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López-Argüello S, Montaner M, Sayed ARM, Oliver A, Bulitta JB, Moya B. Penicillin-Binding Protein 5/6 Acting as a Decoy Target in Pseudomonas aeruginosa Identified by Whole-Cell Receptor Binding and Quantitative Systems Pharmacology. Antimicrob Agents Chemother 2023; 67:e0160322. [PMID: 37199612 PMCID: PMC10269149 DOI: 10.1128/aac.01603-22] [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: 11/30/2022] [Accepted: 04/23/2023] [Indexed: 05/19/2023] Open
Abstract
The β-lactam antibiotics have been successfully used for decades to combat susceptible Pseudomonas aeruginosa, which has a notoriously difficult to penetrate outer membrane (OM). However, there is a dearth of data on target site penetration and covalent binding of penicillin-binding proteins (PBP) for β-lactams and β-lactamase inhibitors in intact bacteria. We aimed to determine the time course of PBP binding in intact and lysed cells and estimate the target site penetration and PBP access for 15 compounds in P. aeruginosa PAO1. All β-lactams (at 2 × MIC) considerably bound PBPs 1 to 4 in lysed bacteria. However, PBP binding in intact bacteria was substantially attenuated for slow but not for rapid penetrating β-lactams. Imipenem yielded 1.5 ± 0.11 log10 killing at 1h compared to <0.5 log10 killing for all other drugs. Relative to imipenem, the rate of net influx and PBP access was ~ 2-fold slower for doripenem and meropenem, 7.6-fold for avibactam, 14-fold for ceftazidime, 45-fold for cefepime, 50-fold for sulbactam, 72-fold for ertapenem, ~ 249-fold for piperacillin and aztreonam, 358-fold for tazobactam, ~547-fold for carbenicillin and ticarcillin, and 1,019-fold for cefoxitin. At 2 × MIC, the extent of PBP5/6 binding was highly correlated (r2 = 0.96) with the rate of net influx and PBP access, suggesting that PBP5/6 acted as a decoy target that should be avoided by slowly penetrating, future β-lactams. This first comprehensive assessment of the time course of PBP binding in intact and lysed P. aeruginosa explained why only imipenem killed rapidly. The developed novel covalent binding assay in intact bacteria accounts for all expressed resistance mechanisms.
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Affiliation(s)
- Silvia López-Argüello
- Servicio de Microbiología and Unidad de Investigación, Hospital Universitario Son Espases, Instituto de Investigación Sanitaria Illes Balears (IdISBa), Palma de Mallorca, Spain
| | - Maria Montaner
- Servicio de Microbiología and Unidad de Investigación, Hospital Universitario Son Espases, Instituto de Investigación Sanitaria Illes Balears (IdISBa), Palma de Mallorca, Spain
| | - Alaa RM. Sayed
- Department of Pharmacotherapy and Translational Research, College of Pharmacy, University of Florida, Orlando, Florida, USA
- Department of Chemistry, Faculty of Science, Fayoum University, Fayoum, Egypt
| | - Antonio Oliver
- Servicio de Microbiología and Unidad de Investigación, Hospital Universitario Son Espases, Instituto de Investigación Sanitaria Illes Balears (IdISBa), Palma de Mallorca, Spain
| | - Jürgen B. Bulitta
- Department of Pharmacotherapy and Translational Research, College of Pharmacy, University of Florida, Orlando, Florida, USA
| | - Bartolome Moya
- Servicio de Microbiología and Unidad de Investigación, Hospital Universitario Son Espases, Instituto de Investigación Sanitaria Illes Balears (IdISBa), Palma de Mallorca, Spain
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Sabzehali F, Rahimi H, Goudarzi H, Goudarzi M, Yoosefi Izad MH, Salimi Chirani A, Jalali SA, Faghihloo E. Functional engineering of OprF-OprI-PopB as a chimeric immunogen and its cross-protective evaluation with GM-CSF against Pseudomonas aeruginosa: A comprehensive immunoinformatics evaluation. INFORMATICS IN MEDICINE UNLOCKED 2021. [DOI: 10.1016/j.imu.2021.100673] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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Ulloa ER, Dillon N, Tsunemoto H, Pogliano J, Sakoulas G, Nizet V. Avibactam Sensitizes Carbapenem-Resistant NDM-1-Producing Klebsiella pneumoniae to Innate Immune Clearance. J Infect Dis 2020; 220:484-493. [PMID: 30923801 PMCID: PMC6603980 DOI: 10.1093/infdis/jiz128] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Accepted: 04/05/2019] [Indexed: 11/16/2022] Open
Abstract
Infections caused by New Delhi metallo-β-lactamase (NDM)–producing strains of multidrug-resistant Klebsiella pneumoniae are a global public health threat lacking reliable therapies. NDM is impervious to all existing β-lactamase inhibitor (BLI) drugs, including the non–β-lactam BLI avibactam (AVI). Though lacking direct activity against NDMs, AVI can interact with penicillin-binding protein 2 in a manner that may influence cell wall dynamics. We found that exposure of NDM-1–producing K. pneumoniae to AVI led to striking bactericidal interactions with human cathelicidin antimicrobial peptide LL-37, a frontline component of host innate immunity. Moreover, AVI markedly sensitized NDM-1–producing K. pneumoniae to killing by freshly isolated human neutrophils, platelets, and serum when complement was active. Finally, AVI monotherapy reduced lung counts of NDM-1–producing K. pneumoniae in a murine pulmonary challenge model. AVI sensitizes NDM-1–producing K. pneumoniae to innate immune clearance in ways that are not appreciated by standard antibiotic testing and that merit further study.
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Affiliation(s)
- Erlinda R Ulloa
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, La Jolla.,Division of Infectious Disease, Department of Pediatrics, Children's Hospital of Philadelphia, Pennsylvania
| | - Nicholas Dillon
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, La Jolla
| | - Hannah Tsunemoto
- Division of Biological Sciences, University of California-San Diego, La Jolla
| | - Joe Pogliano
- Division of Biological Sciences, University of California-San Diego, La Jolla
| | - George Sakoulas
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, La Jolla.,Sharp Healthcare System, San Diego, California
| | - Victor Nizet
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, La Jolla.,Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California-San Diego, La Jolla
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Anderson EM, Sychantha D, Brewer D, Clarke AJ, Geddes-McAlister J, Khursigara CM. Peptidoglycomics reveals compositional changes in peptidoglycan between biofilm- and planktonic-derived Pseudomonas aeruginosa. J Biol Chem 2019; 295:504-516. [PMID: 31771981 DOI: 10.1074/jbc.ra119.010505] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Revised: 11/25/2019] [Indexed: 12/14/2022] Open
Abstract
Peptidoglycan (PG) is a critical component of the bacterial cell wall and is composed of a repeating β-1,4-linked disaccharide of N-acetylglucosamine and N-acetylmuramic acid appended with a highly conserved stem peptide. In Gram-negative bacteria, PG is assembled in the cytoplasm and exported into the periplasm where it undergoes considerable maturation, modification, or degradation depending on the growth phase or presence of environmental stressors. These modifications serve important functions in diverse processes, including PG turnover, cell elongation/division, and antibiotic resistance. Conventional methods for analyzing PG composition are complex and time-consuming. We present here a streamlined MS-based method that combines differential analysis with statistical 1D annotation approaches to quantitatively compare PGs produced in planktonic- and biofilm-cultured Pseudomonas aeruginosa We identified a core assembly of PG that is present in high abundance and that does not significantly differ between the two growth states. We also identified an adaptive PG assembly that is present in smaller amounts and fluctuates considerably between growth states in response to physiological changes. Biofilm-derived adaptive PG exhibited significant changes compared with planktonic-derived PG, including amino acid substitutions of the stem peptide and modifications that indicate changes in the activity of amidases, deacetylases, and lytic transglycosylases. The results of this work also provide first evidence of de-N-acetylated muropeptides from P. aeruginosa The method developed here offers a robust and reproducible workflow for accurately determining PG composition in samples that can be used to assess global PG fluctuations in response to changing growth conditions or external stimuli.
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Affiliation(s)
- Erin M Anderson
- Department of Molecular and Cellular Biology, University of Guelph, Ontario N1G 2W1, Canada
| | - David Sychantha
- Department of Molecular and Cellular Biology, University of Guelph, Ontario N1G 2W1, Canada
| | - Dyanne Brewer
- Mass Spectrometry Facility, University of Guelph, Ontario N1G 2W1, Canada
| | - Anthony J Clarke
- Department of Molecular and Cellular Biology, University of Guelph, Ontario N1G 2W1, Canada
| | - Jennifer Geddes-McAlister
- Department of Molecular and Cellular Biology, University of Guelph, Ontario N1G 2W1, Canada; Mass Spectrometry Facility, University of Guelph, Ontario N1G 2W1, Canada.
| | - Cezar M Khursigara
- Department of Molecular and Cellular Biology, University of Guelph, Ontario N1G 2W1, Canada; Mass Spectrometry Facility, University of Guelph, Ontario N1G 2W1, Canada.
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In Vitro Activity of Tebipenem (SPR859) against Penicillin-Binding Proteins of Gram-Negative and Gram-Positive Bacteria. Antimicrob Agents Chemother 2019; 63:AAC.02181-18. [PMID: 30718255 DOI: 10.1128/aac.02181-18] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Accepted: 01/29/2019] [Indexed: 12/25/2022] Open
Abstract
Tebipenem (SPR859) is the microbiologically active form of SPR994 (tebipenem-pivoxil), an orally available carbapenem with activity against extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae Measurement of the relative binding of SPR859 to the bacterial cell targets revealed that it is a potent inhibitor of multiple penicillin-binding proteins (PBPs) but primarily a Gram-negative PBP 2 inhibitor, similar to other compounds in this class. These data support further clinical development of SPR994.
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Geisinger E, Mortman NJ, Vargas-Cuebas G, Tai AK, Isberg RR. A global regulatory system links virulence and antibiotic resistance to envelope homeostasis in Acinetobacter baumannii. PLoS Pathog 2018; 14:e1007030. [PMID: 29795704 PMCID: PMC5967708 DOI: 10.1371/journal.ppat.1007030] [Citation(s) in RCA: 68] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Accepted: 04/16/2018] [Indexed: 11/19/2022] Open
Abstract
The nosocomial pathogen Acinetobacter baumannii is a significant threat due to its ability to cause infections refractory to a broad range of antibiotic treatments. We show here that a highly conserved sensory-transduction system, BfmRS, mediates the coordinate development of both enhanced virulence and resistance in this microorganism. Hyperactive alleles of BfmRS conferred increased protection from serum complement killing and allowed lethal systemic disease in mice. BfmRS also augmented resistance and tolerance against an expansive set of antibiotics, including dramatic protection from β-lactam toxicity. Through transcriptome profiling, we showed that BfmRS governs these phenotypes through global transcriptional regulation of a post-exponential-phase-like program of gene expression, a key feature of which is modulation of envelope biogenesis and defense pathways. BfmRS activity defended against cell-wall lesions through both β-lactamase-dependent and -independent mechanisms, with the latter being connected to control of lytic transglycosylase production and proper coordination of morphogenesis and division. In addition, hypersensitivity of bfmRS knockouts could be suppressed by unlinked mutations restoring a short, rod cell morphology, indicating that regulation of drug resistance, pathogenicity, and envelope morphogenesis are intimately linked by this central regulatory system in A. baumannii. This work demonstrates that BfmRS controls a global regulatory network coupling cellular physiology to the ability to cause invasive, drug-resistant infections. Infections with the hospital-acquired bacterium Acinetobacter baumannii are highly difficult to treat. The pathogen has evolved multiple lines of defense against antimicrobial stress, including a barrier-forming cell envelope as well as control systems that respond to antimicrobial stresses by enhancing antibiotic resistance and virulence. Here, we uncovered the role of a key stress-response system, BfmRS, in controlling the transition of A. baumannii to a state of heightened resistance and virulence. We show that BfmRS enhances pathogenicity in mammalian hosts, and augments the ability to grow in the presence of diverse antibiotics and tolerate transient, high-level antibiotic exposures. Connected to these effects is the ability of BfmRS to globally reprogram gene expression and control multiple pathways that build, protect, and shape the cell envelope. Moreover, we determined that resistance-enhancing mutations bypassing the need for BfmRS also modulate envelope- and morphology-associated pathways, further linking control of physiology with resistance in A. baumannii. This work uncovers a global control circuit that shifts cellular physiology in ways that promote hospital-associated disease, and points to inhibition of this circuit as a potential strategy for disarming the pathogen.
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Affiliation(s)
- Edward Geisinger
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
- Howard Hughes Medical Institute, Boston, Massachusetts, United States of America
| | - Nadav J. Mortman
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
| | - Germán Vargas-Cuebas
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
| | - Albert K. Tai
- Department of Integrative Physiology and Pathobiology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
| | - Ralph R. Isberg
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
- Howard Hughes Medical Institute, Boston, Massachusetts, United States of America
- * E-mail:
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Dhar S, Kumari H, Balasubramanian D, Mathee K. Cell-wall recycling and synthesis in Escherichia coli and Pseudomonas aeruginosa – their role in the development of resistance. J Med Microbiol 2018; 67:1-21. [DOI: 10.1099/jmm.0.000636] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Affiliation(s)
- Supurna Dhar
- Department of Human and Molecular Genetics, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, USA
| | - Hansi Kumari
- Department of Human and Molecular Genetics, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, USA
| | | | - Kalai Mathee
- Biomolecular Sciences Institute, Florida International University, Miami, FL, USA
- Department of Human and Molecular Genetics, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, USA
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Aminoglycoside Concentrations Required for Synergy with Carbapenems against Pseudomonas aeruginosa Determined via Mechanistic Studies and Modeling. Antimicrob Agents Chemother 2017; 61:AAC.00722-17. [PMID: 28893782 DOI: 10.1128/aac.00722-17] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Accepted: 09/04/2017] [Indexed: 01/24/2023] Open
Abstract
This study aimed to systematically identify the aminoglycoside concentrations required for synergy with a carbapenem and characterize the permeabilizing effect of aminoglycosides on the outer membrane of Pseudomonas aeruginosa Monotherapies and combinations of four aminoglycosides and three carbapenems were studied for activity against P. aeruginosa strain AH298-GFP in 48-h static-concentration time-kill studies (SCTK) (inoculum: 107.6 CFU/ml). The outer membrane-permeabilizing effect of tobramycin alone and in combination with imipenem was characterized via electron microscopy, confocal imaging, and the nitrocefin assay. A mechanism-based model (MBM) was developed to simultaneously describe the time course of bacterial killing and prevention of regrowth by imipenem combined with each of the four aminoglycosides. Notably, 0.25 mg/liter of tobramycin, which was inactive in monotherapy, achieved synergy (i.e., ≥2-log10 more killing than the most active monotherapy at 24 h) combined with imipenem. Electron micrographs, confocal image analyses, and the nitrocefin uptake data showed distinct outer membrane damage by tobramycin, which was more extensive for the combination with imipenem. The MBM indicated that aminoglycosides enhanced the imipenem target site concentration up to 4.27-fold. Tobramycin was the most potent aminoglycoside to permeabilize the outer membrane; tobramycin (0.216 mg/liter), gentamicin (0.739 mg/liter), amikacin (1.70 mg/liter), or streptomycin (5.19 mg/liter) was required for half-maximal permeabilization. In summary, our SCTK, mechanistic studies and MBM indicated that tobramycin was highly synergistic and displayed the maximum outer membrane disruption potential among the tested aminoglycosides. These findings support the optimization of highly promising antibiotic combination dosage regimens for critically ill patients.
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Impacts of Penicillin Binding Protein 2 Inactivation on β-Lactamase Expression and Muropeptide Profile in Stenotrophomonas maltophilia. mSystems 2017; 2:mSystems00077-17. [PMID: 28861525 PMCID: PMC5574705 DOI: 10.1128/msystems.00077-17] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Accepted: 07/28/2017] [Indexed: 12/05/2022] Open
Abstract
Inducible expression of chromosomally encoded β-lactamase(s) is a key mechanism for β-lactam resistance in Enterobacter cloacae, Citrobacter freundii, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia. The muropeptides produced during the peptidoglycan recycling pathway act as activator ligands for β-lactamase(s) induction. The muropeptides 1,6-anhydromuramyl pentapeptide and 1,6-anhydromuramyl tripeptide are the known activator ligands for ampC β-lactamase expression in E. cloacae. Here, we dissected the type of muropepetides for L1/L2 β-lactamase expression in an mrdA deletion mutant of S. maltophilia. Distinct from the findings with the ampC system, 1,6-anhydromuramyl tetrapeptide is the candidate for ΔmrdA-mediated β-lactamase expression in S. maltophilia. Our work extends the understanding of β-lactamase induction and provides valuable information for combating the occurrence of β-lactam resistance. Penicillin binding proteins (PBPs) are involved in peptidoglycan synthesis, and their inactivation is linked to β-lactamase expression in ampR–β-lactamase module–harboring Gram-negative bacteria. There are seven annotated PBP genes, namely, mrcA, mrcB, pbpC, mrdA, ftsI, dacB, and dacC, in the Stenotrophomonas maltophilia genome, and these genes encode PBP1a, PBP1b, PBP1c, PBP2, PBP3, PBP4, and PBP6, respectively. In addition, S. maltophilia harbors two β-lactamase genes, L1 and L2, whose expression is induced via β-lactam challenge. The impact of PBP inactivation on L1/L2 expression was assessed in this study. Inactivation of mrdA resulted in increased L1/L2 expression in the absence of β-lactam challenge, and the underlying mechanism was further elucidated. The roles of ampNG, ampDI (the homologue of Escherichia coli ampD), nagZ, ampR, and creBC in L1/L2 expression mediated by a ΔmrdA mutant strain were assessed via mutant construction and β-lactamase activity determinations. Furthermore, the strain ΔmrdA-mediated change in the muropeptide profile was assessed using liquid chromatography mass spectrometry (LC-MS). The mutant ΔmrdA-mediated L1/L2 expression relied on functional AmpNG, AmpR, and NagZ, was restricted by AmpDI, and was less related to the CreBC two-component system. Inactivation of mrdA significantly increased the levels of total and periplasmic N-acetylglucosaminyl-1,6-anhydro-N-acetylmuramyl-l-alanyl-d-glutamyl-meso-diamnopimelic acid-d-alanine (GlcNAc-anhMurNAc tetrapeptide, or M4N), supporting that the critical activator ligands for mutant strain ΔmrdA-mediated L1/L2 expression are anhMurNAc tetrapeptides. IMPORTANCE Inducible expression of chromosomally encoded β-lactamase(s) is a key mechanism for β-lactam resistance in Enterobacter cloacae, Citrobacter freundii, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia. The muropeptides produced during the peptidoglycan recycling pathway act as activator ligands for β-lactamase(s) induction. The muropeptides 1,6-anhydromuramyl pentapeptide and 1,6-anhydromuramyl tripeptide are the known activator ligands for ampC β-lactamase expression in E. cloacae. Here, we dissected the type of muropepetides for L1/L2 β-lactamase expression in an mrdA deletion mutant of S. maltophilia. Distinct from the findings with the ampC system, 1,6-anhydromuramyl tetrapeptide is the candidate for ΔmrdA-mediated β-lactamase expression in S. maltophilia. Our work extends the understanding of β-lactamase induction and provides valuable information for combating the occurrence of β-lactam resistance.
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Penicillin-Binding Protein 3 Is Essential for Growth of Pseudomonas aeruginosa. Antimicrob Agents Chemother 2016; 61:AAC.01651-16. [PMID: 27821444 DOI: 10.1128/aac.01651-16] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Accepted: 10/23/2016] [Indexed: 12/19/2022] Open
Abstract
Penicillin-binding proteins (PBPs) function as transpeptidases, carboxypeptidases, or endopeptidases during peptidoglycan synthesis in bacteria. As the well-known drug targets for β-lactam antibiotics, the physiological functions of PBPs and whether they are essential for growth are of significant interest. The pathogen Pseudomonas aeruginosa poses a particular risk to immunocompromised and cystic fibrosis patients, and infections caused by this pathogen are difficult to treat due to antibiotic resistance. To identify potential drug targets among the PBPs in P. aeruginosa, we performed gene knockouts of all the high-molecular-mass (HMM) PBPs and determined the impacts on cell growth and morphology, susceptibility to β-lactams, peptidoglycan structure, virulence, and pathogenicity. Disruptions of the transpeptidase domains of most HMM PBPs, including double disruptions, had only minimal effects on cell growth. The exception was PBP3, where cell growth occurred only when the protein was conditionally expressed on an integrated plasmid. Conditional deletion of PBP3 also caused a defect in cell division and increased susceptibility to β-lactams. Knockout of PBP1a led to impaired motility, and this observation, together with its localization at the cell poles, suggests its involvement in flagellar function. Overall, these findings reveal that PBP3 represents the most promising target for drug discovery against P. aeruginosa, whereas other HMM PBPs have less potential.
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Aguilera Rossi CG, Gómez-Puertas P, Ayala Serrano JA. In vivo functional and molecular characterization of the Penicillin-Binding Protein 4 (DacB) of Pseudomonas aeruginosa. BMC Microbiol 2016; 16:234. [PMID: 27716106 PMCID: PMC5054556 DOI: 10.1186/s12866-016-0853-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Accepted: 09/27/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Community and nosocomial infections by Pseudomonas aeruginosa still create a major therapeutic challenge. The resistance of this opportunist pathogen to β-lactam antibiotics is determined mainly by production of the inactivating enzyme AmpC, a class C cephalosporinase with a regulation system more complex than those found in members of the Enterobacteriaceae family. This regulatory system also participates directly in peptidoglycan turnover and recycling. One of the regulatory mechanisms for AmpC expression, recently identified in clinical isolates, is the inactivation of LMM-PBP4 (Low-Molecular-Mass Penicillin-Binding Protein 4), a protein whose catalytic activity on natural substrates has remained uncharacterized until now. RESULTS We carried out in vivo activity trials for LMM-PBP4 of Pseudomonas aeruginosa on macromolecular peptidoglycan of Escherichia coli and Pseudomonas aeruginosa. The results showed a decrease in the relative quantity of dimeric, trimeric and anhydrous units, and a smaller reduction in monomer disaccharide pentapeptide (M5) levels, validating the occurrence of D,D-carboxypeptidase and D,D-endopeptidase activities. Under conditions of induction for this protein and cefoxitin treatment, the reduction in M5 is not fully efficient, implying that LMM-PBP4 of Pseudomonas aeruginosa presents better behaviour as a D,D-endopeptidase. Kinetic evaluation of the direct D,D-peptidase activity of this protein on natural muropeptides M5 and D45 confirmed this bifunctionality and the greater affinity of LMM-PBP4 for its dimeric substrate. A three-dimensional model for the monomeric unit of LMM-PBP4 provided structural information which supports its catalytic performance. CONCLUSIONS LMM-PBP4 of Pseudomonas aeruginosa is a bifunctional enzyme presenting both D,D-carboxypeptidase and D,D-endopeptidase activities; the D,D-endopeptidase function is predominant. Our study provides unprecedented functional and structural information which supports the proposal of this protein as a potential hydrolase-autolysin associated with peptidoglycan maturation and recycling. The fact that mutant PBP4 induces AmpC, may indicate that a putative muropeptide-subunit product of the DD-EPase activity of PBP4 could be a negative regulator of the pathway. This data contributes to understanding of the regulatory aspects of resistance to β-lactam antibiotics in this bacterial model.
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Affiliation(s)
- Cristian Gustavo Aguilera Rossi
- Departamento de Ciencias Preclínicas, Facultad de Medicina, Universidad de La Frontera, Temuco, Chile.,Laboratorio de División Celular Bacteriana y Resistencia a Antibióticos, Centro de Biología Molecular "Severo Ochoa", Universidad Autónoma de Madrid-CSIC, Madrid, Spain
| | - Paulino Gómez-Puertas
- Grupo de Modelado Molecular, Centro de Biología Molecular "Severo Ochoa", Universidad Autónoma de Madrid-CSIC, Madrid, Spain
| | - Juan Alfonso Ayala Serrano
- Laboratorio de División Celular Bacteriana y Resistencia a Antibióticos, Centro de Biología Molecular "Severo Ochoa", Universidad Autónoma de Madrid-CSIC, Madrid, Spain.
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Chirani AS, Majidzadeh R, Dabiri H, Rezaei J, Esmaili A, Kord YA, Tehrani NK, Attaran N. Immunological study on integrated PilQ and disulphide loop region of PilA against acute Pseudomonas aeruginosa infection: In silico analysis and in vitro production. JOURNAL OF ACUTE DISEASE 2016. [DOI: 10.1016/j.joad.2015.11.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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13
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Desmarais SM, Tropini C, Miguel A, Cava F, Monds RD, de Pedro MA, Huang KC. High-throughput, Highly Sensitive Analyses of Bacterial Morphogenesis Using Ultra Performance Liquid Chromatography. J Biol Chem 2015; 290:31090-100. [PMID: 26468288 DOI: 10.1074/jbc.m115.661660] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Indexed: 01/22/2023] Open
Abstract
The bacterial cell wall is a network of glycan strands cross-linked by short peptides (peptidoglycan); it is responsible for the mechanical integrity of the cell and shape determination. Liquid chromatography can be used to measure the abundance of the muropeptide subunits composing the cell wall. Characteristics such as the degree of cross-linking and average glycan strand length are known to vary across species. However, a systematic comparison among strains of a given species has yet to be undertaken, making it difficult to assess the origins of variability in peptidoglycan composition. We present a protocol for muropeptide analysis using ultra performance liquid chromatography (UPLC) and demonstrate that UPLC achieves resolution comparable with that of HPLC while requiring orders of magnitude less injection volume and a fraction of the elution time. We also developed a software platform to automate the identification and quantification of chromatographic peaks, which we demonstrate has improved accuracy relative to other software. This combined experimental and computational methodology revealed that peptidoglycan composition was approximately maintained across strains from three Gram-negative species despite taxonomical and morphological differences. Peptidoglycan composition and density were maintained after we systematically altered cell size in Escherichia coli using the antibiotic A22, indicating that cell shape is largely decoupled from the biochemistry of peptidoglycan synthesis. High-throughput, sensitive UPLC combined with our automated software for chromatographic analysis will accelerate the discovery of peptidoglycan composition and the molecular mechanisms of cell wall structure determination.
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Affiliation(s)
| | - Carolina Tropini
- From the Departments of Bioengineering and the Biophysics Program, Stanford University, Stanford, California 94305
| | | | - Felipe Cava
- the Department of Molecular Biology and Laboratory for Molecular Infection Medicine Sweden, Umeå Centre for Microbial Research, Umeå University, Umeå, 90187 Sweden
| | - Russell D Monds
- From the Departments of Bioengineering and the Bio-X Program, Stanford University, Stanford, California 94305, and
| | - Miguel A de Pedro
- the Universidad Autonoma de Madrid, Campus de Cantoblanco, 28049 Madrid, Spain
| | - Kerwyn Casey Huang
- From the Departments of Bioengineering and the Biophysics Program, Stanford University, Stanford, California 94305, the Bio-X Program, Stanford University, Stanford, California 94305, and Microbiology and Immunology, Stanford University School of Medicine, Stanford, California 94305,
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14
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Livermore DM, Mushtaq S, Warner M, Woodford N. Activity of OP0595/β-lactam combinations against Gram-negative bacteria with extended-spectrum, AmpC and carbapenem-hydrolysing β-lactamases. J Antimicrob Chemother 2015; 70:3032-41. [DOI: 10.1093/jac/dkv239] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Accepted: 07/10/2015] [Indexed: 11/14/2022] Open
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15
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An YD, Du QZ, Tong LY, Yu ZW, Gong XW. Cloning, expression and purification of penicillin-binding protein 3 from Pseudomonas aeruginosa CMCC 10104. Protein Expr Purif 2014; 110:37-42. [PMID: 25514204 DOI: 10.1016/j.pep.2014.12.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2014] [Revised: 12/05/2014] [Accepted: 12/07/2014] [Indexed: 11/18/2022]
Abstract
Penicillin-binding protein 3 (PBP3) of Pseudomonas aeruginosa is the primary target of β-lactams used to treat pseudomonas infections. Meanwhile, structure change and overproduction of PBP3 play important roles in the drug resistance of P. aeruginosa. Therefore, studies on the gene and structure of PBP3 are urgently needed. P. aeruginosa CMCC 10104 is a type culture strain common used in China. However, there is no report on its genomic and proteomic profiles. In this study, based on ftsI of P. aeruginosa PAO1, the gene encoding PBP3 was cloned from CMCC 10104. A truncated version of the ftsI gene, omitting the bases encoding the hydrophobic leader peptide (amino acids 1-34), was amplified by PCR. The cloned DNA shared 99.76% identity with ftsI from PAO1. Only four bases were different (66 C-A, 1020 T-C, 1233 T-C, and 1527 T-C). However, there were no differences between their deduced amino acid sequences. The recombinant PBP3 (rPBP3), containing a 6-histidine tag, was expressed in Escherichia coli BL21 (DE3). Immobilized metal affinity chromatography (IMAC) with Ni(2+)-NTA agarose was used for its purification. The purified rPBP3 was identified by SDS-PAGE and western blot analysis, and showed a single band at about 60kDa with purity higher than 95%. The penicillin-binding assay indicated that the obtained rPBP3 was functional and not hindered by the presence of the C-terminal His-tag. The protocol described in this study offers a method for obtaining purified recombinant PBP3 from P. aeruginosa CMCC 10104.
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Affiliation(s)
- Yan Dong An
- College of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou 310018, China
| | - Qi Zhen Du
- Zhejiang A&F University, Hangzhou 311300, China
| | - Li Yan Tong
- College of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou 310018, China
| | - Zhao Wu Yu
- College of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou 310018, China
| | - Xing Wen Gong
- College of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou 310018, China.
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16
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Fluorescence anisotropy-based measurement of Pseudomonas aeruginosa penicillin-binding protein 2 transpeptidase inhibitor acylation rate constants. Anal Biochem 2014; 463:15-22. [DOI: 10.1016/j.ab.2014.06.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2014] [Revised: 06/03/2014] [Accepted: 06/05/2014] [Indexed: 11/20/2022]
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17
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Zavascki AP, Carvalhaes CG, Picão RC, Gales AC. Multidrug-resistantPseudomonas aeruginosaandAcinetobacter baumannii: resistance mechanisms and implications for therapy. Expert Rev Anti Infect Ther 2014; 8:71-93. [DOI: 10.1586/eri.09.108] [Citation(s) in RCA: 203] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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18
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Desmarais SM, De Pedro MA, Cava F, Huang KC. Peptidoglycan at its peaks: how chromatographic analyses can reveal bacterial cell wall structure and assembly. Mol Microbiol 2013; 89:1-13. [PMID: 23679048 DOI: 10.1111/mmi.12266] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/15/2013] [Indexed: 02/02/2023]
Abstract
The peptidoglycan (PG) cell wall is a unique macromolecule responsible for both shape determination and cellular integrity under osmotic stress in virtually all bacteria. A quantitative understanding of the relationships between PG architecture, morphogenesis, immune system activation and pathogenesis can provide molecular-scale insights into the function of proteins involved in cell wall synthesis and cell growth. High-performance liquid chromatography (HPLC) has played an important role in our understanding of the structural and chemical complexity of the cell wall by providing an analytical method to quantify differences in chemical composition. Here, we present a primer on the basic chemical features of wall structure that can be revealed through HPLC, along with a description of the applications of HPLC PG analyses for interpreting the effects of genetic and chemical perturbations to a variety of bacterial species in different environments. We describe the physical consequences of different PG compositions on cell shape, and review complementary experimental and computational methodologies for PG analysis. Finally, we present a partial list of future targets of development for HPLC and related techniques.
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19
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Changes to its peptidoglycan-remodeling enzyme repertoire modulate β-lactam resistance in Pseudomonas aeruginosa. Antimicrob Agents Chemother 2013; 57:3078-84. [PMID: 23612194 DOI: 10.1128/aac.00268-13] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas aeruginosa is a leading cause of hospital-acquired infections and is resistant to many antibiotics. Among its primary mechanisms of resistance is expression of a chromosomally encoded AmpC β-lactamase that inactivates β-lactams. The mechanisms leading to AmpC expression in P. aeruginosa remain incompletely understood but are intricately linked to cell wall metabolism. To better understand the roles of peptidoglycan-active enzymes in AmpC expression-and consequent β-lactam resistance-a phenotypic screen of P. aeruginosa mutants lacking such enzymes was performed. Mutants lacking one of four lytic transglycosylases (LTs) or the nonessential penicillin-binding protein PBP4 (dacB) had altered β-lactam resistance. mltF and slt mutants with reduced β-lactam resistance were designated WIMPs (wall-impaired mutant phenotypes), while highly resistant dacB, sltB1, and mltB mutants were designated HARMs (high-level AmpC resistant mutants). Double mutants lacking dacB and sltB1 had extreme piperacillin resistance (>256 μg/ml) compared to either of the single knockouts (64 μg/ml for a dacB mutant and 12 μg/ml for an sltB1 mutant). Inactivation of ampC reverted these mutants to wild-type susceptibility, confirming that AmpC expression underlies resistance. dacB mutants had constitutively elevated AmpC expression, but the LT mutants had wild-type levels of AmpC in the absence of antibiotic exposure. These data suggest that there are at least two different pathways leading to AmpC expression in P. aeruginosa and that their simultaneous activation leads to extreme β-lactam resistance.
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20
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Nikolaidis I, Izoré T, Job V, Thielens N, Breukink E, Dessen A. Calcium-dependent complex formation between PBP2 and lytic transglycosylase SltB1 of Pseudomonas aeruginosa. Microb Drug Resist 2012; 18:298-305. [PMID: 22432706 DOI: 10.1089/mdr.2012.0006] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In Gram-negative bacteria, the bacterial cell wall biosynthetic mechanism requires the coordinated action of enzymes and structural proteins located in the cytoplasm, within the membrane, and in the periplasm of the cell. Its main component, peptidoglycan (PG), is essential for cell division and wall elongation. Penicillin-binding proteins (PBPs) catalyze the last steps of PG biosynthesis, namely the polymerization of glycan chains and the cross-linking of stem peptides, and can be either monofunctional or bifunctional. Their action is coordinated with that of other enzymes essential for cell-wall biosynthesis, such as lytic transglycosylases (LT). Here, we have studied SltB1, an LT from Pseudomonas aeruginosa, and identified that it forms a complex with PBP2, a monofunctional enzyme, which requires the presence of Ca(2+). In addition, we have solved the structure of SltB1 to a high resolution, and identified that it harbors an EF-hand like motif containing a Ca(2+) ion displaying bipyramidal coordination. These studies provide initial structural details that shed light on the interactions between the PG biosynthesis enzymes in P. aeruginosa.
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Affiliation(s)
- Ioulia Nikolaidis
- Bacterial Pathogenesis Group, Institut de Biologie Structurale (IBS), Université Grenoble I, Grenoble, France
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21
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Deletion and overexpression studies on DacB2, a putative low molecular mass penicillin binding protein from Mycobacterium tuberculosis H(37)Rv. Microb Pathog 2011; 52:109-16. [PMID: 22138550 DOI: 10.1016/j.micpath.2011.11.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2011] [Revised: 11/14/2011] [Accepted: 11/21/2011] [Indexed: 11/20/2022]
Abstract
Mycobacterium tuberculosis genome encodes several high and low molecular mass penicillin binding proteins. One such low molecular mass protein is DacB2 encoded by open reading frame Rv2911 of M. tuberculosis which is predicted to play a role in peptidoglycan synthesis. In this study we have tried to gain an insight into the role of this accessory cell division protein in mycobacterial physiology by performing overexpression and deletion studies. The overproduction of DacB2 in non-pathogenic, fast growing mycobacterium Mycobacterium smegmatis mc(2)155 resulted in reduced growth, an altered colony morphology, a defect in sliding motility and biofilm formation. A point mutant of DacB2 was made wherein the active site serine residue was mutated to cysteine to abolish the penicillin binding function of protein. The overexpression of mutant protein showed similar results indicating that the effects produced were independent of protein's penicillin binding function. The gene encoding DacB2 was deleted in M. tuberculosis by specialized transduction method. The deletion mutant showed reduced growth in Sauton's medium under acidic and low oxygen availability. The in vitro infection studies with THP-1 cells showed increased intracellular survival of dacB2 mutant compared to parent and complemented strains. The colony morphology and antibiotic sensitivity of mutant and wild-type strains were similar.
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22
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Production and purification of the penicillin-binding protein 3 from Pseudomonas aeruginosa. Protein Expr Purif 2010; 73:177-83. [DOI: 10.1016/j.pep.2010.05.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2010] [Revised: 04/30/2010] [Accepted: 05/10/2010] [Indexed: 11/17/2022]
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23
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Specht KM, Sheetz KH, Alexander CM, Lamech LT, O’Connor LH, Walker DM, Stevenson HP. Expression and Characterization of Penicillin-Binding Proteins in Burkholderia cenocepacia. Curr Microbiol 2009; 60:274-9. [DOI: 10.1007/s00284-009-9537-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2009] [Accepted: 10/26/2009] [Indexed: 11/29/2022]
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24
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Interaction of penicillin-binding protein 2 with soluble lytic transglycosylase B1 in Pseudomonas aeruginosa. J Bacteriol 2008; 190:6922-6. [PMID: 18708507 DOI: 10.1128/jb.00934-08] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Soluble lytic transglycosylase B1 from Pseudomonas aeruginosa was coupled to Sepharose and used to immobilize interaction partners from membrane protein extracts. Penicillin-binding protein 2 (PBP2) was identified as a binding partner, suggesting that the two proteins function together in the biosynthesis of peptidoglycan. By use of an engineered truncated derivative, the N-terminal module of PBP2 was found to confer the binding properties.
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25
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Giske CG, Buarø L, Sundsfjord A, Wretlind B. Alterations of porin, pumps, and penicillin-binding proteins in carbapenem resistant clinical isolates of Pseudomonas aeruginosa. Microb Drug Resist 2008; 14:23-30. [PMID: 18321207 DOI: 10.1089/mdr.2008.0778] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Carbapenem-resistant clinical isolates of Pseudomonas aeruginosa from Sweden and Norway (n=27) were characterized regarding transcription of genes encoding OprD, efflux pumps MexAB-OprM and MexCD-OprJ, as well as penicillin-binding proteins (PBP) 2 and 3. Quantification of mRNA was performed with real-time RT-PCR. Levels of mRNA in clinical isolates were compared to ATCC 27853 and average transcription levels of four carbapenem-susceptible clinical isolates of P. aeruginosa. Sequencing of oprD, pbp 2, and pbp 3 was performed in selected isolates. An efflux inhibition assay was performed with Phe-Arg-beta-naphtylamide. Most carbapenem-resistant isolates had decreased levels of oprD mRNA. Among six isolates with normal amount of oprD mRNA, half of them had significant OprD sequence alterations. Increased transcription of mexB was observed in 16 of 23 meropenem-resistant isolates, and one isolate showed mexD hyperproduction. Decreased amount of pbp 2 and pbp 3 was found in two and three isolates, respectively. Sequencing of pbp 2 and 3 revealed no amino acid changes potentially leading to conformational changes. In conclusion, OprD changes were the predominant mechanism of high-level carbapenem resistance, and increased transcription of mexB was often present in meropenem-resistant isolates. Reduced transcription of pbp 2 and 3 may contribute to the carbapenem resistance.
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Affiliation(s)
- Christian G Giske
- Department of Clinical Microbiology, Karolinska Institutet-MTC, Karolinska University Hospital Solna, Stockholm, Sweden.
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26
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Farra A, Islam S, Strålfors A, Sörberg M, Wretlind B. Role of outer membrane protein OprD and penicillin-binding proteins in resistance of Pseudomonas aeruginosa to imipenem and meropenem. Int J Antimicrob Agents 2008; 31:427-33. [PMID: 18375104 DOI: 10.1016/j.ijantimicag.2007.12.016] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2007] [Revised: 12/13/2007] [Accepted: 12/13/2007] [Indexed: 10/22/2022]
Abstract
The main mechanism of imipenem resistance in Pseudomonas aeruginosa is via downregulation of the gene for OprD porin. In a previous study, it was shown that the level of resistance did not parallel with the degree of downregulation of the porin gene, thus arguing for the existence of other resistance mechanisms. Penicillin-binding protein (PBP) 2 and PBP3 are involved in carbapenem resistance in Escherichia coli. The genes for PBPs were sequenced in three imipenem-resistant clinical strains and these strains were conjugated with two susceptible P. aeruginosa PA0 strains, selecting for auxotrophic markers. In all the clinical and resistant isolates there was no obvious elevation of AmpC cephalosporinase. The active sites of PBP1b (ponB), PBP2 (pbpA), PBP3 (pbpB) and PBP6 (dacC) had no mutations in any of the examined strains. Production of oprD mRNA was significantly lower in clinical strains and transconjugants after selection for the proB marker (PA4565 at 5113kb). The clinical strains had alterations in OprD that were not found in transconjugants. Our findings suggest that PBPs do not play a role in imipenem resistance in the clinical strains examined here, but that a regulatory gene for oprD contributing to carbapenem resistance is located close to the proB gene.
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Affiliation(s)
- Anna Farra
- Division of Internal Medicine, Department of Infectious Diseases, Karolinska Institutet, Karolinska University Hospital, Solna, Stockholm, Sweden
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27
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Scheurwater EM, Pfeffer JM, Clarke AJ. Production and purification of the bacterial autolysin N-acetylmuramoyl-l-alanine amidase B from Pseudomonas aeruginosa. Protein Expr Purif 2007; 56:128-37. [PMID: 17723308 DOI: 10.1016/j.pep.2007.06.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2007] [Revised: 06/15/2007] [Accepted: 06/26/2007] [Indexed: 11/20/2022]
Abstract
The bacterial cell wall heteropolymer peptidoglycan is not a static structure as it is constantly being made and recycled throughout the bacterium's life cycle. This turnover of peptidoglycan is a highly coordinated event involving a complement of autolytic enzymes that include those with specificity for either the carbohydrate or the peptide linkages of peptidoglycan. One major class of these autolysins are the N-acetylmuramoyl-L-alanine amidases which cleave the amide linkage between the stem peptides and the lactyl moiety of muramoyl residues. They are required in the periplasm for cell separation during division and in both the periplasm and cytoplasm to trim soluble released PG fragments during turnover for recycling. The gene encoding N-acetylmuramoyl-L-alanine amidase B in Pseudomonas aeruginosa was cloned and over-expressed in Escherichia coli. The recombinant protein with a C-terminal His-tag was purified to apparent homogeneity by a combination of affinity and cation-exchange chromatographies using Ni(2+)NTA-agarose and Source S, respectively. Four separate assays involving zymography, light scattering, HPLC and MALDI-TOF mass spectrometry were used to confirm the activity of the protein as an N-acetylmuramoyl-L-alanine amidase.
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Affiliation(s)
- Edie M Scheurwater
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
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28
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Legaree BA, Adams CB, Clarke AJ. Overproduction of penicillin-binding protein 2 and its inactive variants causes morphological changes and lysis in Escherichia coli. J Bacteriol 2007; 189:4975-83. [PMID: 17513478 PMCID: PMC1951868 DOI: 10.1128/jb.00207-07] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Penicillin-binding protein 2 (PBP 2) has long been known to be essential for rod-shaped morphology in gram-negative bacteria, including Escherichia coli and Pseudomonas aeruginosa. In the course of earlier studies with P. aeruginosa PBP 2, we observed that E. coli was sensitive to the overexpression of its gene, pbpA. In this study, we examined E. coli overproducing both P. aeruginosa and E. coli PBP 2. Growth of cells entered a stationary phase soon after induction of gene expression, and cells began to lyse upon prolonged incubation. Concomitant with the growth retardation, cells were observed to have changed morphologically from typical rods into enlarged spheres. Inactive derivatives of the PBP 2s were engineered, involving site-specific replacement of their catalytic Ser residues with Ala in their transpeptidase module. Overproduction of these inactive PBPs resulted in identical effects. Likewise, overproduction of PBP 2 derivatives possessing only their N-terminal non-penicillin-binding module (i.e., lacking their C-terminal transpeptidase module) produced similar effects. However, E. coli overproducing engineered derivatives of PBP 2 lacking their noncleavable, N-terminal signal sequence and membrane anchor were found to grow and divide at the same rate as control cells. The morphological effects and lysis were also eliminated entirely when overproduction of PBP 2 and variants was conducted with E. coli MHD79, a strain lacking six lytic transglycosylases. A possible interaction between the N-terminal domain of PBP 2 and lytic transglycosylases in vivo through the formation of multienzyme complexes is discussed.
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Affiliation(s)
- Blaine A Legaree
- Guelph-Waterloo Centre for Graduate Work in Chemistry and Biochemistry, Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
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