6')-APH(2''), directly from positive blood cultures and in less than 70 min including a 30-min cefoxitin-induction step. The method was tested on spiked blood culture bottles inoculated with 124 S.aureus, accounting for the known genomic diversity of SCCmec types and the genetic background of the strains. RESULTS This method provided 99% agreement for PBP2a (n = 98/99 strains) detection. Agreement was 100% for PBP2c (n = 5/5), APH(3')-III (n = 16/16), and ANT(4')-I (n = 20/20), and 94% for AAC(6')-APH(2'') (n = 16/17). Across the entire strain collection, 100% negative agreement was reported for each of the 5 resistance proteins. Additionally, relative quantification of ANT(4')-I expression allowed to discriminate kanamycin-susceptible and -resistant strains, in all strains harbouring the ant(4')-Ia gene. CONCLUSION The LC-MS/MS method presented herein demonstrates its ability to provide a reliable determination of S. aureus resistance mechanisms, directly from positive blood cultures and in a short turnaround time, as required in clinical laboratories.
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Affiliation(s)
- Francis Deforet
- Institut des Sciences Analytiques, Université de Lyon, Université Claude Bernard Lyon 1, Centre National de la Recherche Scientifique (CNRS), UMR 5280, Villeurbanne, France
| | - Romain Carrière
- Institut des Sciences Analytiques, Université de Lyon, Université Claude Bernard Lyon 1, Centre National de la Recherche Scientifique (CNRS), UMR 5280, Villeurbanne, France
| | - Pierre L 'Aour Dufour
- Institut des Sciences Analytiques, Université de Lyon, Université Claude Bernard Lyon 1, Centre National de la Recherche Scientifique (CNRS), UMR 5280, Villeurbanne, France
- Hospices Civils de Lyon, Institut des Agents Infectieux, Lyon, France
| | - Roxane Prat
- Hospices Civils de Lyon, Institut des Agents Infectieux, Lyon, France
| | - Chloé Desbiolles
- Hospices Civils de Lyon, Institut des Agents Infectieux, Lyon, France
| | - Noémie Cottin
- Hospices Civils de Lyon, Institut des Agents Infectieux, Lyon, France
| | - Alicia Reuzeau
- Hospices Civils de Lyon, Institut des Agents Infectieux, Lyon, France
| | - Olivier Dauwalder
- Hospices Civils de Lyon, Institut des Agents Infectieux, Lyon, France
| | - Céline Dupieux-Chabert
- Centre National de Référence des Staphylocoques, Institut des agents infectieux, Hospices Civils de Lyon, Lyon, France
| | - Anne Tristan
- Centre National de Référence des Staphylocoques, Institut des agents infectieux, Hospices Civils de Lyon, Lyon, France
- CIRI, Centre International de Recherche en Infectiologie, Université de Lyon, Inserm, U1111, Université Claude Bernard Lyon 1, Centre National de la Recherche Scientifique (CNRS), UMR5308, École Normale Supérieure (ENS) de Lyon, Lyon, France
| | - Tiphaine Cecchini
- Hospices Civils de Lyon, Institut des Agents Infectieux, Lyon, France
| | - Jérôme Lemoine
- Institut des Sciences Analytiques, Université de Lyon, Université Claude Bernard Lyon 1, Centre National de la Recherche Scientifique (CNRS), UMR 5280, Villeurbanne, France
| | - François Vandenesch
- Hospices Civils de Lyon, Institut des Agents Infectieux, Lyon, France.
- Centre National de Référence des Staphylocoques, Institut des agents infectieux, Hospices Civils de Lyon, Lyon, France.
- CIRI, Centre International de Recherche en Infectiologie, Université de Lyon, Inserm, U1111, Université Claude Bernard Lyon 1, Centre National de la Recherche Scientifique (CNRS), UMR5308, École Normale Supérieure (ENS) de Lyon, Lyon, France.
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2
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Weig AW, O'Conner PM, Kwiecinski JM, Marciano OM, Nunag A, Gutierrez AT, Melander RJ, Horswill AR, Melander C. A structure activity relationship study of 3,4'-dimethoxyflavone for ArlRS inhibition in Staphylococcus aureus. Org Biomol Chem 2023; 21:3373-3380. [PMID: 37013457 PMCID: PMC10192164 DOI: 10.1039/d3ob00123g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/31/2023]
Abstract
Infections caused by methicillin-resistant Staphylococcus aureus (MRSA) are difficult to treat due to their resistance to many β-lactam antibiotics, and their highly coordinated excretion of virulence factors. One way in which MRSA accomplishes this is by responding to environmental stimuli using two-component systems (TCS). The ArlRS TCS has been identified as having a key role in regulating virulence in both systemic and local infections caused by S. aureus. We recently disclosed 3,4'-dimethoxyflavone as a selective ArlRS inhibitor. In this study we explore the structure-activity relationship (SAR) of the flavone scaffold for ArlRS inhibition and identify several compounds with increased activity compared to the parent. Additionally, we identify a compound that suppresses oxacillin resistance in MRSA, and begin to probe the mechanism of action behind this activity.
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Affiliation(s)
- Alexander W Weig
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA.
| | - Patrick M O'Conner
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA.
| | - Jakub M Kwiecinski
- Department of Immunology and Microbiology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA.
| | - Orry M Marciano
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA.
| | - Angelica Nunag
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA.
| | - Andrew T Gutierrez
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA.
| | - Roberta J Melander
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA.
| | - Alexander R Horswill
- Department of Immunology and Microbiology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA.
| | - Christian Melander
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA.
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3
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Fisher JF, Mobashery S. β-Lactams against the Fortress of the Gram-Positive Staphylococcus aureus Bacterium. Chem Rev 2021; 121:3412-3463. [PMID: 33373523 PMCID: PMC8653850 DOI: 10.1021/acs.chemrev.0c01010] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The biological diversity of the unicellular bacteria-whether assessed by shape, food, metabolism, or ecological niche-surely rivals (if not exceeds) that of the multicellular eukaryotes. The relationship between bacteria whose ecological niche is the eukaryote, and the eukaryote, is often symbiosis or stasis. Some bacteria, however, seek advantage in this relationship. One of the most successful-to the disadvantage of the eukaryote-is the small (less than 1 μm diameter) and nearly spherical Staphylococcus aureus bacterium. For decades, successful clinical control of its infection has been accomplished using β-lactam antibiotics such as the penicillins and the cephalosporins. Over these same decades S. aureus has perfected resistance mechanisms against these antibiotics, which are then countered by new generations of β-lactam structure. This review addresses the current breadth of biochemical and microbiological efforts to preserve the future of the β-lactam antibiotics through a better understanding of how S. aureus protects the enzyme targets of the β-lactams, the penicillin-binding proteins. The penicillin-binding proteins are essential enzyme catalysts for the biosynthesis of the cell wall, and understanding how this cell wall is integrated into the protective cell envelope of the bacterium may identify new antibacterials and new adjuvants that preserve the efficacy of the β-lactams.
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Affiliation(s)
- Jed F Fisher
- Department of Chemistry and Biochemistry, McCourtney Hall, University of Notre Dame, Notre Dame Indiana 46556, United States
| | - Shahriar Mobashery
- Department of Chemistry and Biochemistry, McCourtney Hall, University of Notre Dame, Notre Dame Indiana 46556, United States
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4
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Fisher JF, Mobashery S. Constructing and deconstructing the bacterial cell wall. Protein Sci 2020; 29:629-646. [PMID: 31747090 PMCID: PMC7021008 DOI: 10.1002/pro.3737] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Revised: 09/17/2019] [Accepted: 09/18/2019] [Indexed: 12/11/2022]
Abstract
The history of modern medicine cannot be written apart from the history of the antibiotics. Antibiotics are cytotoxic secondary metabolites that are isolated from Nature. The antibacterial antibiotics disproportionately target bacterial protein structure that is distinct from eukaryotic protein structure, notably within the ribosome and within the pathways for bacterial cell-wall biosynthesis (for which there is not a eukaryotic counterpart). This review focuses on a pre-eminent class of antibiotics-the β-lactams, exemplified by the penicillins and cephalosporins-from the perspective of the evolving mechanisms for bacterial resistance. The mechanism of action of the β-lactams is bacterial cell-wall destruction. In the monoderm (single membrane, Gram-positive staining) pathogen Staphylococcus aureus the dominant resistance mechanism is expression of a β-lactam-unreactive transpeptidase enzyme that functions in cell-wall construction. In the diderm (dual membrane, Gram-negative staining) pathogen Pseudomonas aeruginosa a dominant resistance mechanism (among several) is expression of a hydrolytic enzyme that destroys the critical β-lactam ring of the antibiotic. The key sensing mechanism used by P. aeruginosa is monitoring the molecular difference between cell-wall construction and cell-wall deconstruction. In both bacteria, the resistance pathways are manifested only when the bacteria detect the presence of β-lactams. This review summarizes how the β-lactams are sensed and how the resistance mechanisms are manifested, with the expectation that preventing these processes will be critical to future chemotherapeutic control of multidrug resistant bacteria.
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Affiliation(s)
- Jed F. Fisher
- Department of Chemistry and BiochemistryUniversity of Notre DameSouth BendIndiana
| | - Shahriar Mobashery
- Department of Chemistry and BiochemistryUniversity of Notre DameSouth BendIndiana
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5
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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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6
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Ferreira M, Bernardo L, Neves L, Campos M, Lamaro-Cardoso J, André M. Virulence profile and genetic variability of Staphylococcus aureus isolated from artisanal cheese. J Dairy Sci 2016; 99:8589-8597. [DOI: 10.3168/jds.2015-10732] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 02/29/2016] [Indexed: 11/19/2022]
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7
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Staude MW, Frederick TE, Natarajan SV, Wilson BD, Tanner CE, Ruggiero ST, Mobashery S, Peng JW. Investigation of signal transduction routes within the sensor/transducer protein BlaR1 of Staphylococcus aureus. Biochemistry 2015; 54:1600-10. [PMID: 25658195 DOI: 10.1021/bi501463k] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The transmembrane antibiotic sensor/signal transducer protein BlaR1 is part of a cohort of proteins that confer β-lactam antibiotic resistance in methicillin-resistant Staphylococcus aureus (MRSA) [Fisher, J. F., Meroueh, S. O., and Mobashery, S. (2005) Chem. Rev. 105, 395-424; Llarrull, L. I., Fisher, J. F., and Mobashery, S. (2009) Antimicrob. Agents Chemother. 53, 4051-4063; Llarrull, L. I., Toth, M., Champion, M. M., and Mobashery, S. (2011) J. Biol. Chem. 286, 38148-38158]. Specifically, BlaR1 regulates the inducible expression of β-lactamases that hydrolytically destroy β-lactam antibiotics. The resistance phenotype starts with β-lactam antibiotic acylation of the BlaR1 extracellular domain (BlaRS). The acylation activates the cytoplasmic protease domain through an obscure signal transduction mechanism. Here, we compare protein dynamics of apo versus antibiotic-acylated BlaRS using nuclear magnetic resonance. Our analyses reveal inter-residue interactions that relay acylation-induced perturbations within the antibiotic-binding site to the transmembrane helix regions near the membrane surface. These are the first insights into the process of signal transduction by BlaR1.
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Affiliation(s)
- Michael W Staude
- Department of Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556, United States
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8
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Fishovitz J, Hermoso JA, Chang M, Mobashery S. Penicillin-binding protein 2a of methicillin-resistant Staphylococcus aureus. IUBMB Life 2014; 66:572-7. [PMID: 25044998 DOI: 10.1002/iub.1289] [Citation(s) in RCA: 147] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2014] [Accepted: 06/01/2014] [Indexed: 01/31/2023]
Abstract
High-level resistance to β-lactam antibiotics in methicillin-resistant Staphylococcus aureus (MRSA) is due to expression of penicillin-binding protein 2a (PBP2a), a transpeptidase that catalyzes cell-wall crosslinking in the face of the challenge by β-lactam antibiotics. The activity of this protein is regulated by allostery at a site 60 Å distant from the active site, where crosslinking of cell wall takes place. This review discusses the state of knowledge on this important enzyme of cell-wall biosynthesis in MRSA.
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Affiliation(s)
- Jennifer Fishovitz
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, USA
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9
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Blázquez B, Llarrull LI, Luque-Ortega JR, Alfonso C, Boggess B, Mobashery S. Regulation of the expression of the β-lactam antibiotic-resistance determinants in methicillin-resistant Staphylococcus aureus (MRSA). Biochemistry 2014; 53:1548-50. [PMID: 24564530 PMCID: PMC3971960 DOI: 10.1021/bi500074w] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
![]()
β-Lactam
antibiotics have faced obsolescence with the emergence
of methicillin-resistant Staphylococcus aureus (MRSA).
A complex set of events ensues upon exposure of MRSA to these antibiotics,
which culminates in proteolysis of BlaI or MecI, two gene repressors,
and results in the induction of resistance. We report studies on the
mechanism of binding of these gene repressors to the operator regions
by fluorescence anisotropy. Within the range of in vivo concentrations for BlaI and MecI, these proteins interact with their
regulatory elements in a reversible manner, as both a monomer and
a dimer.
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Affiliation(s)
- Blas Blázquez
- Department Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556, United States
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10
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Arêde P, Botelho T, Guevara T, Usón I, Oliveira DC, Gomis-Rüth FX. Structure-function studies of the staphylococcal methicillin resistance antirepressor MecR2. J Biol Chem 2013; 288:21267-21278. [PMID: 23733184 DOI: 10.1074/jbc.m112.448134] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Methicillin resistance in Staphylococcus aureus is elicited by the MecI-MecR1-MecA axis encoded by the mec locus. Recently, MecR2 was also identified as a regulator of mec through binding of the methicillin repressor, MecI. Here we show that plasmid-encoded full-length MecR2 restores resistance in a sensitive S. aureus mecR2 deletion mutant of the resistant strain N315. The crystal structure of MecR2 reveals an N-terminal DNA-binding domain, an intermediate scaffold domain, and a C-terminal dimerization domain that contributes to oligomerization. The protein shows structural similarity to ROK (repressors, open reading frames, and kinases) family proteins, which bind DNA and/or sugar molecules. We found that functional cell-based assays of three point mutants affecting residues participating in sugar binding in ROK proteins had no effect on the resistance phenotype. By contrast, MecR2 bound short double-stranded DNA oligonucleotides nonspecifically, and a deletion mutant affecting the N-terminal DNA-binding domain showed a certain effect on activity, thus contributing to resistance less than the wild-type protein. Similarly, a deletion mutant, in which a flexible segment of intermediate scaffold domain had been replaced by four glycines, significantly reduced MecR2 function, thus indicating that this domain may likewise be required for activity. Taken together, these results provide the structural basis for the activity of a methicillin antirepressor, MecR2, which would sequester MecI away from its cognate promoter region and facilitate its degradation.
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Affiliation(s)
- Pedro Arêde
- the Center for Microbiological Resources, Department of Life Sciences, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Quinta da Torre, P-2829-516 Caparica, Portugal, and
| | - Tiago Botelho
- From the Proteolysis Lab, Department of Structural Biology, Molecular Biology Institute of Barcelona, CSIC, E-08028 Barcelona, Catalonia, Spain
| | - Tibisay Guevara
- From the Proteolysis Lab, Department of Structural Biology, Molecular Biology Institute of Barcelona, CSIC, E-08028 Barcelona, Catalonia, Spain
| | - Isabel Usón
- the Institució Catalana de Recerca i Estudis Avançats, Molecular Biology Institute of Barcelona, CSIC, Barcelona Science Park, E-08028 Barcelona, Catalonia, Spain
| | - Duarte C Oliveira
- the Center for Microbiological Resources, Department of Life Sciences, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Quinta da Torre, P-2829-516 Caparica, Portugal, and
| | - F Xavier Gomis-Rüth
- From the Proteolysis Lab, Department of Structural Biology, Molecular Biology Institute of Barcelona, CSIC, E-08028 Barcelona, Catalonia, Spain,.
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11
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Abstract
Many Gram-negative and Gram-positive bacteria recycle a significant proportion of the peptidoglycan components of their cell walls during their growth and septation. In many--and quite possibly all--bacteria, the peptidoglycan fragments are recovered and recycled. Although cell-wall recycling is beneficial for the recovery of resources, it also serves as a mechanism to detect cell-wall-targeting antibiotics and to regulate resistance mechanisms. In several Gram-negative pathogens, anhydro-MurNAc-peptide cell-wall fragments regulate AmpC β-lactamase induction. In some Gram-positive organisms, short peptides derived from the cell wall regulate the induction of both β-lactamase and β-lactam-resistant penicillin-binding proteins. The involvement of peptidoglycan recycling with resistance regulation suggests that inhibitors of the enzymes involved in the recycling might synergize with cell-wall-targeted antibiotics. Indeed, such inhibitors improve the potency of β-lactams in vitro against inducible AmpC β-lactamase-producing bacteria. We describe the key steps of cell-wall remodeling and recycling, the regulation of resistance mechanisms by cell-wall recycling, and recent advances toward the discovery of cell-wall-recycling inhibitors.
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Affiliation(s)
- Jarrod W Johnson
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, USA
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12
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Buchman JS, Schneider KD, Lloyd AR, Pavlish SL, Leonard DA. Site-saturation mutagenesis of position V117 in OXA-1 β-lactamase: effect of side chain polarity on enzyme carboxylation and substrate turnover. Biochemistry 2012; 51:3143-50. [PMID: 22429123 DOI: 10.1021/bi201896k] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Class D β-lactamases pose an emerging threat to the efficacy of β-lactam therapy for bacterial infections. Class D enzymes differ mechanistically from other β-lactamases by the presence of an active-site N-carboxylated lysine that serves as a general base to activate the serine nucleophile for attack. We have used site-saturation mutagenesis at position V117 in the class D β-lactamase OXA-1 to investigate how alterations in the environment around N-carboxylated K70 affect the ability of that modified residue to carry out its normal function. Minimum inhibitory concentration analysis of the 20 position 117 variants demonstrates a clear pattern of charge and polarity effects on the level of ampicillin resistance imparted on Escherichia coli (E. coli). Substitutions that introduce a negative charge (D, E) at position 117 reduce resistance to near background levels, while the positively charged K and R residues maintain the highest resistance levels of all mutants. Treatment of the acidic variants with the fluorescent penicillin BOCILLIN FL followed by SDS-PAGE shows that they are active for acylation by substrate but deacylation-deficient. We used a novel fluorescence anisotropy assay to show that the specific charge and hydrogen-bonding potential of the residue at position 117 affect CO(2) binding to K70, which in turn correlates to deacylation activity. These conclusions are discussed in light of the mechanisms proposed for both class D β-lactamases and BlaR β-lactam sensor proteins and suggest a reason for the preponderance of asparagine at the V117-homologous position in the sensors.
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Affiliation(s)
- Jennifer S Buchman
- Department of Chemistry, Grand Valley State University, Allendale, Michigan 49401, USA
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13
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Black CC, Eberlein LC, Solyman SM, Wilkes RP, Hartmann FA, Rohrbach BW, Bemis DA, Kania SA. The role of mecA and blaZ regulatory elements in mecA expression by regional clones of methicillin-resistant Staphylococcus pseudintermedius. Vet Microbiol 2011; 151:345-53. [PMID: 21514752 DOI: 10.1016/j.vetmic.2011.03.026] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2011] [Revised: 03/03/2011] [Accepted: 03/23/2011] [Indexed: 11/28/2022]
Abstract
Two major regional clones of methicillin-resistant Staphylococcus pseudintermedius (MRSP) have been identified in Europe and North America. They are designated multilocus sequence types (ST) 71 and 68 and contain staphylococcal chromosome cassette (SCCmec) types II-III and V(T), respectively. One notable difference between the two clones is a deletion in the mecI/mecR1 regulatory apparatus of ST 68 SCCmec V(T). This deletion in analogous methicillin-resistant Staphylococcus aureus (MRSA) results in more responsive and greater expression of the mecA encoded penicillin-binding protein 2a, and is associated with SCCmec types occurring in community-acquired MRSA lineages. The aim of this study was to characterize mec and bla regulatory apparatuses in MRSP and determine their effects on expression of mecA. Seventeen S. pseudintermedius isolates representing nine methicillin-resistant ST lineages were screened for the presence of the repressors blaI and mecI and sensors blaR1 and mecR1. The bla and mec operons for each isolate were sequenced and compared for homology between the repressor open-reading frames (ORF), sensor ORFs, and mecA promoter regions. A real-time reverse transcriptase PCR expression assay was developed, validated and applied to nine isolates determining the effect of oxacillin induction on mecA transcription. Significant differences were found in mecA expression between isolates with a full regulatory complement (mecI/mecR1 and blaI/blaR1) and those with truncated and/or absent regulatory elements. Isolates representative of European and North American MRSP ST regional clones have dissimilar mecA responses to oxacillin.
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Affiliation(s)
- C C Black
- Department of Comparative Medicine, College of Veterinary Medicine, University of Tennessee, 2407 River Drive, Knoxville, TN 37996, United States
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14
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Three factors that modulate the activity of class D β-lactamases and interfere with the post-translational carboxylation of Lys70. Biochem J 2011; 432:495-504. [PMID: 21108605 DOI: 10.1042/bj20101122] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The activity of class D β-lactamases is dependent on Lys70 carboxylation in the active site. Structural, kinetic and affinity studies show that this post-translational modification can be affected by the presence of a poor substrate such as moxalactam but also by the V117T substitution. Val117 is a strictly conserved hydrophobic residue located in the active site. In addition, inhibition of class D β-lactamases by chloride ions is due to a competition between the side chain carboxylate of the modified Lys70 and chloride ions. Determination of the individual kinetic constants shows that the deacylation of the acyl-enzyme is the rate-limiting step for the wild-type OXA-10 β-lactamase.
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Li Y, Yu X, Ho J, Fushman D, Allewell NM, Tuchman M, Shi D. Reversible post-translational carboxylation modulates the enzymatic activity of N-acetyl-L-ornithine transcarbamylase. Biochemistry 2010; 49:6887-95. [PMID: 20695527 DOI: 10.1021/bi1007386] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
N-Acetyl-l-ornithine transcarbamylase (AOTCase), rather than ornithine transcarbamylase (OTCase), is the essential carbamylase enzyme in the arginine biosynthesis of several plant and human pathogens. The specificity of this unique enzyme provides a potential target for controlling the spread of these pathogens. Recently, several crystal structures of AOTCase from Xanthomonas campestris (xc) have been determined. In these structures, an unexplained electron density at the tip of the Lys302 side chain was observed. Using (13)C NMR spectroscopy, we show herein that Lys302 is post-translationally carboxylated. The structure of wild-type AOTCase in a complex with the bisubstrate analogue N(delta)-(phosphonoacetyl)-N(alpha)-acetyl-l-ornithine (PALAO) indicates that the carboxyl group on Lys302 forms a strong hydrogen bonding network with surrounding active site residues, Lys252, Ser253, His293, and Glu92 from the adjacent subunit either directly or via a water molecule. Furthermore, the carboxyl group is involved in binding N-acetyl-l-ornithine via a water molecule. Activity assays with the wild-type enzyme and several mutants demonstrate that the post-translational modification of lysine 302 has an important role in catalysis.
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Affiliation(s)
- Yongdong Li
- Research Center for Genetic Medicine and Department of Integrative Systems Biology, Children's National Medical Center, The George Washington University, Washington, DC 20010, USA
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McCallum N, Berger-Bächi B, Senn MM. Regulation of antibiotic resistance in Staphylococcus aureus. Int J Med Microbiol 2009; 300:118-29. [PMID: 19800843 DOI: 10.1016/j.ijmm.2009.08.015] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
Staphylococcus aureus has a formidable ability to adapt to varying environmental conditions and an extraordinary capacity to rapidly become resistant to virtually all antibiotics. Resistance develops either through mutations and rearrangements within the staphylococcal genome, or by the acquisition of resistance determinants. Antibiotic resistances often impose a fitness burden on the host. Such biological costs can be reduced by tight regulation and antibiotic-inducible expression of resistance genes, or by compensatory mutations. Resistance induction by antibiotics can be mediated by dedicated, antibiotic-recognizing signal transducers or by mechanisms relieving translational attenuation. Antibiotic tolerance and the expression of resistance phenotypes can also be strongly influenced by the genetic backgrounds of strains and several other factors. Modification and indirect regulation of resistance levels can occur by mutations that alter gene expression or substrate specificity of genes contributing to resistance. Insertion elements can alter resistance profiles by turning relevant genes on or off. Environmental conditions and stress response mechanisms triggered by perturbation of the cell envelope, DNA damage, or faulty intermediary metabolism can also have an impact on resistance development and expression. Clinically relevant resistance is often built up through multiple steps, each of which contributes to an increase in resistance. The driving force behind resistance formation is antibiotic stress, and under clinical conditions selection for resistance is continuously competing with selection for bacterial fitness.
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Affiliation(s)
- Nadine McCallum
- Institute of Medical Microbiology, University of Zürich, Gloriastrasse 32, CH-8006 Zürich, Switzerland
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Staub I, Sieber SA. Beta-lactam probes as selective chemical-proteomic tools for the identification and functional characterization of resistance associated enzymes in MRSA. J Am Chem Soc 2009; 131:6271-6. [PMID: 19354235 DOI: 10.1021/ja901304n] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
With the development of antibiotic resistant bacterial strains, infectious diseases have become again a life threatening problem. One of the reasons for this dilemma is the limited number and breadth of current therapeutic targets for which several resistance strategies have evolved over time. To identify resistance associated targets and to understand their function, activity, and regulation, we utilized a novel strategy based on small synthetic beta-lactam molecules that were applied in activity based protein profiling experiments (ABPP) to comparatively profile in situ enzyme activities in antibiotic sensitive and resistant S. aureus strains (MRSA). Several enzyme activities which are unique to the MRSA strain including known resistant associated targets, involved in cell wall biosynthesis and antibiotic sensing, could be identified. In addition, we also identified uncharacterized enzymes which turned out to be capable of hydrolyzing beta-lactam antibiotics. This technology could therefore represent a valuable tool to monitor the activity and function of other yet unexplored resistance associated enzymes in pathogenic bacteria and help to discover new drug targets for customized therapeutic interventions.
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Affiliation(s)
- Isabell Staub
- Center for Integrated Protein Science Munich CIPSM, Department of Chemistry and Biochemistry, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, 81377 Munich, Germany
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Molecular basis and phenotype of methicillin resistance in Staphylococcus aureus and insights into new beta-lactams that meet the challenge. Antimicrob Agents Chemother 2009; 53:4051-63. [PMID: 19470504 DOI: 10.1128/aac.00084-09] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
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The role of OXA-1 beta-lactamase Asp(66) in the stabilization of the active-site carbamate group and in substrate turnover. Biochem J 2008; 410:455-62. [PMID: 18031291 DOI: 10.1042/bj20070573] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The OXA-1 beta-lactamase is one of the few class D enzymes that has an aspartate residue at position 66, a position that is proximal to the active-site residue Ser(67). In class A beta-lactamases, such as TEM-1 and SHV-1, residues adjacent to the active-site serine residue play a crucial role in inhibitor resistance and substrate selectivity. To probe the role of Asp(66) in substrate affinity and catalysis, we performed site-saturation mutagenesis at this position. Ampicillin MIC (minimum inhibitory concentration) values for the full set of Asp(66) mutants expressed in Escherichia coli DH10B ranged from < or =8 microg/ml for cysteine, proline and the basic amino acids to > or =256 microg/ml for asparagine, leucine and the wild-type aspartate. Replacement of aspartic acid by asparagine at position 66 also led to a moderate enhancement of extended-spectrum cephalosporin resistance. OXA-1 shares with other class D enzymes a carboxylated residue, Lys(70), that acts as a general base in the catalytic mechanism. The addition of 25 mM bicarbonate to Luria-Bertani-broth agar resulted in a > or =16-fold increase in MICs for most OXA-1 variants with amino acid replacements at position 66 when expressed in E. coli. Because Asp(66) forms hydrogen bonds with several other residues in the OXA-1 active site, we propose that this residue plays a role in stabilizing the CO2 bound to Lys(70) and thereby profoundly affects substrate turnover.
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