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Bon CG, Grigg JC, Lee J, Robb CS, Caveney NA, Eltis LD, Strynadka NCJ. Structural and kinetic analysis of the monofunctional Staphylococcus aureus PBP1. J Struct Biol 2024; 216:108086. [PMID: 38527711 DOI: 10.1016/j.jsb.2024.108086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2024] [Revised: 03/13/2024] [Accepted: 03/14/2024] [Indexed: 03/27/2024]
Abstract
Staphylococcus aureus, an ESKAPE pathogen, is a major clinical concern due to its pathogenicity and manifold antimicrobial resistance mechanisms. The commonly used β-lactam antibiotics target bacterial penicillin-binding proteins (PBPs) and inhibit crosslinking of peptidoglycan strands that comprise the bacterial cell wall mesh, initiating a cascade of effects leading to bacterial cell death. S. aureus PBP1 is involved in synthesis of the bacterial cell wall during division and its presence is essential for survival of both antibiotic susceptible and resistant S. aureus strains. Here, we present X-ray crystallographic data for S. aureus PBP1 in its apo form as well as acyl-enzyme structures with distinct classes of β-lactam antibiotics representing the penicillins, carbapenems, and cephalosporins, respectively: oxacillin, ertapenem and cephalexin. Our structural data suggest that the PBP1 active site is readily accessible for substrate, with little conformational change in key structural elements required for its covalent acylation of β-lactam inhibitors. Stopped-flow kinetic analysis and gel-based competition assays support the structural observations, with even the weakest performing β-lactams still having comparatively high acylation rates and affinities for PBP1. Our structural and kinetic analysis sheds insight into the ligand-PBP interactions that drive antibiotic efficacy against these historically useful antimicrobial targets and expands on current knowledge for future drug design and treatment of S. aureus infections.
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Affiliation(s)
- Christopher G Bon
- Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada; Centre for Blood Research, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Jason C Grigg
- Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada; Department of Microbiology and Immunology, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Jaeyong Lee
- Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada; Centre for Blood Research, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Craig S Robb
- Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada; Centre for Blood Research, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Nathanael A Caveney
- Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada; Centre for Blood Research, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Lindsay D Eltis
- Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada; Department of Microbiology and Immunology, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Natalie C J Strynadka
- Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada; Centre for Blood Research, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
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2
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Micelli C, Dai Y, Raustad N, Isberg RR, Dowson CG, Lloyd AJ, Geisinger E, Crow A, Roper DI. A conserved zinc-binding site in Acinetobacter baumannii PBP2 required for elongasome-directed bacterial cell shape. Proc Natl Acad Sci U S A 2023; 120:e2215237120. [PMID: 36787358 PMCID: PMC9974482 DOI: 10.1073/pnas.2215237120] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Accepted: 01/09/2023] [Indexed: 02/15/2023] Open
Abstract
Acinetobacter baumannii is a gram-negative bacterial pathogen that causes challenging nosocomial infections. β-lactam targeting of penicillin-binding protein (PBP)-mediated cell wall peptidoglycan (PG) formation is a well-established antimicrobial strategy. Exposure to carbapenems or zinc (Zn)-deprived growth conditions leads to a rod-to-sphere morphological transition in A. baumannii, an effect resembling that caused by deficiency in the RodA-PBP2 PG synthesis complex required for cell wall elongation. While it is recognized that carbapenems preferentially acylate PBP2 in A. baumannii and therefore block the transpeptidase function of the RodA-PBP2 system, the molecular details underpinning cell wall elongation inhibition upon Zn starvation remain undefined. Here, we report the X-ray crystal structure of A. baumannii PBP2, revealing an unexpected Zn coordination site in the transpeptidase domain required for protein stability. Mutations in the Zn-binding site of PBP2 cause a loss of bacterial rod shape and increase susceptibility to β-lactams, therefore providing a direct rationale for cell wall shape maintenance and Zn homeostasis in A. baumannii. Furthermore, the Zn-coordinating residues are conserved in various β- and γ-proteobacterial PBP2 orthologs, consistent with a widespread Zn-binding requirement for function that has been previously unknown. Due to the emergence of resistance to virtually all marketed antibiotic classes, alternative or complementary antimicrobial strategies need to be explored. These findings offer a perspective for dual inhibition of Zn-dependent PG synthases and metallo-β-lactamases by metal chelating agents, considered the most sought-after adjuvants to restore β-lactam potency against gram-negative bacteria.
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Affiliation(s)
- Carmina Micelli
- School of Life Sciences, University of Warwick, CoventryCV4 7AL, United Kingdom
| | - Yunfei Dai
- Department of Biology, Northeastern University, Boston, MA02115
| | - Nicole Raustad
- Department of Biology, Northeastern University, Boston, MA02115
| | - Ralph R. Isberg
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA02111
| | | | - Adrian J. Lloyd
- School of Life Sciences, University of Warwick, CoventryCV4 7AL, United Kingdom
| | | | - Allister Crow
- School of Life Sciences, University of Warwick, CoventryCV4 7AL, United Kingdom
| | - David I. Roper
- School of Life Sciences, University of Warwick, CoventryCV4 7AL, United Kingdom
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3
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McLaughlin HP, Gulvik CA, Sue D. In silico analyses of penicillin binding proteins in Burkholderia pseudomallei uncovers SNPs with utility for phylogeography, species differentiation, and sequence typing. PLoS Negl Trop Dis 2022; 16:e0009882. [PMID: 35417451 PMCID: PMC9037935 DOI: 10.1371/journal.pntd.0009882] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Revised: 04/25/2022] [Accepted: 03/15/2022] [Indexed: 11/26/2022] Open
Abstract
Burkholderia pseudomallei causes melioidosis. Sequence typing this pathogen can reveal geographical origin and uncover epidemiological associations. Here, we describe B. pseudomallei genes encoding putative penicillin binding proteins (PBPs) and investigate their utility for determining phylogeography and differentiating closely related species. We performed in silico analysis to characterize 10 PBP homologs in B. pseudomallei 1026b. As PBP active site mutations can confer β-lactam resistance in Gram-negative bacteria, PBP sequences in two resistant B. pseudomallei strains were examined for similar alterations. Sequence alignments revealed single amino acid polymorphisms (SAAPs) unique to the multidrug resistant strain Bp1651 in the transpeptidase domains of two PBPs, but not directly within the active sites. Using BLASTn analyses of complete assembled genomes in the NCBI database, we determined genes encoding PBPs were conserved among B. pseudomallei (n = 101) and Burkholderia mallei (n = 26) strains. Within these genes, single nucleotide polymorphisms (SNPs) useful for predicting geographic origin of B. pseudomallei were uncovered. SNPs unique to B. mallei were also identified. Based on 11 SNPs identified in two genes encoding predicted PBP-3s, a dual-locus sequence typing (DLST) scheme was developed. The robustness of this typing scheme was assessed using 1,523 RefSeq genomes from B. pseudomallei (n = 1,442) and B. mallei (n = 81) strains, resulting in 32 sequence types (STs). Compared to multi-locus sequence typing (MLST), the DLST scheme demonstrated less resolution to support the continental separation of Australian B. pseudomallei strains. However, several STs were unique to strains originating from a specific country or region. The phylogeography of Western Hemisphere B. pseudomallei strains was more highly resolved by DLST compared to internal transcribed spacer (ITS) typing, and all B. mallei strains formed a single ST. Conserved genes encoding PBPs in B. pseudomallei are useful for strain typing, can enhance predictions of geographic origin, and differentiate strains of closely related Burkholderia species. Burkholderia pseudomallei causes the life-threatening disease melioidosis and is considered a biological threat and select agent by the United States government. This soil-dwelling bacterium is commonly found in regions of southeast Asia and northern Australia, but it is also detected in other tropical and sub-tropical areas around the world. With a predicted global burden of 165,000 annual cases and mortality rate that can exceed 40% without prompt and appropriate antibiotic treatment, understanding the epidemiology of melioidosis and mechanisms of antibiotic resistance in B. pseudomallei can benefit public health and safety. Recently, we identified ten conserved genes encoding putative penicillin binding proteins (PBPs) in B. pseudomallei. Here, we examined B. pseudomallei PBP sequences for amino acid mutations that may contribute to β-lactam resistance. We also uncovered nucleotide mutations with utility to predict the geographical origin of B. pseudomallei strains and to differentiate closely related Burkholderia species. Based on 11 informative single nucleotide polymorphisms in two genes each encoding a PBP-3, we developed a simple, targeted dual-locus typing approach.
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Affiliation(s)
- Heather P. McLaughlin
- Biodefense Research and Development Laboratory, Division of Preparedness and Emerging Infections, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
- * E-mail:
| | - Christopher A. Gulvik
- Zoonoses and Select Agent Laboratory, Division of High-Consequence Pathogens and Pathology, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
| | - David Sue
- Biodefense Research and Development Laboratory, Division of Preparedness and Emerging Infections, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
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4
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β-lactam Resistance in Pseudomonas aeruginosa: Current Status, Future Prospects. Pathogens 2021; 10:pathogens10121638. [PMID: 34959593 PMCID: PMC8706265 DOI: 10.3390/pathogens10121638] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Revised: 12/06/2021] [Accepted: 12/16/2021] [Indexed: 12/12/2022] Open
Abstract
Pseudomonas aeruginosa is a major opportunistic pathogen, causing a wide range of acute and chronic infections. β-lactam antibiotics including penicillins, carbapenems, monobactams, and cephalosporins play a key role in the treatment of P. aeruginosa infections. However, a significant number of isolates of these bacteria are resistant to β-lactams, complicating treatment of infections and leading to worse outcomes for patients. In this review, we summarize studies demonstrating the health and economic impacts associated with β-lactam-resistant P. aeruginosa. We then describe how β-lactams bind to and inhibit P. aeruginosa penicillin-binding proteins that are required for synthesis and remodelling of peptidoglycan. Resistance to β-lactams is multifactorial and can involve changes to a key target protein, penicillin-binding protein 3, that is essential for cell division; reduced uptake or increased efflux of β-lactams; degradation of β-lactam antibiotics by increased expression or altered substrate specificity of an AmpC β-lactamase, or by the acquisition of β-lactamases through horizontal gene transfer; and changes to biofilm formation and metabolism. The current understanding of these mechanisms is discussed. Lastly, important knowledge gaps are identified, and possible strategies for enhancing the effectiveness of β-lactam antibiotics in treating P. aeruginosa infections are considered.
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6
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Novel and Improved Crystal Structures of H. influenzae, E. coli and P. aeruginosa Penicillin-Binding Protein 3 (PBP3) and N. gonorrhoeae PBP2: Toward a Better Understanding of β-Lactam Target-Mediated Resistance. J Mol Biol 2019; 431:3501-3519. [PMID: 31301409 DOI: 10.1016/j.jmb.2019.07.010] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Revised: 07/02/2019] [Accepted: 07/02/2019] [Indexed: 01/26/2023]
Abstract
Even with the emergence of antibiotic resistance, penicillin and the wider family of β-lactams have remained the single most important family of antibiotics. The periplasmic/extra-cytoplasmic targets of penicillin are a family of enzymes with a highly conserved catalytic activity involved in the final stage of bacterial cell wall (peptidoglycan) biosynthesis. Named after their ability to bind penicillin, rather than their catalytic activity, these key targets are called penicillin-binding proteins (PBPs). Resistance is predominantly mediated by reducing the target drug concentration via β-lactamases; however, naturally transformable bacteria have also acquired target-mediated resistance by inter-species recombination. Here we focus on structural based interpretations of amino acid alterations associated with the emergence of resistance within clinical isolates and include new PBP3 structures along with new, and improved, PBP-β-lactam co-structures.
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7
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Alexander JAN, Chatterjee SS, Hamilton SM, Eltis LD, Chambers HF, Strynadka NCJ. Structural and kinetic analyses of penicillin-binding protein 4 (PBP4)-mediated antibiotic resistance in Staphylococcus aureus. J Biol Chem 2018; 293:19854-19865. [PMID: 30366985 DOI: 10.1074/jbc.ra118.004952] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Revised: 10/24/2018] [Indexed: 01/08/2023] Open
Abstract
Methicillin-resistant Staphylococcus aureus (MRSA) causes serious community-acquired and nosocomial infections worldwide. MRSA strains are resistant to a variety of antibiotics, including the classic penicillin and cephalosporin classes of β-lactams, making them intractable to treatment. Although β-lactam resistance in MRSA has been ascribed to the acquisition and activity of penicillin-binding protein 2a (PBP2a, encoded by mecA), it has recently been observed that resistance can also be mediated by penicillin-binding protein 4 (PBP4). Previously, we have shown that broad-spectrum β-lactam resistance can arise following serial passaging of a mecA-negative COL strain of S. aureus, creating the CRB strain. This strain has two missense mutations in pbp4 and a mutation in the pbp4 promoter, both of which play an instrumental role in β-lactam resistance. To better understand PBP4's role in resistance, here we have characterized its kinetics and structure with clinically relevant β-lactam antibiotics. We present the first crystallographic PBP4 structures of apo and acyl-enzyme intermediate forms complexed with three late-generation β-lactam antibiotics: ceftobiprole, ceftaroline, and nafcillin. In parallel, we characterized the structural and kinetic effects of the PBP4 mutations present in the CRB strain. Localized within the transpeptidase active-site cleft, the two substitutions appear to have different effects depending on the drug. With ceftobiprole, the missense mutations impaired the Km value 150-fold, decreasing the proportion of inhibited PBP4. However, ceftaroline resistance appeared to be mediated by other factors, possibly including mutation of the pbp4 promoter. Our findings provide evidence that S. aureus CRB has at least two PBP4-mediated resistance mechanisms.
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Affiliation(s)
- J Andrew N Alexander
- From the Department of Biochemistry and Molecular Biology.,the Centre for Blood Research, and
| | - Som S Chatterjee
- the Division of Infectious Disease, Department of Medicine, San Francisco General Hospital, San Francisco, California 94110
| | - Stephanie M Hamilton
- the Division of Infectious Disease, Department of Medicine, San Francisco General Hospital, San Francisco, California 94110
| | - Lindsay D Eltis
- From the Department of Biochemistry and Molecular Biology.,the Department of Microbiology and Immunology, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada and
| | - Henry F Chambers
- the Division of Infectious Disease, Department of Medicine, San Francisco General Hospital, San Francisco, California 94110
| | - Natalie C J Strynadka
- From the Department of Biochemistry and Molecular Biology, .,the Centre for Blood Research, and
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8
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Park M, Rafii F. Exposure to β-lactams results in the alteration of penicillin-binding proteins in Clostridium perfringens. Anaerobe 2017; 45:78-85. [PMID: 28185856 DOI: 10.1016/j.anaerobe.2017.02.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Revised: 02/03/2017] [Accepted: 02/05/2017] [Indexed: 10/20/2022]
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9
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Bukowska-Faniband E, Hederstedt L. Transpeptidase activity of penicillin-binding protein SpoVD in peptidoglycan synthesis conditionally depends on the disulfide reductase StoA. Mol Microbiol 2017; 105:98-114. [PMID: 28383125 DOI: 10.1111/mmi.13689] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/03/2017] [Indexed: 11/28/2022]
Abstract
Endospore cortex peptidoglycan synthesis is not required for bacterial growth but essential for endospore heat resistance. It therefore constitutes an amenable system for research on peptidoglycan biogenesis. The Bacillus subtilis sporulation-specific class B penicillin-binding protein (PBP) SpoVD and many homologous PBPs contain two conserved cysteine residues of unknown function in the transpeptidase domain - one as residue x in the SxN catalytic site motif and the other in a flexible loop near the catalytic site. A disulfide bond between these residues blocks the function of SpoVD in cortex synthesis. With a combination of experiments with purified proteins and B. subtilis mutant cells, it was shown that in active SpoVD the two cysteine residues most probably interact by hydrogen bonding and that this is important for peptidoglycan synthesis in vivo. It was furthermore demonstrated that the sporulation-specific thiol-disulfide oxidoreductase StoA reduces SpoVD and that requirement of StoA for cortex synthesis can be suppressed by two completely different types of structural alterations in SpoVD. It is concluded that StoA plays a critical role mainly during maturation of SpoVD in the forespore outer membrane. The findings advance our understanding of essential PBPs and redox control of extra-cytoplasmic protein disulfides in bacterial cells.
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Affiliation(s)
- Ewa Bukowska-Faniband
- Microbiology Group, Department of Biology, Lund University, Sölvegatan 35, Lund, SE- 223 62, Sweden
| | - Lars Hederstedt
- Microbiology Group, Department of Biology, Lund University, Sölvegatan 35, Lund, SE- 223 62, Sweden
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Resistance to β-Lactams in Neisseria ssp Due to Chromosomally Encoded Penicillin-Binding Proteins. Antibiotics (Basel) 2016; 5:antibiotics5040035. [PMID: 27690121 PMCID: PMC5187516 DOI: 10.3390/antibiotics5040035] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Revised: 09/22/2016] [Accepted: 09/23/2016] [Indexed: 01/07/2023] Open
Abstract
Neisseria meningitidis and Neisseria gonorrhoeae are human pathogens that cause a variety of life-threatening systemic and local infections, such as meningitis or gonorrhoea. The treatment of such infection is becoming more difficult due to antibiotic resistance. The focus of this review is on the mechanism of reduced susceptibility to penicillin and other β-lactams due to the modification of chromosomally encoded penicillin-binding proteins (PBP), in particular PBP2 encoded by the penA gene. The variety of penA alleles and resulting variant PBP2 enzymes is described and the important amino acid substitutions are presented and discussed in a structural context.
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Glycosyltransferases and Transpeptidases/Penicillin-Binding Proteins: Valuable Targets for New Antibacterials. Antibiotics (Basel) 2016; 5:antibiotics5010012. [PMID: 27025527 PMCID: PMC4810414 DOI: 10.3390/antibiotics5010012] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Revised: 01/27/2016] [Accepted: 02/03/2016] [Indexed: 12/29/2022] Open
Abstract
Peptidoglycan (PG) is an essential macromolecular sacculus surrounding most bacteria. It is assembled by the glycosyltransferase (GT) and transpeptidase (TP) activities of multimodular penicillin-binding proteins (PBPs) within multiprotein complex machineries. Both activities are essential for the synthesis of a functional stress-bearing PG shell. Although good progress has been made in terms of the functional and structural understanding of GT, finding a clinically useful antibiotic against them has been challenging until now. In contrast, the TP/PBP module has been successfully targeted by β-lactam derivatives, but the extensive use of these antibiotics has selected resistant bacterial strains that employ a wide variety of mechanisms to escape the lethal action of these antibiotics. In addition to traditional β-lactams, other classes of molecules (non-β-lactams) that inhibit PBPs are now emerging, opening new perspectives for tackling the resistance problem while taking advantage of these valuable targets, for which a wealth of structural and functional knowledge has been accumulated. The overall evidence shows that PBPs are part of multiprotein machineries whose activities are modulated by cofactors. Perturbation of these systems could lead to lethal effects. Developing screening strategies to take advantage of these mechanisms could lead to new inhibitors of PG assembly. In this paper, we present a general background on the GTs and TPs/PBPs, a survey of recent issues of bacterial resistance and a review of recent works describing new inhibitors of these enzymes.
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12
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Antimicrobial resistance in Neisseria gonorrhoeae in the 21st century: past, evolution, and future. Clin Microbiol Rev 2015; 27:587-613. [PMID: 24982323 DOI: 10.1128/cmr.00010-14] [Citation(s) in RCA: 739] [Impact Index Per Article: 82.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Neisseria gonorrhoeae is evolving into a superbug with resistance to previously and currently recommended antimicrobials for treatment of gonorrhea, which is a major public health concern globally. Given the global nature of gonorrhea, the high rate of usage of antimicrobials, suboptimal control and monitoring of antimicrobial resistance (AMR) and treatment failures, slow update of treatment guidelines in most geographical settings, and the extraordinary capacity of the gonococci to develop and retain AMR, it is likely that the global problem of gonococcal AMR will worsen in the foreseeable future and that the severe complications of gonorrhea will emerge as a silent epidemic. By understanding the evolution, emergence, and spread of AMR in N. gonorrhoeae, including its molecular and phenotypic mechanisms, resistance to antimicrobials used clinically can be anticipated, future methods for genetic testing for AMR might permit region-specific and tailor-made antimicrobial therapy, and the design of novel antimicrobials to circumvent the resistance problems can be undertaken more rationally. This review focuses on the history and evolution of gonorrhea treatment regimens and emerging resistance to them, on genetic and phenotypic determinants of gonococcal resistance to previously and currently recommended antimicrobials, including biological costs or benefits; and on crucial actions and future advances necessary to detect and treat resistant gonococcal strains and, ultimately, retain gonorrhea as a treatable infection.
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Fedarovich A, Cook E, Tomberg J, Nicholas RA, Davies C. Structural effect of the Asp345a insertion in penicillin-binding protein 2 from penicillin-resistant strains of Neisseria gonorrhoeae. Biochemistry 2014; 53:7596-603. [PMID: 25403720 PMCID: PMC4263433 DOI: 10.1021/bi5011317] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
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A hallmark
of penicillin-binding protein 2 (PBP2) from penicillin-resistant
strains of Neisseria gonorrhoeae is insertion of
an aspartate after position 345. The insertion resides on a loop near
the active site and is immediately adjacent to an existing aspartate
(Asp346) that forms a functionally important hydrogen bond with Ser363
of the SxN conserved motif. Insertion of other amino acids, including
Glu and Asn, can also lower the rate of acylation by penicillin, but
these insertions abolish transpeptidase function. Although the kinetic
consequences of the Asp insertion are well-established, how it impacts
the structure of PBP2 is unknown. Here, we report the 2.2 Å resolution
crystal structure of a truncated construct of PBP2 containing all
five mutations present in PBP2 from the penicillin-resistant strain
6140, including the Asp insertion. Commensurate with the strict specificity
for the Asp insertion over similar amino acids, the insertion does
not cause disordering of the structure, but rather induces localized
flexibility in the β2c−β2d loop. The crystal structure
resolves the ambiguity of whether the insertion is Asp345a or Asp346a
(due to the adjacent Asp) because the hydrogen bond between Asp346
and Ser362 is preserved and the insertion is therefore Asp346a. The
side chain of Asp346a projects directly toward the β-lactam-binding
site near Asn364 of the SxN motif. The Asp insertion may lower the
rate of acylation by sterically impeding binding of the antibiotic
or by hindering breakage of the β-lactam ring during acylation
because of the negative charge of its side chain.
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Affiliation(s)
- Alena Fedarovich
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina , Charleston, South Carolina 29425, United States
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Gabani P, Prakash D, Singh OV. Emergence of antibiotic-resistant extremophiles (AREs). Extremophiles 2012; 16:697-713. [PMID: 22907125 DOI: 10.1007/s00792-012-0475-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2012] [Accepted: 08/02/2012] [Indexed: 12/14/2022]
Abstract
Excessive use of antibiotics in recent years has produced bacteria that are resistant to a wide array of antibiotics. Several genetic and non-genetic elements allow microorganisms to adapt and thrive under harsh environmental conditions such as lethal doses of antibiotics. We attempt to classify these microorganisms as antibiotic-resistant extremophiles (AREs). AREs develop strategies to gain greater resistance to antibiotics via accumulation of multiple genes or plasmids that harbor genes for multiple drug resistance (MDR). In addition to their altered expression of multiple genes, AREs also survive by producing enzymes such as penicillinase that inactivate antibiotics. It is of interest to identify the underlying molecular mechanisms by which the AREs are able to survive in the presence of wide arrays of high-dosage antibiotics. Technologically, "omics"-based approaches such as genomics have revealed a wide array of genes differentially expressed in AREs. Proteomics studies with 2DE, MALDI-TOF, and MS/MS have identified specific proteins, enzymes, and pumps that function in the adaptation mechanisms of AREs. This article discusses the molecular mechanisms by which microorganisms develop into AREs and how "omics" approaches can identify the genetic elements of these adaptation mechanisms. These objectives will assist the development of strategies and potential therapeutics to treat outbreaks of pathogenic microorganisms in the future.
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Affiliation(s)
- Prashant Gabani
- Division of Biological and Health Sciences, University of Pittsburgh, 300 Campus Drive, Bradford, PA 16701, USA
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