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Klenotic PA, Yu EW. Structural analysis of resistance-nodulation cell division transporters. Microbiol Mol Biol Rev 2024; 88:e0019823. [PMID: 38551344 DOI: 10.1128/mmbr.00198-23] [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] [Indexed: 06/28/2024] Open
Abstract
SUMMARYInfectious bacteria have both intrinsic and acquired mechanisms to combat harmful biocides that enter the cell. Through adaptive pressures, many of these pathogens have become resistant to many, if not all, of the current antibiotics used today to treat these often deadly infections. One prominent mechanism is the upregulation of efflux systems, especially the resistance-nodulation-cell division class of exporters. These tripartite systems consist of an inner membrane transporter coupled with a periplasmic adaptor protein and an outer membrane channel to efficiently transport a diverse array of substrates from inside the cell to the extracellular space. Detailed mechanistic insight into how these inner membrane transporters recognize and shuttle their substrates can ultimately inform both new antibiotic and efflux pump inhibitor design. This review examines the structural basis of substrate recognition of these pumps and the molecular mechanisms underlying multidrug extrusion, which in turn mediate antimicrobial resistance in bacterial pathogens.
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Affiliation(s)
- Philip A Klenotic
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
| | - Edward W Yu
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
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2
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Majumdar D, Philip JE, Gassoumi B, Ayachi S, Abdelaziz B, Tüzün B, Roy S. Supramolecular clumps of μ 2-1,3-acetate bridges of Cd(II)-Salen complex: Synthesis, spectroscopic characterization, crystal structure, DFT quantization's, and antifungal photodynamic therapy. Heliyon 2024; 10:e29856. [PMID: 38707382 PMCID: PMC11066650 DOI: 10.1016/j.heliyon.2024.e29856] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2024] [Revised: 04/11/2024] [Accepted: 04/16/2024] [Indexed: 05/07/2024] Open
Abstract
The article divulges the crystal growth, synthesis, and X-ray structure characterization of one centrosymmetric cadmium complex, [Cd{CdL(μ2-1,3-acetate)}2] using Salen ligand (SL). The complex is further characterized using spectroscopic and analytical techniques, including DRS, SEM-EDX, PXRD, and ICP-MS. The crystallographic study showed that the complex has a monoclinic space P21/c. Addison parameters (Ʈ) show the hexagonal geometry of the central Cd(II) metal ion. Hirshfeld surface and 2-D fingerprint confirm supramolecular contacts despite weak C-H⋯O and C-H···π interactions. Energy frameworks, FMOs, global reactivity parameters, MEP, and energy bandgap explain the complex reactivity outlook. The complex inter- and intramolecular bonding interactions were explored through natural bond orbital (NBO), QTAIM, NCI-RDG, Electron Location Function (ELF), and Localized Orbital Locator (LOL) quantization methods. In addition, the complex and its synthetic components in vitro antibacterial efficacy were investigated using Gram-positive and Gram-negative microbial strains. SAR (structure-activity relationship) correlates with biological potency. Molecular docking assessed antimicrobial potency with proteins S. aureus (PDB ID: 1JIJ), C. albicans (PDB ID: 1M7A), E. coli (PDB ID: 1T9U), P. aeruginosa (PDB ID: 2UV0), and A. Niger (PDB ID: 3K4P). The findings are backed by the Protein-Ligand Interaction Profiler (PLIP). The antifungal potency and cell viability test of C. albicans were conducted using photodynamic therapy (APDT).
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Affiliation(s)
- Dhrubajyoti Majumdar
- Department of Chemistry, Tamralipta Mahavidyalaya, Tamluk, 721636, West Bengal, India
| | | | - Bouzid Gassoumi
- Laboratory of Advanced Materials and Interfaces (LIMA), University of Monastir, Faculty of Sciences of Monastir, Avenue of Environment, 5000, Monastir, Tunisia
| | - Sahbi Ayachi
- Laboratory of Physico-Chemistry of Materials (LR01ES19), Faculty of Sciences, Avenue of the Environment 5019 Monastir, University of Monastir, Tunisia
| | - Balkis Abdelaziz
- Laboratory of Physico-Chemistry of Materials (LR01ES19), Faculty of Sciences, Avenue of the Environment 5019 Monastir, University of Monastir, Tunisia
| | - Burak Tüzün
- Sivas Cumhuriyet University, Sivas Vocational School, Department of Plant and Animal Production, TR-58140, Sivas, Turkey
| | - Sourav Roy
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, 560012, India
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3
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Hamami E, Huo W, Hernandez-Bird J, Castaneda A, Bai J, Syal S, Ortiz-Marquez JC, van Opijnen T, Geisinger E, Isberg RR. Identification of Determinants that Allow Maintenance of High-Level Fluoroquinolone Resistance in Acinetobacter baumannii. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.10.03.560562. [PMID: 38645180 PMCID: PMC11030222 DOI: 10.1101/2023.10.03.560562] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/23/2024]
Abstract
Acinetobacter baumannii is associated with multidrug resistant (MDR) infections in healthcare settings, with fluoroquinolones such as ciprofloxacin being currently ineffective. Clinical isolates largely harbor mutations in the GyrA and TopoIV fluoroquinolone targets, as well as mutations that increase expression of drug resistance-nodulation-division (RND) efflux pumps. Factors critical for maintaining fitness levels of pump overproducers are uncharacterized despite their prevalence in clinical isolates. We here identify proteins that contribute to the fitness of FQR strains overexpressing three known RND systems using high-density insertion mutagenesis. Overproduction of the AdeFGH efflux pump caused hypersensitization to defects in outer membrane homeostatic regulation, including lesions that reduced LOS biosynthesis and blocked production of the major A. baumannii porin. In contrast, AdeAB pump overproduction, which does not affect the outer membrane pump component, was relatively tolerant to loss of these functions, consistent with outer membrane protein overproduction being the primary disruptive component. Surprisingly, overproduction of proton-transporting efflux pumps had little impact on cytosolic pH, consistent with a compensatory response to pump activity. The most striking transcriptional changes were associated with AdeFGH pump overproduction, resulting in activation of the phenylacetate (PAA) degradation regulon. Disruption of the PAA pathway resulted in cytosolic acidification and defective expression of genes involved in protection from peroxide stress. These results indicate that the RND outer membrane protein overproduction is compensated by cytoplasmic buffering and maintenance of outer membrane integrity in A. baumannii to facilitate fitness of FQR isolates.
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Affiliation(s)
- Efrat Hamami
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 150 Harrison Ave., Boston, MA 02111, USA
| | - Wenwen Huo
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 150 Harrison Ave., Boston, MA 02111, USA
| | - Juan Hernandez-Bird
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 150 Harrison Ave., Boston, MA 02111, USA
| | | | - Jinna Bai
- Department of Biology, Northeastern University, Boston, MA 02115, USA
| | - Sapna Syal
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 150 Harrison Ave., Boston, MA 02111, USA
| | - Juan C Ortiz-Marquez
- Department of Biology, Boston College, Chestnut Hill, MA 02135 USA
- Innovation Laboratory, Broad Institute, Cambridge, MA 02412, USA
| | - Tim van Opijnen
- Innovation Laboratory, Broad Institute, Cambridge, MA 02412, USA
| | - Edward Geisinger
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 150 Harrison Ave., Boston, MA 02111, USA
- Department of Biology, Northeastern University, Boston, MA 02115, USA
| | - Ralph R Isberg
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 150 Harrison Ave., Boston, MA 02111, USA
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Wilhelm J, Pos KM. Molecular insights into the determinants of substrate specificity and efflux inhibition of the RND efflux pumps AcrB and AdeB. MICROBIOLOGY (READING, ENGLAND) 2024; 170:001438. [PMID: 38358391 PMCID: PMC10924465 DOI: 10.1099/mic.0.001438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Accepted: 01/30/2024] [Indexed: 02/16/2024]
Abstract
Gram-negative bacterial members of the Resistance Nodulation and cell Division (RND) superfamily form tripartite efflux pump systems that span the cell envelope. One of the intriguing features of the multiple drug efflux members of this superfamily is their ability to recognize different classes of antibiotics, dyes, solvents, bile salts, and detergents. This review provides an overview of the molecular mechanisms of multiple drug efflux catalysed by the tripartite RND efflux system AcrAB-TolC from Eschericha coli. The determinants for sequential or simultaneous multiple substrate binding and efflux pump inhibitor binding are discussed. A comparison is made with the determinants for substrate binding of AdeB from Acinetobacter baumannii, which acts within the AdeABC multidrug efflux system. There is an apparent general similarity between the structures of AcrB and AdeB and their substrate specificity. However, the presence of distinct conformational states and different drug efflux capacities as revealed by single-particle cryo-EM and mutational analysis suggest that the drug binding and transport features exhibited by AcrB may not be directly extrapolated to the homolog AdeB efflux pump.
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Affiliation(s)
- Julia Wilhelm
- Institute of Biochemistry, Goethe-University Frankfurt, Max-von-Laue-Str. 9, D-60438 Frankfurt am Main, Germany
| | - Klaas Martinus Pos
- Institute of Biochemistry, Goethe-University Frankfurt, Max-von-Laue-Str. 9, D-60438 Frankfurt am Main, Germany
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Allgood SC, Su CC, Crooks AL, Meyer CT, Zhou B, Betterton MD, Barbachyn MR, Yu EW, Detweiler CS. Bacterial efflux pump modulators prevent bacterial growth in macrophages and under broth conditions that mimic the host environment. mBio 2023; 14:e0249223. [PMID: 37921493 PMCID: PMC10746280 DOI: 10.1128/mbio.02492-23] [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: 09/19/2023] [Accepted: 09/21/2023] [Indexed: 11/04/2023] Open
Abstract
IMPORTANCE Bacterial efflux pumps are critical for resistance to antibiotics and for virulence. We previously identified small molecules that inhibit efflux pumps (efflux pump modulators, EPMs) and prevent pathogen replication in host cells. Here, we used medicinal chemistry to increase the activity of the EPMs against pathogens in cells into the nanomolar range. We show by cryo-electron microscopy that these EPMs bind an efflux pump subunit. In broth culture, the EPMs increase the potency (activity), but not the efficacy (maximum effect), of antibiotics. We also found that bacterial exposure to the EPMs appear to enable the accumulation of a toxic metabolite that would otherwise be exported by efflux pumps. Thus, inhibitors of bacterial efflux pumps could interfere with infection not only by potentiating antibiotics, but also by allowing toxic waste products to accumulate within bacteria, providing an explanation for why efflux pumps are needed for virulence in the absence of antibiotics.
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Affiliation(s)
- Samual C. Allgood
- Molecular, Cellular, and Developmental Biology, University of Colorado Boulder, Boulder, Colorado, USA
| | - Chih-Chia Su
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
- Cleveland Center for Membrane and Structural Biology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
| | - Amy L. Crooks
- Molecular, Cellular, and Developmental Biology, University of Colorado Boulder, Boulder, Colorado, USA
| | - Christian T. Meyer
- Molecular, Cellular, and Developmental Biology, University of Colorado Boulder, Boulder, Colorado, USA
- Chemical and Biological Engineering, University of Colorado Boulder, Boulder, Colorado, USA
- Duet Biosystems, Nashville, Tennessee, USA
- Antimicrobial Research Consortium (ARC) Labs, Boulder, Colorado, USA
| | - Bojun Zhou
- Department of Physics, University of Colorado, Boulder, Colorado, USA
| | - Meredith D. Betterton
- Molecular, Cellular, and Developmental Biology, University of Colorado Boulder, Boulder, Colorado, USA
- Department of Physics, University of Colorado, Boulder, Colorado, USA
- Center for Computational Biology, Flatiron Institute, New York, New York, USA
| | | | - Edward W. Yu
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
- Cleveland Center for Membrane and Structural Biology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
| | - Corrella S. Detweiler
- Molecular, Cellular, and Developmental Biology, University of Colorado Boulder, Boulder, Colorado, USA
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Allgood SC, Su CC, Crooks AL, Meyer CT, Zhou B, Betterton MD, Barbachyn MR, Yu EW, Detweiler CS. Bacterial Efflux Pump Modulators Prevent Bacterial Growth in Macrophages and Under Broth Conditions that Mimic the Host Environment. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.20.558466. [PMID: 37786697 PMCID: PMC10541609 DOI: 10.1101/2023.09.20.558466] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/04/2023]
Abstract
New approaches for combatting microbial infections are needed. One strategy for disrupting pathogenesis involves developing compounds that interfere with bacterial virulence. A critical molecular determinant of virulence for Gram-negative bacteria are efflux pumps of the resistance-nodulation-division (RND) family, which includes AcrAB-TolC. We previously identified small molecules that bind AcrB, inhibit AcrAB-TolC, and do not appear to damage membranes. These efflux pump modulators (EPMs) were discovered in an in-cell screening platform called SAFIRE (Screen for Anti-infectives using Fluorescence microscopy of IntracellulaR Enterobacteriaceae). SAFIRE identifies compounds that disrupt the growth of a Gram-negative human pathogen, Salmonella enterica serotype Typhimurium (S. Typhimurium) in macrophages. We used medicinal chemistry to iteratively design ~200 EPM35 analogs and test them for activity in SAFIRE, generating compounds with nanomolar potency. Analogs were demonstrated to bind AcrB in a substrate binding pocket by cryo-electron microscopy (cryo-EM). Despite having amphipathic structures, the EPM analogs do not disrupt membrane voltage, as monitored by FtsZ localization to the cell septum. The EPM analogs had little effect on bacterial growth in standard Mueller Hinton Broth. However, under broth conditions that mimic the micro-environment of the macrophage phagosome, acrAB is required for growth, the EPM analogs are bacteriostatic, and increase the potency of antibiotics. These data suggest that under macrophage-like conditions the EPM analogs prevent the export of a toxic bacterial metabolite(s) through AcrAB-TolC. Thus, compounds that bind AcrB could disrupt infection by specifically interfering with the export of bacterial toxic metabolites, host defense factors, and/or antibiotics.
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Affiliation(s)
- Samual C Allgood
- Molecular, Cellular Developmental Biology, University of Colorado Boulder, Boulder, CO, USA
| | - Chih-Chia Su
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
- Cleveland Center for Membrane and Structural Biology, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Amy L Crooks
- Molecular, Cellular Developmental Biology, University of Colorado Boulder, Boulder, CO, USA
| | - Christian T Meyer
- Molecular, Cellular Developmental Biology, University of Colorado Boulder, Boulder, CO, USA
- Chemical and Biological Engineering, University of Colorado Boulder, Boulder, CO, USA
- Duet Biosystems, Nashville, TN, USA
- Antimicrobial Research Consortium (ARC) Labs, Boulder, CO, USA
| | - Bojun Zhou
- Department of Physics, University of Colorado, Boulder, CO, USA
| | - Meredith D Betterton
- Molecular, Cellular Developmental Biology, University of Colorado Boulder, Boulder, CO, USA
- Department of Physics, University of Colorado, Boulder, CO, USA
- Center for Computational Biology, Flatiron Institute, New York, NY, USA
| | | | - Edward W Yu
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
- Cleveland Center for Membrane and Structural Biology, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Corrella S Detweiler
- Molecular, Cellular Developmental Biology, University of Colorado Boulder, Boulder, CO, USA
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Hasan M, Wang J, Ahn J. Ciprofloxacin and Tetracycline Resistance Cause Collateral Sensitivity to Aminoglycosides in Salmonella Typhimurium. Antibiotics (Basel) 2023; 12:1335. [PMID: 37627755 PMCID: PMC10451331 DOI: 10.3390/antibiotics12081335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2023] [Revised: 08/09/2023] [Accepted: 08/16/2023] [Indexed: 08/27/2023] Open
Abstract
The objective of this study was to evaluate collateral sensitivity and cross-resistance of antibiotic-induced resistant Salmonella Typhimurium to various antibiotics. S. Typhimurium ATCC 19585 (STWT) was exposed to ciprofloxacin, gentamicin, kanamycin, and tetracycline to induce antibiotic resistance, respectively, assigned as STCIP, STGEN, STKAN, and STTET. The susceptibilities of the antibiotic-induced resistant mutants to cefotaxime, chloramphenicol, ciprofloxacin, gentamicin, kanamycin, polymyxin B, streptomycin, tetracycline, and tobramycin were determined in the absence and presence of CCCP and PAβN. STCIP showed the cross-resistance to tetracycline and collateral sensitivity to gentamicin (1/2 fold) and kanamycin (1/4 fold). STTET was also cross-resistant to ciprofloxacin (128-fold) and collateral sensitive to gentamicin (1/4-fold) and kanamycin (1/8-fold). The cross-resistance and collateral sensitivity of STCIP and STTET were associated with the AcrAB-TolC efflux pump and outer membrane porin proteins (OmpC). This study provides new insight into the collateral sensitivity phenomenon, which can be used for designing effective antibiotic treatment regimens to control antibiotic-resistant bacteria.
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Affiliation(s)
- Mahadi Hasan
- Department of Biomedical Science, Kangwon National University, Chuncheon 24341, Gangwon, Republic of Korea;
| | - Jun Wang
- College of Food Science and Engineering, Qingdao Agricultural University, Qingdao 266109, China;
| | - Juhee Ahn
- Department of Biomedical Science, Kangwon National University, Chuncheon 24341, Gangwon, Republic of Korea;
- Institute of Bioscience and Biotechnology, Kangwon National University, Chuncheon 24341, Gangwon, Republic of Korea
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8
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Zhang Z, Lizer N, Wu Z, Morgan CE, Yan Y, Zhang Q, Yu EW. Cryo-Electron Microscopy Structures of a Campylobacter Multidrug Efflux Pump Reveal a Novel Mechanism of Drug Recognition and Resistance. Microbiol Spectr 2023; 11:e0119723. [PMID: 37289051 PMCID: PMC10434076 DOI: 10.1128/spectrum.01197-23] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Accepted: 05/18/2023] [Indexed: 06/09/2023] Open
Abstract
Campylobacter jejuni is a bacterium that is commonly present in the intestinal tracts of animals. It is also a major foodborne pathogen that causes gastroenteritis in humans. The most predominant and clinically important multidrug efflux system in C. jejuni is the CmeABC (Campylobacter multidrug efflux) pump, a tripartite system that includes an inner membrane transporter (CmeB), a periplasmic fusion protein (CmeA), and an outer membrane channel protein (CmeC). This efflux protein machinery mediates resistance to a number of structurally diverse antimicrobial agents. A recently identified CmeB variant, termed resistance enhancing CmeB (RE-CmeB), can increase its multidrug efflux pump activity, likely by influencing antimicrobial recognition and extrusion. Here, we report structures of RE-CmeB in its apo form as well as in the presence of four different drugs by using single-particle cryo-electron microscopy (cryo-EM). Coupled with mutagenesis and functional studies, this structural information allows us to identify critical amino acids that are important for drug resistance. We also report that RE-CmeB utilizes a somewhat unique subset of residues to bind different drugs, thereby optimizing its ability to accommodate different compounds with distinct scaffolds. These findings provide insights into the structure-function relationship of this newly emerged antibiotic efflux transporter variant in Campylobacter. IMPORTANCE Campylobacter jejuni has emerged as one of the most problematic and highly antibiotic-resistant pathogens, worldwide. The Centers for Disease Control and Prevention have designated antibiotic-resistant C. jejuni as a serious antibiotic resistance threat in the United States. We recently identified a C. jejuni resistance enhancing CmeB (RE-CmeB) variant that can increase its multidrug efflux pump activity and confers an exceedingly high-level of resistance to fluoroquinolones. Here, we report the cryo-EM structures of this prevalent and clinically important C. jejuni RE-CmeB multidrug efflux pump in both the absence and presence of four antibiotics. These structures allow us to understand the action mechanism for multidrug recognition in this pump. Our studies will ultimately inform an era in structure-guided drug design to combat multidrug resistance in these Gram-negative pathogens.
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Affiliation(s)
- Zhemin Zhang
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
| | - Nicholas Lizer
- Department of Veterinary Microbiology, College of Veterinary Medicine, Iowa State University, Ames, Iowa, USA
| | - Zuowei Wu
- Department of Veterinary Microbiology, College of Veterinary Medicine, Iowa State University, Ames, Iowa, USA
| | - Christopher E. Morgan
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
| | - Yuqi Yan
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
| | - Qijing Zhang
- Department of Veterinary Microbiology, College of Veterinary Medicine, Iowa State University, Ames, Iowa, USA
| | - Edward W. Yu
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
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Avakh A, Grant GD, Cheesman MJ, Kalkundri T, Hall S. The Art of War with Pseudomonas aeruginosa: Targeting Mex Efflux Pumps Directly to Strategically Enhance Antipseudomonal Drug Efficacy. Antibiotics (Basel) 2023; 12:1304. [PMID: 37627724 PMCID: PMC10451789 DOI: 10.3390/antibiotics12081304] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Revised: 07/26/2023] [Accepted: 08/07/2023] [Indexed: 08/27/2023] Open
Abstract
Pseudomonas aeruginosa (P. aeruginosa) poses a grave clinical challenge due to its multidrug resistance (MDR) phenotype, leading to severe and life-threatening infections. This bacterium exhibits both intrinsic resistance to various antipseudomonal agents and acquired resistance against nearly all available antibiotics, contributing to its MDR phenotype. Multiple mechanisms, including enzyme production, loss of outer membrane proteins, target mutations, and multidrug efflux systems, contribute to its antimicrobial resistance. The clinical importance of addressing MDR in P. aeruginosa is paramount, and one pivotal determinant is the resistance-nodulation-division (RND) family of drug/proton antiporters, notably the Mex efflux pumps. These pumps function as crucial defenders, reinforcing the emergence of extensively drug-resistant (XDR) and pandrug-resistant (PDR) strains, which underscores the urgency of the situation. Overcoming this challenge necessitates the exploration and development of potent efflux pump inhibitors (EPIs) to restore the efficacy of existing antipseudomonal drugs. By effectively countering or bypassing efflux activities, EPIs hold tremendous potential for restoring the antibacterial activity against P. aeruginosa and other Gram-negative pathogens. This review focuses on concurrent MDR, highlighting the clinical significance of efflux pumps, particularly the Mex efflux pumps, in driving MDR. It explores promising EPIs and delves into the structural characteristics of the MexB subunit and its substrate binding sites.
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Affiliation(s)
| | | | | | | | - Susan Hall
- School of Pharmacy and Medical Sciences, Griffith University, Gold Coast, QLD 4222, Australia; (A.A.); (G.D.G.); (M.J.C.); (T.K.)
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10
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Trampari E, Prischi F, Vargiu AV, Abi-Assaf J, Bavro VN, Webber MA. Functionally distinct mutations within AcrB underpin antibiotic resistance in different lifestyles. NPJ ANTIMICROBIALS AND RESISTANCE 2023; 1:2. [PMID: 38686215 PMCID: PMC11057200 DOI: 10.1038/s44259-023-00001-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Accepted: 02/27/2023] [Indexed: 05/02/2024]
Abstract
Antibiotic resistance is a pressing healthcare challenge and is mediated by various mechanisms, including the active export of drugs via multidrug efflux systems, which prevent drug accumulation within the cell. Here, we studied how Salmonella evolved resistance to two key antibiotics, cefotaxime and azithromycin, when grown planktonically or as a biofilm. Resistance to both drugs emerged in both conditions and was associated with different substitutions within the efflux-associated transporter, AcrB. Azithromycin exposure selected for an R717L substitution, while cefotaxime for Q176K. Additional mutations in ramR or envZ accumulated concurrently with the R717L or Q176K substitutions respectively, resulting in clinical resistance to the selective antibiotics and cross-resistance to other drugs. Structural, genetic, and phenotypic analysis showed the two AcrB substitutions confer their benefits in profoundly different ways. R717L reduces steric barriers associated with transit through the substrate channel 2 of AcrB. Q176K increases binding energy for cefotaxime, improving recognition in the distal binding pocket, resulting in increased efflux efficiency. Finally, we show the R717 substitution is present in isolates recovered around the world.
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Affiliation(s)
- Eleftheria Trampari
- Quadram Institute Bioscience, Norwich Research Park, Norwich, Norfolk NR4 7UQ UK
| | - Filippo Prischi
- School of Life Sciences, University of Essex, Wivenhoe Park, Colchester, CO4 3SQ UK
| | - Attilio V. Vargiu
- Department of Physics, University of Cagliari, S. P. 8, km. 0.700, 09042 Monserrato, Italy
| | - Justin Abi-Assaf
- Quadram Institute Bioscience, Norwich Research Park, Norwich, Norfolk NR4 7UQ UK
| | - Vassiliy N. Bavro
- School of Life Sciences, University of Essex, Wivenhoe Park, Colchester, CO4 3SQ UK
| | - Mark A. Webber
- Quadram Institute Bioscience, Norwich Research Park, Norwich, Norfolk NR4 7UQ UK
- Medical School, University of East Anglia, Norwich Research Park, Norwich, Norfolk NR4 7UA UK
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11
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Athar M, Gervasoni S, Catte A, Basciu A, Malloci G, Ruggerone P, Vargiu AV. Tripartite efflux pumps of the RND superfamily: what did we learn from computational studies? MICROBIOLOGY (READING, ENGLAND) 2023; 169. [PMID: 36972322 DOI: 10.1099/mic.0.001307] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/29/2023]
Abstract
Bacterial resistance to antibiotics has been long recognized as a priority to address for human health. Among all micro-organisms, the so-called multi-drug resistant (MDR) bacteria, which are resistant to most, if not all drugs in our current arsenal, are particularly worrisome. The World Health Organization has prioritized the ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter species) pathogens, which include four Gram-negative bacterial species. In these bacteria, active extrusion of antimicrobial compounds out of the cell by means of 'molecular guns' known as efflux pumps is a main determinant of MDR phenotypes. The resistance-nodulation-cell division (RND) superfamily of efflux pumps connecting the inner and outer membrane in Gram-negative bacteria is crucial to the onset of MDR and virulence, as well as biofilm formation. Thus, understanding the molecular basis of the interaction of antibiotics and inhibitors with these pumps is key to the design of more effective therapeutics. With the aim to contribute to this challenge, and complement and inspire experimental research, in silico studies on RND efflux pumps have flourished in recent decades. Here, we review a selection of such investigations addressing the main determinants behind the polyspecificity of these pumps, the mechanisms of substrate recognition, transport and inhibition, as well as the relevance of their assembly for proper functioning, and the role of protein-lipid interactions. The journey will end with a perspective on the role of computer simulations in addressing the challenges posed by these beautifully complex machineries and in supporting the fight against the spread of MDR bacteria.
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Affiliation(s)
- Mohd Athar
- Physics Department, University of Cagliari, Cittadella Universitaria, SP 8 km 0.700, 09042, Monserrato (CA), Italy
| | - Silvia Gervasoni
- Physics Department, University of Cagliari, Cittadella Universitaria, SP 8 km 0.700, 09042, Monserrato (CA), Italy
| | - Andrea Catte
- Physics Department, University of Cagliari, Cittadella Universitaria, SP 8 km 0.700, 09042, Monserrato (CA), Italy
| | - Andrea Basciu
- Physics Department, University of Cagliari, Cittadella Universitaria, SP 8 km 0.700, 09042, Monserrato (CA), Italy
| | - Giuliano Malloci
- Physics Department, University of Cagliari, Cittadella Universitaria, SP 8 km 0.700, 09042, Monserrato (CA), Italy
| | - Paolo Ruggerone
- Physics Department, University of Cagliari, Cittadella Universitaria, SP 8 km 0.700, 09042, Monserrato (CA), Italy
| | - Attilio Vittorio Vargiu
- Physics Department, University of Cagliari, Cittadella Universitaria, SP 8 km 0.700, 09042, Monserrato (CA), Italy
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12
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Cryo-EM Structures of AcrD Illuminate a Mechanism for Capturing Aminoglycosides from Its Central Cavity. mBio 2023; 14:e0338322. [PMID: 36625574 PMCID: PMC9973356 DOI: 10.1128/mbio.03383-22] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The Escherichia coli acriflavine resistance protein D (AcrD) is an efflux pump that belongs to the resistance-nodulation-cell division (RND) superfamily. Its primary function is to provide resistance to aminoglycoside-based drugs by actively extruding these noxious compounds out of E. coli cells. AcrD can also mediate resistance to a limited range of other amphiphilic agents, including bile acids, novobiocin, and fusidic acids. As there is no structural information available for any aminoglycoside-specific RND pump, here we describe cryo-electron microscopy (cryo-EM) structures of AcrD in the absence and presence of bound gentamicin. These structures provide new information about the RND superfamily of efflux pumps, specifically, that three negatively charged residues central to the aminoglycoside-binding site are located within the ceiling of the central cavity of the AcrD trimer. Thus, it is likely that AcrD is capable of picking up aminoglycosides via this central cavity. Through the combination of cryo-EM structural determination, mutagenesis analysis, and molecular simulation, we show that charged residues are critically important for this pump to shuttle drugs directly from the central cavity to the funnel of the AcrD trimer for extrusion. IMPORTANCE Here, we report cryo-EM structures of the AcrD aminoglycoside efflux pump in the absence and presence of bound gentamicin, posing the possibility that this pump is capable of capturing aminoglycosides from the central cavity of the AcrD trimer. The results indicate that AcrD utilizes charged residues to bind and export drugs, mediating resistance to these antibiotics.
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13
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Sodium Malonate Inhibits the AcrAB-TolC Multidrug Efflux Pump of Escherichia coli and Increases Antibiotic Efficacy. Pathogens 2022; 11:pathogens11121409. [PMID: 36558743 PMCID: PMC9781404 DOI: 10.3390/pathogens11121409] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Revised: 11/11/2022] [Accepted: 11/21/2022] [Indexed: 11/25/2022] Open
Abstract
There is an urgent need to find novel treatments for combating multidrug-resistant bacteria. Multidrug efflux pumps that expel antibiotics out of cells are major contributors to this problem. Therefore, using efflux pump inhibitors (EPIs) is a promising strategy to increase antibiotic efficacy. However, there are no EPIs currently approved for clinical use especially because of their toxicity. This study investigates sodium malonate, a natural, non-hazardous, small molecule, for its use as a novel EPI of AcrAB-TolC, the main multidrug efflux pump of the Enterobacteriaceae family. Using ethidium bromide accumulation experiments, we found that 25 mM sodium malonate inhibited efflux by the AcrAB-TolC and other MDR pumps of Escherichia coli to a similar degree than 50 μΜ phenylalanine-arginine-β-naphthylamide, a well-known EPI. Using minimum inhibitory concentration assays and molecular docking to study AcrB-ligand interactions, we found that sodium malonate increased the efficacy of ethidium bromide and the antibiotics minocycline, chloramphenicol, and ciprofloxacin, possibly via binding to multiple AcrB locations, including the AcrB proximal binding pocket. In conclusion, sodium malonate is a newly discovered EPI that increases antibiotic efficacy. Our findings support the development of malonic acid/sodium malonate and its derivatives as promising EPIs for augmenting antibiotic efficacy when treating multidrug-resistant bacterial infections.
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14
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Structural Basis of Peptide-Based Antimicrobial Inhibition of a Resistance-Nodulation-Cell Division Multidrug Efflux Pump. Microbiol Spectr 2022; 10:e0299022. [PMID: 36121287 PMCID: PMC9603588 DOI: 10.1128/spectrum.02990-22] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Bacterial efflux pumps in the resistance-nodulation-cell division (RND) family of Gram-negative bacteria contribute significantly to the development of antimicrobial resistance by many pathogens. In this study, we selected the MtrD transporter protein of Neisseria gonorrhoeae as it is the sole RND pump possessed by this strictly human pathogen and can export multiple antimicrobials, including antibiotics, bile salts, detergents, dyes, and antimicrobial peptides. Using knowledge from our previously published structures of MtrD in the presence or absence of bound antibiotics as a model and the known ability of MtrCDE to export cationic antimicrobial peptides, we hypothesized that cationic peptides could be accommodated within MtrD binding sites. Furthermore, we thought that MtrD-bound peptides lacking antibacterial action could sensitize bacteria to an antibiotic normally exported by the MtrCDE efflux pump or other similar RND-type pumps possessed by different Gram-negative bacteria. We now report the identification of a novel nonantimicrobial cyclic cationic antimicrobial peptide, which we termed CASP (cationic antibiotic-sensitizing peptide). By single-particle cryo-electron microscopy, we found that CASP binds within the periplasmic cleft region of MtrD using overlapping and distinct amino acid contact sites that interact with another cyclic peptide (colistin) or a linear human cationic antimicrobial peptide derived from human LL-37. While CASP could not sensitize Neisseria gonorrhoeae to an antibiotic (novobiocin) that is a substrate for RND pumps, it could do so against multiple Gram-negative, rod-shaped bacteria. We propose that CASP (or future derivatives) could serve as an adjuvant for the antibiotic treatment of certain Gram-negative infections previously thwarted by RND transporters. IMPORTANCE RND efflux pumps can export numerous antimicrobials that enter Gram-negative bacteria, and their action can reduce the efficacy of antibiotics and provide decreased susceptibility to various host antimicrobials. Here, we identified a cationic antibiotic-sensitizing peptide (CASP) that binds within the periplasmic cleft of an RND transporter protein (MtrD) produced by Neisseria gonorrhoeae. Surprisingly, CASP was able to render rod-shaped Gram-negative bacteria, but not gonococci, susceptible to an antibiotic that is a substrate for the gonococcal MtrCDE efflux pump. CASP (or its future derivatives) could be used as an adjuvant to treat infections for which RND efflux contributes to multidrug resistance.
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15
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Ren Z, Zhao Y, Huang J, Han S, Wang Y. Validation and inhibition study for toxic expression of quinolone antibiotic resistance genes in agricultural soils of eastern China. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2022; 241:113806. [PMID: 35753276 DOI: 10.1016/j.ecoenv.2022.113806] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 06/18/2022] [Accepted: 06/21/2022] [Indexed: 06/15/2023]
Abstract
With the extensive use of antibiotics, the problem of antibiotic resistance genes (ARGs) has gradually emerged. As agricultural soil is an important enrichment media of antibiotics and ARGs, it is particularly important to study the toxicity of ARGs, the effects of various nutrients and pollutants, and how to control them through source modification and process regulation. In this study, a combination of source modification and process regulation was used to weaken the toxic expression of Quinolones' (QNs') ARGs in soils from different agricultural areas. And the influence of soil nutrients and pollutants on this process will be explored. Protein-protein docking and molecular docking were used to construct a target protein complex for the toxic expression of QNs' ARGs and characterize the toxicity of QNs' ARGs. The two-dimensional and three-dimensional quantitative structure-activity relationships model construction and sensitivity analysis were used to molecular modification and related validation. Molecular dynamics simulations assisted by sampling survey method based on agricultural soils in Northeast China and the lower-middle reaches of the Yangtze River were carried out to generate four scenarios. The main results are: (a) A functionally improved and environmentally friendly quinolone derivative (ORB-19) was designed. It can effectively inhibit the expression of QNs' ARGs and weaken the antibiotic selection pressure risk. The application of ORB-19 in agricultural areas could significantly inhibit the toxic expression of QNs' ARGs (112.75%~169.59%); (b) QNs' ARGs have a stronger toxic expression in agricultural areas of Northeast China, which have higher nutrient elements; (c) The contribution of different types of agricultural pollution to suppressing the toxic expression of QNs' ARGs in agricultural soils varies; (d) The options of applied field measures given for the inhibition of QNs' ARG toxic expression varied between plots with different agricultural pollution types. This study provides theoretical support for inhibiting the toxic expression of QNs' ARGs in the soil environment, reducing the spread of ARGs in microbial populations, replacing green QNs derivatives, and sustainable development of agricultural soils.
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Affiliation(s)
- Zhixing Ren
- College of Forestry, Northeast Forestry University, Harbin 150040, China.
| | - Yuanyuan Zhao
- MOE Key Laboratory of Resources and Environmental Systems Optimization, North China Electric Power University, Beijing 102206, China.
| | - Jin Huang
- College of Materials Science and Chemical Engineering, Harbin Engineering University, Harbin 150001, China.
| | - Song Han
- College of Forestry, Northeast Forestry University, Harbin 150040, China.
| | - Yingwei Wang
- College of Forestry, Northeast Forestry University, Harbin 150040, China.
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16
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Differential Binding of Carbapenems with the AdeABC Efflux Pump and Modulation of the Expression of AdeB Linked to Novel Mutations within Two-Component System AdeRS in Carbapenem-Resistant Acinetobacter baumannii. mSystems 2022; 7:e0021722. [PMID: 35735748 PMCID: PMC9426577 DOI: 10.1128/msystems.00217-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Resistance-nodulation-division-type efflux system AdeABC plays an important role in carbapenem resistance among Acinetobacter baumannii. However, a knowledge gap is observed regarding the role of its regulator AdeRS in carbapenem-resistant A. baumannii (CRAB). This study effectively combines microbiological analysis with an in-silico structural approach to understand the contribution of AdeRS among CRAB (n = 38). Additionally, molecular docking was performed for the first time to study the interaction of FDA-approved carbapenems and pump inhibitor PAβN with the open and closed structure of AdeB at the three binding sites (periplasmic, proximal, distal). It was observed that open conformation of AdeB facilitates the binding of carbapenems and PAβN at entrance and proximal sites compared to the closed conformation. PAβN was found to block carbapenem interacting residues in AdeB, establishing its role as a competitive inhibitor of AdeB substrates. Overexpression of AdeABC was detected by q-RT-PCR among 29% of CRABs, and several mutations within AdeS (GLY186VAL, SER188PHE, GLU121LYS, VAL255ILE) and AdeR (VAL120ILE, ALA136VAL) were detected by sequencing. The sequence and structure-based study of AdeRS was performed to analyze the probable effect of these mutations on regulation of the two-component system (TCS), especially, utilizing its three-dimensional structure. AdeS mutations inhibited the transfer of a phosphate group to AdeR, preventing the binding of AdeR to the intercistronic region, leading to overexpression of AdeABC. The elucidation of the role of mutations in AdeRS improves our understanding of TCS-based regulation. Identification of the key residues of AdeB interacting with carbapenems and PAβN may help in future designing of novel inhibitors. IMPORTANCE AdeABC is an important efflux pump in A. baumannii that plays a role in resistance toward different antibiotics including the “last resort” antibiotic, carbapenem. This pump is regulated by a two-component system, AdeRS. To understand the binding of carbapenems with AdeABC and pump inhibition by PAβN, we analyzed for the first time the possible atomic level interactions of carbapenems and PAβN with AdeB. In the current study, AdeRS-associated novel mutations in clinical A. baumannii are reported for the first time, and a sequence-structure based in-silico approach was used to interpret their role in AdeABC overexpression, leading to carbapenem resistance. None of the previous studies had undertaken both these aspects simultaneously. This study analyzes the open and closed conformation of AdeB, their binding with carbapenems, and key residues involved in it. This helps in visualizing the plausible atomic level causes of pump inhibition driving the discovery of novel inhibitors.
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17
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Sharkey RE, Herbert JB, McGaha DA, Nguyen V, Schoeffler AJ, Dunkle JA. Three critical regions of the erythromycin resistance methyltransferase, ErmE, are required for function supporting a model for the interaction of Erm family enzymes with substrate rRNA. RNA (NEW YORK, N.Y.) 2022; 28:210-226. [PMID: 34795028 PMCID: PMC8906542 DOI: 10.1261/rna.078946.121] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Accepted: 10/23/2021] [Indexed: 06/13/2023]
Abstract
6-Methyladenosine modification of DNA and RNA is widespread throughout the three domains of life and often accomplished by a Rossmann-fold methyltransferase domain which contains conserved sequence elements directing S-adenosylmethionine cofactor binding and placement of the target adenosine residue into the active site. Elaborations to the conserved Rossman-fold and appended domains direct methylation to diverse DNA and RNA sequences and structures. Recently, the first atomic-resolution structure of a ribosomal RNA adenine dimethylase (RRAD) family member bound to rRNA was solved, TFB1M bound to helix 45 of 12S rRNA. Since erythromycin resistance methyltransferases are also members of the RRAD family, and understanding how these enzymes recognize rRNA could be used to combat their role in antibiotic resistance, we constructed a model of ErmE bound to a 23S rRNA fragment based on the TFB1M-rRNA structure. We designed site-directed mutants of ErmE based on this model and assayed the mutants by in vivo phenotypic assays and in vitro assays with purified protein. Our results and additional bioinformatic analyses suggest our structural model captures key ErmE-rRNA interactions and indicate three regions of Erm proteins play a critical role in methylation: the target adenosine binding pocket, the basic ridge, and the α4-cleft.
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Affiliation(s)
- Rory E Sharkey
- Department of Chemistry and Biochemistry, University of Alabama, Tuscaloosa, Alabama 35487, USA
| | - Johnny B Herbert
- Department of Chemistry and Biochemistry, University of Alabama, Tuscaloosa, Alabama 35487, USA
| | - Danielle A McGaha
- Department of Chemistry and Biochemistry, University of Alabama, Tuscaloosa, Alabama 35487, USA
| | - Vy Nguyen
- Department of Chemistry and Biochemistry, Loyola University New Orleans, New Orleans, Louisiana 70118, USA
| | - Allyn J Schoeffler
- Department of Chemistry and Biochemistry, Loyola University New Orleans, New Orleans, Louisiana 70118, USA
| | - Jack A Dunkle
- Department of Chemistry and Biochemistry, University of Alabama, Tuscaloosa, Alabama 35487, USA
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18
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Role of Efflux Pump-Mediated Antibiotic Resistance in Quorum Sensing-Regulated Biofilm Formation by Salmonella Typhimurium. Pathogens 2022; 11:pathogens11020147. [PMID: 35215091 PMCID: PMC8877114 DOI: 10.3390/pathogens11020147] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Revised: 01/20/2022] [Accepted: 01/24/2022] [Indexed: 02/06/2023] Open
Abstract
This study was designed to assess the influence of efflux pump activity on the biofilm formation in Salmonella Typhimurium. Salmonella enterica subsp. enterica serovar Typhimurium ATCC 19585 (STWT) and clinically isolated S. Typhimurium CCARM 8009 (STCI) were treated with ceftriaxone (CEF), chloramphenicol (CHL), ciprofloxacin (CIP), erythromycin (ERY), norfloxacin (NOR), and tetracycline (TET) in autoinducer-containing media in the absence and presence of phenylalanine-arginine β-naphthylamide (PAβN) to compare efflux pump activity with biofilm-forming ability. The susceptibilities of STWT and STCI were increased in the presence of PAβN. ERY+PAβN showed the highest decrease in the minimum inhibitory concentration (MIC) of ERY from 256 to 2 μg/mL against STWT and STCI. The antimicrobial activity of NOR against planktonic cells was significantly increased in the presence of PAβN, showing the lowest numbers of STWT (3.2 log CFU/cm2), and the TET+PAβN effectively inhibited the growth of STCI (5.2 log CFU/cm2). The lowest biofilm-forming abilities were observed at NOR+PAβN against STWT (biofilm-forming index, BFI < 0.41) and CEF+PAβN against STCI (BFI = 0.32). The bacteria swimming motility and relative fitness varied depending on the antibiotic and PAβN treatments. The motility diameters of STWT were significantly decreased by NOR+PAβN (6 mm) and TET+PAβN (15 mm), while the lowest motility of STCI was observed at CIP+PAβN (8 mm). The significant decrease in the relative fitness levels of STWT and STCI was observed at CIP+PAβN and NOR+PAβN. The PAβN as an efflux pump inhibitor (EPI) can improve the antimicrobial and anti-biofilm efficacy of antibiotics against S. Typhimurium. This study provides useful information for understanding the role of efflux pump activity in quorum sensing-regulated biofilm formation and also emphasizes the necessity of the discovery of novel EPIs for controlling biofilm formation by antibiotic-resistant pathogens.
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19
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Ren Z, Wang S, Liu D, Yu J, Zhang X, Zhao P, Sun Y, Han S. Control strategies for the vertical gene transfer of quinolone ARGs in Escherichia coli through molecular modification and molecular dynamics. JOURNAL OF HAZARDOUS MATERIALS 2021; 420:126667. [PMID: 34329116 DOI: 10.1016/j.jhazmat.2021.126667] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Revised: 07/05/2021] [Accepted: 07/14/2021] [Indexed: 06/13/2023]
Abstract
This study investigates the regulation of the vertical gene transfer of quinolones' antibiotic resistance genes (ARGs) through a combination of source modification and process control. In source prevention, 29 Escherichia coli (E. coli) DNA gyrase subunit A mutant proteins were constructed, the B-G mutant protein displayed the greatest reduction in binding effect (-25.98%). Based on this, a 3D-QSAR model was constructed, and LEV-2 and LEV-9 QNs derivatives were designed based on Levofloxacin (LEV), and their binding effect with B-G mutant protein was found be increased by 13.24% and 19.40%. The drug resistance mechanism of E. coli was explored based on molecular docking technology and protein hydrophobic interaction theory. Most of the amino acid resistance mutations changed from hydrophilic to lipophilic, which inhibited the binding of QNs to mutant protein A subunit, and further reduced the bactericidal effect of QNs. In process control, Huoxiang-Zhengqi, stroke-physiological saline solution (SPSS), and Lycium barbarum (L. barbarum) was found to be 164.82% higher than that of the blank control group. The purpose of this study is to provide a theoretical support for the joint regulation of QNs' ARGs in organisms and the research and development on green alternatives to QNs compounds.
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Affiliation(s)
- Zhixing Ren
- College of Forestry, Northeast Forestry University, No. 26 Hexing Road, Harbin 150040, China.
| | - Shen Wang
- College of Forestry, Northeast Forestry University, No. 26 Hexing Road, Harbin 150040, China.
| | - Dong Liu
- College of Forestry, Northeast Forestry University, No. 26 Hexing Road, Harbin 150040, China.
| | - Jie Yu
- College of Forestry, Northeast Forestry University, No. 26 Hexing Road, Harbin 150040, China.
| | - Xiaoyuan Zhang
- College of Forestry, Northeast Forestry University, No. 26 Hexing Road, Harbin 150040, China.
| | - Pingnan Zhao
- College of Forestry, Northeast Forestry University, No. 26 Hexing Road, Harbin 150040, China.
| | - Yuxuan Sun
- College of Forestry, Northeast Forestry University, No. 26 Hexing Road, Harbin 150040, China.
| | - Song Han
- College of Forestry, Northeast Forestry University, No. 26 Hexing Road, Harbin 150040, China.
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20
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Cryo-EM Determination of Eravacycline-Bound Structures of the Ribosome and the Multidrug Efflux Pump AdeJ of Acinetobacter baumannii. mBio 2021; 12:e0103121. [PMID: 34044590 PMCID: PMC8263017 DOI: 10.1128/mbio.01031-21] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Antibiotic-resistant strains of the Gram-negative pathogen Acinetobacter baumannii have emerged as a significant global health threat. One successful therapeutic option to treat bacterial infections has been to target the bacterial ribosome. However, in many cases, multidrug efflux pumps within the bacterium recognize and extrude these clinically important antibiotics designed to inhibit the protein synthesis function of the bacterial ribosome. Thus, multidrug efflux within A. baumannii and other highly drug-resistant strains is a major cause of failure of drug-based treatments of infectious diseases. We here report the first structures of the Acinetobacterdrug efflux (Ade)J pump in the presence of the antibiotic eravacycline, using single-particle cryo-electron microscopy (cryo-EM). We also describe cryo-EM structures of the eravacycline-bound forms of the A. baumannii ribosome, including the 70S, 50S, and 30S forms. Our data indicate that the AdeJ pump primarily uses hydrophobic interactions to bind eravacycline, while the 70S ribosome utilizes electrostatic interactions to bind this drug. Our work here highlights how an antibiotic can bind multiple bacterial targets through different mechanisms and potentially enables drug optimization by taking advantage of these different modes of ligand binding.
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21
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Klenotic PA, Moseng MA, Morgan CE, Yu EW. Structural and Functional Diversity of Resistance-Nodulation-Cell Division Transporters. Chem Rev 2021; 121:5378-5416. [PMID: 33211490 PMCID: PMC8119314 DOI: 10.1021/acs.chemrev.0c00621] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Multidrug resistant (MDR) bacteria are a global threat with many common infections becoming increasingly difficult to eliminate. While significant effort has gone into the development of potent biocides, the effectiveness of many first-line antibiotics has been diminished due to adaptive resistance mechanisms. Bacterial membrane proteins belonging to the resistance-nodulation-cell division (RND) superfamily play significant roles in mediating bacterial resistance to antimicrobials. They participate in multidrug efflux and cell wall biogenesis to transform bacterial pathogens into "superbugs" that are resistant even to last resort antibiotics. In this review, we summarize the RND superfamily of efflux transporters with a primary focus on the assembly and function of the inner membrane pumps. These pumps are critical for extrusion of antibiotics from the cell as well as the transport of lipid moieties to the outer membrane to establish membrane rigidity and stability. We analyze recently solved structures of bacterial inner membrane efflux pumps as to how they bind and transport their substrates. Our cumulative data indicate that these RND membrane proteins are able to utilize different oligomerization states to achieve particular activities, including forming MDR pumps and cell wall remodeling machineries, to ensure bacterial survival. This mechanistic insight, combined with simulated docking techniques, allows for the design and optimization of new efflux pump inhibitors to more effectively treat infections that today are difficult or impossible to cure.
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Affiliation(s)
- Philip A. Klenotic
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland OH 44106, USA
| | - Mitchell A. Moseng
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland OH 44106, USA
| | - Christopher E. Morgan
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland OH 44106, USA
| | - Edward W. Yu
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland OH 44106, USA
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22
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Alav I, Kobylka J, Kuth MS, Pos KM, Picard M, Blair JMA, Bavro VN. Structure, Assembly, and Function of Tripartite Efflux and Type 1 Secretion Systems in Gram-Negative Bacteria. Chem Rev 2021; 121:5479-5596. [PMID: 33909410 PMCID: PMC8277102 DOI: 10.1021/acs.chemrev.1c00055] [Citation(s) in RCA: 96] [Impact Index Per Article: 32.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Indexed: 12/11/2022]
Abstract
Tripartite efflux pumps and the related type 1 secretion systems (T1SSs) in Gram-negative organisms are diverse in function, energization, and structural organization. They form continuous conduits spanning both the inner and the outer membrane and are composed of three principal components-the energized inner membrane transporters (belonging to ABC, RND, and MFS families), the outer membrane factor channel-like proteins, and linking the two, the periplasmic adaptor proteins (PAPs), also known as the membrane fusion proteins (MFPs). In this review we summarize the recent advances in understanding of structural biology, function, and regulation of these systems, highlighting the previously undescribed role of PAPs in providing a common architectural scaffold across diverse families of transporters. Despite being built from a limited number of basic structural domains, these complexes present a staggering variety of architectures. While key insights have been derived from the RND transporter systems, a closer inspection of the operation and structural organization of different tripartite systems reveals unexpected analogies between them, including those formed around MFS- and ATP-driven transporters, suggesting that they operate around basic common principles. Based on that we are proposing a new integrated model of PAP-mediated communication within the conformational cycling of tripartite systems, which could be expanded to other types of assemblies.
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Affiliation(s)
- Ilyas Alav
- Institute
of Microbiology and Infection, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom
| | - Jessica Kobylka
- Institute
of Biochemistry, Biocenter, Goethe Universität
Frankfurt, Max-von-Laue-Straße 9, D-60438 Frankfurt, Germany
| | - Miriam S. Kuth
- Institute
of Biochemistry, Biocenter, Goethe Universität
Frankfurt, Max-von-Laue-Straße 9, D-60438 Frankfurt, Germany
| | - Klaas M. Pos
- Institute
of Biochemistry, Biocenter, Goethe Universität
Frankfurt, Max-von-Laue-Straße 9, D-60438 Frankfurt, Germany
| | - Martin Picard
- Laboratoire
de Biologie Physico-Chimique des Protéines Membranaires, CNRS
UMR 7099, Université de Paris, 75005 Paris, France
- Fondation
Edmond de Rothschild pour le développement de la recherche
Scientifique, Institut de Biologie Physico-Chimique, 75005 Paris, France
| | - Jessica M. A. Blair
- Institute
of Microbiology and Infection, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom
| | - Vassiliy N. Bavro
- School
of Life Sciences, University of Essex, Colchester, CO4 3SQ United Kingdom
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23
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Structural Insights into Transporter-Mediated Drug Resistance in Infectious Diseases. J Mol Biol 2021; 433:167005. [PMID: 33891902 DOI: 10.1016/j.jmb.2021.167005] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Revised: 04/12/2021] [Accepted: 04/12/2021] [Indexed: 02/07/2023]
Abstract
Infectious diseases present a major threat to public health globally. Pathogens can acquire resistance to anti-infectious agents via several means including transporter-mediated efflux. Typically, multidrug transporters feature spacious, dynamic, and chemically malleable binding sites to aid in the recognition and transport of chemically diverse substrates across cell membranes. Here, we discuss recent structural investigations of multidrug transporters involved in resistance to infectious diseases that belong to the ATP-binding cassette (ABC) superfamily, the major facilitator superfamily (MFS), the drug/metabolite transporter (DMT) superfamily, the multidrug and toxic compound extrusion (MATE) family, the small multidrug resistance (SMR) family, and the resistance-nodulation-division (RND) superfamily. These structural insights provide invaluable information for understanding and combatting multidrug resistance.
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24
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Emergence of two AcrB substitutions conferring multidrug resistance to Salmonella spp. Antimicrob Agents Chemother 2021; 65:AAC.01589-20. [PMID: 33685897 PMCID: PMC8092907 DOI: 10.1128/aac.01589-20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
AcrAB-TolC is a major tripartite multidrug efflux pump conferring resistance to a wide variety of compounds in Gram-negative pathogens. Many AcrB mutants have been constructed through site-directed mutagenesis to probe the mechanism of AcrB function in antibiotic resistance. However, much less is known about the actual drug resistance related mutants that naturally occur in clinically isolated pathogens. Here, we report two novel AcrB substitutions, M78I and P319L, in clinically isolated Salmonella strains with high-level ciprofloxacin resistance. Plasmids expressing the detected acrB mutations were constructed and introduced into SL1344△acrB Antimicrobial susceptibility assay showed that all AcrB M78I, AcrB P319L and AcrB M78I/319L conferred reduced susceptibilities to multiple substrates, including fluoroquinolones, erythromycin, tetracyclines, bile salts and dyes. Site-directed mutagenesis and MIC results revealed that increased hydrophobicity of M78I was one of the reasons why AcrB M78I had lower susceptibility to fluoroquinolones. Fluorescence labeling experiments suggested that the AcrB M78I substitution enhanced the binding of substrates to certain amino acid sites in the efflux pathway (e.g., site Q89, E673 and F617) and weakened the binding to other amino acids (e.g., S134 and N274). Structural modeling disclosed the increased flexibility of Leu was favorable for the functional rotation of AcrB compared to the original Pro. AcrA 319L makes the functional rotation of AcrB more flexible, this enables substrate efflux more efficiently. In order to understand the mechanism of AcrAB-TolC drug efflux well, interaction between AcrA and AcrB in the role of substrate efflux of AcrAB-TolC should be further investigated.
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Ahmed MS, Lauersen KJ, Ikram S, Li C. Efflux Transporters' Engineering and Their Application in Microbial Production of Heterologous Metabolites. ACS Synth Biol 2021; 10:646-669. [PMID: 33751883 DOI: 10.1021/acssynbio.0c00507] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Metabolic engineering of microbial hosts for the production of heterologous metabolites and biochemicals is an enabling technology to generate meaningful quantities of desired products that may be otherwise difficult to produce by traditional means. Heterologous metabolite production can be restricted by the accumulation of toxic products within the cell. Efflux transport proteins (transporters) provide a potential solution to facilitate the export of these products, mitigate toxic effects, and enhance production. Recent investigations using knockout lines, heterologous expression, and expression profiling of transporters have revealed candidates that can enhance the export of heterologous metabolites from microbial cell systems. Transporter engineering efforts have revealed that some exhibit flexible substrate specificity and may have broader application potentials. In this Review, the major superfamilies of efflux transporters, their mechanistic modes of action, selection of appropriate efflux transporters for desired compounds, and potential transporter engineering strategies are described for potential applications in enhancing engineered microbial metabolite production. Future studies in substrate recognition, heterologous expression, and combinatorial engineering of efflux transporters will assist efforts to enhance heterologous metabolite production in microbial hosts.
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Affiliation(s)
- Muhammad Saad Ahmed
- Institute for Synthetic Biosystem/Department of Biochemical Engineering, School of Chemistry and Chemical Engineering, Beijing Institute of Technology (BIT), Beijing 100081, P. R. China
- Department of Biological Sciences, National University of Medical Sciences (NUMS), Abid Majeed Road, The Mall, Rawalpindi 46000, Pakistan
| | - Kyle J. Lauersen
- Biological and Environmental Sciences and Engineering Division (BESE), King Abdullah University of Science and Technology (KAUST), Thuwal 23955, Kingdom of Saudi Arabia
| | - Sana Ikram
- Beijing Higher Institution Engineering Research Center for Food Additives and Ingredients, Beijing Technology & Business University (BTBU), Beijing 100048, P. R. China
| | - Chun Li
- Institute for Synthetic Biosystem/Department of Biochemical Engineering, School of Chemistry and Chemical Engineering, Beijing Institute of Technology (BIT), Beijing 100081, P. R. China
- SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering, Key Laboratory of Systems Bioengineering, Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300350, P. R. China
- Key Laboratory for Industrial Biocatalysis, Ministry of Education, Department of Chemical Engineering, Tsinghua University, Beijing 100084, P. R. China
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Abstract
Gram-negative bacteria utilize the resistance-nodulation-cell division (RND) superfamily of efflux pumps to expel a variety of toxic compounds from the cell. The Escherichia coli CusA membrane protein, which recognizes and extrudes biocidal Cu(I) and Ag(I) ions, belongs to the heavy-metal efflux (HME) subfamily of RND efflux pumps. We here report four structures of the trimeric CusA heavy-metal efflux pump in the presence of Cu(I) using single-particle cryo-electron microscopy (cryo-EM). We discover that different CusA protomers within the trimer are able to bind Cu(I) ions simultaneously. Our structural data combined with molecular dynamics (MD) simulations allow us to propose a mechanism for ion transport where each CusA protomer functions independently within the trimer.IMPORTANCE The bacterial RND superfamily of efflux pumps mediate resistance to a variety of biocides, including Cu(I) and Ag(I) ions. Here we report four cryo-EM structures of the trimeric CusA pump in the presence of Cu(I). Combined with MD simulations, our data indicate that each CusA protomer within the trimer recognizes and extrudes Cu(I) independently.
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Morgan CE, Glaza P, Leus IV, Trinh A, Su CC, Cui M, Zgurskaya HI, Yu EW. Cryoelectron Microscopy Structures of AdeB Illuminate Mechanisms of Simultaneous Binding and Exporting of Substrates. mBio 2021; 12:e03690-20. [PMID: 33622726 PMCID: PMC8545137 DOI: 10.1128/mbio.03690-20] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Accepted: 01/11/2021] [Indexed: 12/31/2022] Open
Abstract
Acinetobacter baumannii is a Gram-negative pathogen that has emerged as one of the most highly antibiotic-resistant bacteria worldwide. Multidrug efflux within these highly drug-resistant strains and other opportunistic pathogens is a major cause of failure of drug-based treatments of infectious diseases. The best-characterized multidrug efflux system in A. baumannii is the prevalent Acinetobacterdrug efflux B (AdeB) pump, which is a member of the resistance-nodulation-cell division (RND) superfamily. Here, we report six structures of the trimeric AdeB multidrug efflux pump in the presence of ethidium bromide using single-particle cryoelectron microscopy (cryo-EM). These structures allow us to directly observe various novel conformational states of the AdeB trimer, including the transmembrane region of trimeric AdeB can be associated with form a trimer assembly or dissociated into "dimer plus monomer" and "monomer plus monomer plus monomer" configurations. We also discover that a single AdeB protomer can simultaneously anchor a number of ethidium ligands and that different AdeB protomers can bind ethidium molecules simultaneously. Combined with molecular dynamics (MD) simulations, we reveal a drug transport mechanism that involves multiple multidrug-binding sites and various transient states of the AdeB membrane protein. Our data suggest that each AdeB protomer within the trimer binds and exports drugs independently.IMPORTANCEAcinetobacter baumannii has emerged as one of the most highly antibiotic-resistant Gram-negative pathogens. The prevalent AdeB multidrug efflux pump mediates resistance to a broad spectrum of clinically relevant antimicrobial agents. Here, we report six cryo-EM structures of the trimeric AdeB pump in the presence of ethidium bromide. We discover that a single AdeB protomer can simultaneously anchor a number of ligands, and different AdeB protomers can bind ethidium molecules simultaneously. The results indicate that each AdeB protomer within the trimer recognizes and extrudes drugs independently.
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Affiliation(s)
- Christopher E Morgan
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
| | - Przemyslaw Glaza
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
| | - Inga V Leus
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma, USA
| | - Anhthu Trinh
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma, USA
| | - Chih-Chia Su
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
| | - Meng Cui
- Department of Pharmaceutical Sciences, Northeastern University School of Pharmacy, Boston, Massachusetts, USA
| | - Helen I Zgurskaya
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma, USA
| | - Edward W Yu
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
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An Analysis of the Novel Fluorocycline TP-6076 Bound to Both the Ribosome and Multidrug Efflux Pump AdeJ from Acinetobacter baumannii. mBio 2021; 13:e0373221. [PMID: 35100868 PMCID: PMC8805024 DOI: 10.1128/mbio.03732-21] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Antibiotic resistance among bacterial pathogens continues to pose a serious global health threat. Multidrug-resistant (MDR) strains of the Gram-negative organism Acinetobacter baumannii utilize a number of resistance determinants to evade current antibiotics. One of the major resistance mechanisms employed by these pathogens is the use of multidrug efflux pumps. These pumps extrude xenobiotics directly out of bacterial cells, resulting in treatment failures when common antibiotics are administered. Here, the structure of the novel tetracycline antibiotic TP-6076, bound to both the Acinetobacter drug efflux pump AdeJ and the ribosome from Acinetobacter baumannii, using single-particle cryo-electron microscopy (cryo-EM), is elucidated. In this work, the structure of the AdeJ-TP-6076 complex is solved, and we show that AdeJ utilizes a network of hydrophobic interactions to recognize this fluorocycline. Concomitant with this, we elucidate three structures of TP-6076 bound to the A. baumannii ribosome and determine that its binding is stabilized largely by electrostatic interactions. We then compare the differences in binding modes between TP-6076 and the related tetracycline antibiotic eravacycline in both targets. These differences suggest that modifications to the tetracycline core may be able to alter AdeJ binding while maintaining interactions with the ribosome. Together, this work highlights how different mechanisms are used to stabilize the binding of tetracycline-based compounds to unique bacterial targets and provides guidance for the future clinical development of tetracycline antibiotics. IMPORTANCE Treatment of antibiotic-resistant organisms such as A. baumannii represents an ongoing issue for modern medicine. The multidrug efflux pump AdeJ serves as a major resistance determinant in A. baumannii through its action of extruding antibiotics from the cell. In this work, we use cryo-EM to show how AdeJ recognizes the experimental tetracycline antibiotic TP-6076 and prevents this drug from interacting with the A. baumannii ribosome. Since AdeJ and the ribosome use different binding modes to stabilize interactions with TP-6076, exploiting these differences may guide future drug development for combating antibiotic-resistant A. baumannii and potentially other strains of MDR bacteria.
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Sahu R, Mohapatra RK, Al-Resayes SI, Das D, Parhi PK, Rahman S, Pintilie L, Kumar M, Azam M, Ansari A. An efficient synthesis towards the core of Crinipellin: TD-DFT and docking studies. JOURNAL OF SAUDI CHEMICAL SOCIETY 2021. [DOI: 10.1016/j.jscs.2020.101193] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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A small molecule that mitigates bacterial infection disrupts Gram-negative cell membranes and is inhibited by cholesterol and neutral lipids. PLoS Pathog 2020; 16:e1009119. [PMID: 33290418 PMCID: PMC7748285 DOI: 10.1371/journal.ppat.1009119] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2020] [Revised: 12/18/2020] [Accepted: 11/01/2020] [Indexed: 01/01/2023] Open
Abstract
Infections caused by Gram-negative bacteria are difficult to fight because these pathogens exclude or expel many clinical antibiotics and host defense molecules. However, mammals have evolved a substantial immune arsenal that weakens pathogen defenses, suggesting the feasibility of developing therapies that work in concert with innate immunity to kill Gram-negative bacteria. Using chemical genetics, we recently identified a small molecule, JD1, that kills Salmonella enterica serovar Typhimurium (S. Typhimurium) residing within macrophages. JD1 is not antibacterial in standard microbiological media, but rapidly inhibits growth and curtails bacterial survival under broth conditions that compromise the outer membrane or reduce efflux pump activity. Using a combination of cellular indicators and super resolution microscopy, we found that JD1 damaged bacterial cytoplasmic membranes by increasing fluidity, disrupting barrier function, and causing the formation of membrane distortions. We quantified macrophage cell membrane integrity and mitochondrial membrane potential and found that disruption of eukaryotic cell membranes required approximately 30-fold more JD1 than was needed to kill bacteria in macrophages. Moreover, JD1 preferentially damaged liposomes with compositions similar to E. coli inner membranes versus mammalian cell membranes. Cholesterol, a component of mammalian cell membranes, was protective in the presence of neutral lipids. In mice, intraperitoneal administration of JD1 reduced tissue colonization by S. Typhimurium. These observations indicate that during infection, JD1 gains access to and disrupts the cytoplasmic membrane of Gram-negative bacteria, and that neutral lipids and cholesterol protect mammalian membranes from JD1-mediated damage. Thus, it may be possible to develop therapeutics that exploit host innate immunity to gain access to Gram-negative bacteria and then preferentially damage the bacterial cell membrane over host membranes.
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Perturbed structural dynamics underlie inhibition and altered efflux of the multidrug resistance pump AcrB. Nat Commun 2020; 11:5565. [PMID: 33149158 PMCID: PMC7642415 DOI: 10.1038/s41467-020-19397-2] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Accepted: 10/08/2020] [Indexed: 01/22/2023] Open
Abstract
Resistance–nodulation–division efflux pumps play a key role in inherent and evolved multidrug resistance in bacteria. AcrB, a prototypical member of this protein family, extrudes a wide range of antimicrobial agents out of bacteria. Although high-resolution structures exist for AcrB, its conformational fluctuations and their putative role in function are largely unknown. Here, we determine these structural dynamics in the presence of substrates using hydrogen/deuterium exchange mass spectrometry, complemented by molecular dynamics simulations, and bacterial susceptibility studies. We show that an efflux pump inhibitor potentiates antibiotic activity by restraining drug-binding pocket dynamics, rather than preventing antibiotic binding. We also reveal that a drug-binding pocket substitution discovered within a multidrug resistant clinical isolate modifies the plasticity of the transport pathway, which could explain its altered substrate efflux. Our results provide insight into the molecular mechanism of drug export and inhibition of a major multidrug efflux pump and the directive role of its dynamics. AcrB is a prototypical resistance–nodulation–division (RND) bacterial transporter, conferring resistance to a variety of antibiotics. HDX-MS and other, complementary approaches offer insight into AcrB structural dynamics and suggest the molecular mechanisms underlying drug export and inhibition of this multidrug-resistance conferring pump.
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Rathi E, Kumar A, Kini SG. Computational approaches in efflux pump inhibitors: current status and prospects. Drug Discov Today 2020; 25:1883-1890. [PMID: 32712312 DOI: 10.1016/j.drudis.2020.07.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Revised: 07/02/2020] [Accepted: 07/13/2020] [Indexed: 01/02/2023]
Abstract
Treatment of bacterial infections is currently threatened by the development of antibiotic resistance and a poor pipeline of new antibiotics. Efflux pumps (EPs) are an integral part of the defense machinery of bacteria, preventing the entry of molecules, such as antibiotics, into the intracellular environment and resulting in antibiotic resistance. Therefore, research has focused on the discovery of novel EP inhibitors (EPIs), such as PAβN, D13-9001, and MBX2319. however, there are still no US Food and Drug Administration (FDA)-approved drugs targeting EPs because of the inadequate assimilation of the inhibitors. Here, we discuss the use of computational approaches for molecular mechanistic studies of EPIs to help direct future research.
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Affiliation(s)
- Ekta Rathi
- Department of Pharmaceutical Chemistry, Manipal College of Pharmaceutical Sciences, Manipal Academy of Higher Education, Manipal, 576104, India
| | - Avinash Kumar
- Department of Pharmaceutical Chemistry, Manipal College of Pharmaceutical Sciences, Manipal Academy of Higher Education, Manipal, 576104, India
| | - Suvarna G Kini
- Department of Pharmaceutical Chemistry, Manipal College of Pharmaceutical Sciences, Manipal Academy of Higher Education, Manipal, 576104, India.
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Cryo-EM Structures of a Gonococcal Multidrug Efflux Pump Illuminate a Mechanism of Drug Recognition and Resistance. mBio 2020; 11:mBio.00996-20. [PMID: 32457251 PMCID: PMC7251214 DOI: 10.1128/mbio.00996-20] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Neisseria gonorrhoeae has become a highly antimicrobial-resistant Gram-negative pathogen. Multidrug efflux is a major mechanism that N. gonorrhoeae uses to counteract the action of multiple classes of antibiotics. It appears that gonococci bearing mosaic-like sequences within the gene mtrD, encoding the most predominant and clinically important transporter of any gonococcal multidrug efflux pump, significantly elevate drug resistance and enhance transport function. Here, we report cryo-electron microscopy (EM) structures of N. gonorrhoeae MtrD carrying a mosaic-like sequence that allow us to understand the mechanism of drug recognition. Our work will ultimately inform structure-guided drug design for inhibiting these critical multidrug efflux pumps. Neisseria gonorrhoeae is an obligate human pathogen and causative agent of the sexually transmitted infection (STI) gonorrhea. The most predominant and clinically important multidrug efflux system in N. gonorrhoeae is the multiple transferrable resistance (Mtr) pump, which mediates resistance to a number of different classes of structurally diverse antimicrobial agents, including clinically used antibiotics (e.g., β-lactams and macrolides), dyes, detergents and host-derived antimicrobials (e.g., cationic antimicrobial peptides and bile salts). Recently, it has been found that gonococci bearing mosaic-like sequences within the mtrD gene can result in amino acid changes that increase the MtrD multidrug efflux pump activity, probably by influencing antimicrobial recognition and/or extrusion to elevate the level of antibiotic resistance. Here, we report drug-bound solution structures of the MtrD multidrug efflux pump carrying a mosaic-like sequence using single-particle cryo-electron microscopy, with the antibiotics bound deeply inside the periplasmic domain of the pump. Through this structural approach coupled with genetic studies, we identify critical amino acids that are important for drug resistance and propose a mechanism for proton translocation.
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Koukos P, Bonvin A. Integrative Modelling of Biomolecular Complexes. J Mol Biol 2020; 432:2861-2881. [DOI: 10.1016/j.jmb.2019.11.009] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2019] [Revised: 11/12/2019] [Accepted: 11/13/2019] [Indexed: 12/31/2022]
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Atzori A, Malloci G, Cardamone F, Bosin A, Vargiu AV, Ruggerone P. Molecular Interactions of Carbapenem Antibiotics with the Multidrug Efflux Transporter AcrB of Escherichia coli. Int J Mol Sci 2020; 21:E860. [PMID: 32013182 PMCID: PMC7037162 DOI: 10.3390/ijms21030860] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Accepted: 01/26/2020] [Indexed: 12/22/2022] Open
Abstract
The drug/proton antiporter AcrB, engine of the major efflux pump AcrAB(Z)-TolC of Escherichia coli and other bacteria, is characterized by its impressive ability to transport chemically diverse compounds, conferring a multi-drug resistance (MDR) phenotype. Although hundreds of small molecules are known to be AcrB substrates, only a few co-crystal structures are available to date. Computational methods have been therefore intensively employed to provide structural and dynamical fingerprints related to transport and inhibition of AcrB. In this work, we performed a systematic computational investigation to study the interaction between representative carbapenem antibiotics and AcrB. We focused on the interaction of carbapenems with the so-called distal pocket, a region known for its importance in binding inhibitors and substrates of AcrB. Our findings reveal how the different physico-chemical nature of these antibiotics is reflected on their binding preference for AcrB. The molecular-level information provided here could help design new antibiotics less susceptible to the efflux mechanism.
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Affiliation(s)
| | - Giuliano Malloci
- Department of Physics, University of Cagliari, 09042 Monserrato (CA), Italy; (A.A.); (F.C.); (A.B.); (P.R.)
| | | | | | - Attilio Vittorio Vargiu
- Department of Physics, University of Cagliari, 09042 Monserrato (CA), Italy; (A.A.); (F.C.); (A.B.); (P.R.)
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Hooda Y, Sajib MSI, Rahman H, Luby SP, Bondy-Denomy J, Santosham M, Andrews JR, Saha SK, Saha S. Molecular mechanism of azithromycin resistance among typhoidal Salmonella strains in Bangladesh identified through passive pediatric surveillance. PLoS Negl Trop Dis 2019; 13:e0007868. [PMID: 31730615 PMCID: PMC6881056 DOI: 10.1371/journal.pntd.0007868] [Citation(s) in RCA: 74] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Revised: 11/27/2019] [Accepted: 10/24/2019] [Indexed: 12/11/2022] Open
Abstract
Background With the rise in fluoroquinolone-resistant Salmonella Typhi and the recent emergence of ceftriaxone resistance, azithromycin is one of the last oral drugs available against typhoid for which resistance is uncommon. Its increasing use, specifically in light of the ongoing outbreak of extensively drug-resistant (XDR) Salmonella Typhi (resistant to chloramphenicol, ampicillin, cotrimoxazole, streptomycin, fluoroquinolones and third-generation cephalosporins) in Pakistan, places selective pressure for the emergence and spread of azithromycin-resistant isolates. However, little is known about azithromycin resistance in Salmonella, and no molecular data are available on its mechanism. Methods and findings We conducted typhoid surveillance in the two largest pediatric hospitals of Bangladesh from 2009–2016. All typhoidal Salmonella strains were screened for azithromycin resistance using disc diffusion and resistance was confirmed using E-tests. In total, we identified 1,082 Salmonella Typhi and Paratyphi A strains; among these, 13 strains (12 Typhi, 1 Paratyphi A) were azithromycin-resistant (MIC range: 32–64 μg/ml) with the first case observed in 2013. We sequenced the resistant strains, but no molecular basis of macrolide resistance was identified by the currently available antimicrobial resistance prediction tools. A whole genome SNP tree, made using RAxML, showed that the 12 Typhi resistant strains clustered together within the 4.3.1.1 sub-clade (H58 lineage 1). We found a non-synonymous single-point mutation exclusively in these 12 strains in the gene encoding AcrB, an efflux pump that removes small molecules from bacterial cells. The mutation changed the conserved amino acid arginine (R) at position 717 to a glutamine (Q). To test the role of R717Q present in azithromycin-resistant strains, we cloned acrB from azithromycin-resistant and sensitive strains, expressed them in E. coli, Typhi and Paratyphi A strains and tested their azithromycin susceptibility. Expression of AcrB-R717Q in E. coli and Typhi strains increased the minimum inhibitory concentration (MIC) for azithromycin by 11- and 3-fold respectively. The azithromycin-resistant Paratyphi A strain also contained a mutation at R717 (R717L), whose introduction in E. coli and Paratyphi A strains increased MIC by 7- and 3-fold respectively, confirming the role of R717 mutations in conferring azithromycin resistance. Conclusions This report confirms 12 azithromycin-resistant Salmonella Typhi strains and one Paratyphi A strain. The molecular basis of this resistance is one mutation in the AcrB protein at position 717. This is the first report demonstrating the impact of this non-synonymous mutation in conferring macrolide resistance in a clinical setting. With increasing azithromycin use, strains with R717 mutations may spread and be acquired by XDR strains. An azithromycin-resistant XDR strain would shift enteric fever treatment from outpatient departments, where patients are currently treated with oral azithromycin, to inpatient departments to be treated with injectable antibiotics like carbapenems, thereby further burdening already struggling health systems in endemic regions. Moreover, with the dearth of novel antimicrobials in the horizon, we risk losing our primary defense against widespread mortality from typhoid. In addition to rolling out the WHO prequalified typhoid conjugate vaccine in endemic areas to decrease the risk of pan-resistant Salmonella Typhi strains, it is also imperative to implement antimicrobial stewardship and water sanitation and hygiene intervention to decrease the overall burden of enteric fever. With the outbreak of extensively resistant (XDR) typhoid fever in Pakistan, azithromycin has become the last oral drug to treat typhoid. Although no azithromycin resistant XDR isolate has been reported to date, the increasing use of azithromycin and the clear historical record of widespread dissemination of resistance to all previously widely used antimicrobials by typhoidal Salmonella, suggest we will soon face strains resistant to all oral antibiotics. This makes it imperative to elucidate the mechanism of azithromycin resistance in typhoidal Salmonella. We tested 1,082 typhoidal Salmonella isolates from the two largest pediatric hospitals of Bangladesh and identified 13 azithromycin-resistant isolates. Using comparative genomics, we identified a mutation in a specific protein called AcrB that makes these isolates resistant to azithromycin. All azithromycin-resistant strains were susceptible to cephalosporin but resistant to all other oral antibiotics. The Pakistan outbreak strain is resistant to all common oral antibiotics and only susceptible to azithromycin. Acquisition of the plasmid that confers cephalosporin resistance in XDR strains by the Bangladeshi azithromycin-resistant strains or rise of the AcrB mutation in the XDR strains could be the end of oral treatment for typhoid. This poses serious threats to the health system of LMICs where typhoid is endemic. Currently, the majority of typhoid patients are prescribed oral treatment in the outpatient department, but an azithromycin-resistant XDR strain would shift enteric fever treatment from outpatient departments to inpatient departments to be treated with injectable antibiotics like carbapenems, further burdening already struggling health systems in endemic regions. Moreover, with the dearth of novel antimicrobials in the horizon, we risk losing our primary defense against widespread mortality from enteric fever.
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Affiliation(s)
- Yogesh Hooda
- Child Health Research Foundation, Department of Microbiology, Dhaka Shishu Hospital, Dhaka, Bangladesh
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Mohammad S. I. Sajib
- Child Health Research Foundation, Department of Microbiology, Dhaka Shishu Hospital, Dhaka, Bangladesh
| | - Hafizur Rahman
- Child Health Research Foundation, Department of Microbiology, Dhaka Shishu Hospital, Dhaka, Bangladesh
| | - Stephen P. Luby
- Division of Infectious Diseases and Geographic Medicine, Stanford University School of Medicine, Stanford, California, United States of America
| | - Joseph Bondy-Denomy
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, California, United States of America
- Quantitative Biosciences Institute, University of California, San Francisco, San Francisco, California, United States of America
| | - Mathuram Santosham
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America
| | - Jason R. Andrews
- Division of Infectious Diseases and Geographic Medicine, Stanford University School of Medicine, Stanford, California, United States of America
| | - Samir K. Saha
- Child Health Research Foundation, Department of Microbiology, Dhaka Shishu Hospital, Dhaka, Bangladesh
- Bangladesh Institute of Child Health, Dhaka Shishu Hospital, Dhaka, Bangladesh
- * E-mail: (SKS); (SS)
| | - Senjuti Saha
- Child Health Research Foundation, Department of Microbiology, Dhaka Shishu Hospital, Dhaka, Bangladesh
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America
- * E-mail: (SKS); (SS)
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Cheng YH, Lin TL, Lin YT, Wang JT. A putative RND-type efflux pump, H239_3064, contributes to colistin resistance through CrrB in Klebsiella pneumoniae. J Antimicrob Chemother 2019; 73:1509-1516. [PMID: 29506266 PMCID: PMC5961088 DOI: 10.1093/jac/dky054] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Accepted: 01/27/2018] [Indexed: 12/20/2022] Open
Abstract
Background Colistin is one of the last-resort antibiotics used to treat carbapenem-resistant Klebsiella pneumoniae infection. Our previous studies indicated that clinical strains encoding CrrB with amino acid substitutions exhibited higher colistin resistance (MICs ≥512 mg/L) than did colistin-resistant strains encoding mutant MgrB, PmrB or PhoQ. Objectives CrrAB may regulate another unknown mechanism(s) contributing to colistin resistance, besides modifications of LPS with 4-amino-4-deoxy-l-arabinose and phosphoethanolamine. Methods To identify these potential unknown mechanism(s), a transposon mutant library of A4528 crrB(N141I) was constructed. Loci that might contribute to colistin resistance and were regulated by crrB were confirmed by deletion and complementation experiments. Results Screening of 2976 transposon mutants identified 47 mutants in which the MICs of colistin were significantly decreased compared with that for the parent. Besides crrAB, crrC and pmrHFIJKLM operons, these 47 transposon insertion mutants included another 13 loci. Notably, transcript levels of one of these insertion targets, H239_3064 (encoding a putative RND-type efflux pump), were significantly increased in A4528 crrB(N141I) compared with the A4528 parent strain. Deletion of H239_3064 in the A4528 crrB(N141I) background resulted in an 8-fold decrease in the MIC of colistin; complementation of the deletion mutant with H239_3064 restored resistance to colistin. Susceptibilities of A4528-derived strains to other antibiotics were also tested. Mutations of crrB resulted in decreased susceptibility to tetracycline and tigecycline, and deletion of H239_3064 in A4528 crrB(N141I) attenuated this phenomenon. Conclusions This study demonstrated that missense mutations of K. pneumoniae crrB lead to increased expression of H239_3064, leading in turn to decreased susceptibility to colistin, tetracycline and tigecycline.
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Affiliation(s)
- Yi-Hsiang Cheng
- Department of Microbiology, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Tzu-Lung Lin
- Department of Microbiology, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Yi-Tsung Lin
- Division of Infectious Diseases, Department of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan.,Institute of Emergency and Critical Care Medicine, National Yang-Ming University, Taipei, Taiwan
| | - Jin-Town Wang
- Department of Microbiology, National Taiwan University College of Medicine, Taipei, Taiwan.,Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan
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Laudadio E, Cedraro N, Mangiaterra G, Citterio B, Mobbili G, Minnelli C, Bizzaro D, Biavasco F, Galeazzi R. Natural Alkaloid Berberine Activity against Pseudomonas aeruginosa MexXY-Mediated Aminoglycoside Resistance: In Silico and in Vitro Studies. JOURNAL OF NATURAL PRODUCTS 2019; 82:1935-1944. [PMID: 31274312 DOI: 10.1021/acs.jnatprod.9b00317] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The multidrug efflux system MexXY-OprM, inside the resistance-nodulation-division family, is a major determinant of aminoglycoside resistance in Pseudomonas aeruginosa. In the fight aimed to identify potential efflux pump inhibitors among natural compounds, the alkaloid berberine emerged as a putative inhibitor of MexXY-OprM. In this work, we elucidated its interaction with the extrusor protein MexY and assessed its synergistic activity with aminoglycosides. In particular, we built an in silico model for the MexY protein in its trimeric association using both AcrB (E. coli) and MexB (P. aeruginosa) as 3D templates. This model has been stabilized in the bacterial cytoplasmic membrane using a molecular dynamics approach and used for ensemble docking to obtain the binding site mapping. Then, through dynamic docking, we assessed its binding affinity and its synergism with aminoglycosides focusing on tobramycin, which is widely used in the treatment of pulmonary infections. In vitro assays validated the data obtained: the results showed a 2-fold increase of the inhibitory activity and 2-4 log increase of the killing activity of the association berberine-tobramycin compared to those of tobramycin alone against 13/28 tested P. aeruginosa clinical isolates. From hemolytic assays, we preliminarily assessed berberine's low toxicity.
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Affiliation(s)
- Emiliano Laudadio
- Dipartimento S.I.M.A.U. , Università Politecnica delle Marche , Via Brecce Bianche , 60131 , Ancona , Italy
| | - Nicholas Cedraro
- Dipartimento di Scienze della Vita e dell'Ambiente , Università Politecnica delle Marche , Via Brecce Bianche , 60131 , Ancona , Italy
| | - Gianmarco Mangiaterra
- Dipartimento di Scienze della Vita e dell'Ambiente , Università Politecnica delle Marche , Via Brecce Bianche , 60131 , Ancona , Italy
| | - Barbara Citterio
- Dipartimento di Scienze Biomolecolari, sez. di Biotecnologie , Università degli Studi di Urbino "Carlo Bo" , 61029 , Urbino , Italy
| | - Giovanna Mobbili
- Dipartimento di Scienze della Vita e dell'Ambiente , Università Politecnica delle Marche , Via Brecce Bianche , 60131 , Ancona , Italy
| | - Cristina Minnelli
- Dipartimento di Scienze della Vita e dell'Ambiente , Università Politecnica delle Marche , Via Brecce Bianche , 60131 , Ancona , Italy
| | - Davide Bizzaro
- Dipartimento di Scienze della Vita e dell'Ambiente , Università Politecnica delle Marche , Via Brecce Bianche , 60131 , Ancona , Italy
| | - Francesca Biavasco
- Dipartimento di Scienze della Vita e dell'Ambiente , Università Politecnica delle Marche , Via Brecce Bianche , 60131 , Ancona , Italy
| | - Roberta Galeazzi
- Dipartimento di Scienze della Vita e dell'Ambiente , Università Politecnica delle Marche , Via Brecce Bianche , 60131 , Ancona , Italy
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Abstract
Resistance-nodulation-cell division multidrug efflux pumps are membrane proteins that catalyze the export of drugs and toxic compounds out of bacterial cells. Within the hydrophobe-amphiphile subfamily, these multidrug-resistant proteins form trimeric efflux pumps. The drug efflux process is energized by the influx of protons. Here, we use single-particle cryo-electron microscopy to elucidate the structure of the Acinetobacter baumannii AdeB multidrug efflux pump embedded in lipidic nanodiscs to a resolution of 2.98 Å. We found that each AdeB molecule within the trimer preferentially takes the resting conformational state in the absence of substrates. We propose that proton influx and drug efflux are synchronized and coordinated within the transport cycle.IMPORTANCE Acinetobacter baumannii is a successful human pathogen which has emerged as one of the most problematic and highly antibiotic-resistant Gram-negative bacteria worldwide. Multidrug efflux is a major mechanism that A. baumannii uses to counteract the action of multiple classes of antibiotics, such as β-lactams, tetracyclines, fluoroquinolones, and aminoglycosides. Here, we report a cryo-electron microscopy (cryo-EM) structure of the prevalent A. baumannii AdeB multidrug efflux pump, which indicates a plausible pathway for multidrug extrusion. Overall, our data suggest a mechanism for energy coupling that powers up this membrane protein to export antibiotics from bacterial cells. Our studies will ultimately inform an era in structure-guided drug design to combat multidrug resistance in these Gram-negative pathogens.
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40
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Atzori A, Malloci G, Prajapati JD, Basciu A, Bosin A, Kleinekathöfer U, Dreier J, Vargiu AV, Ruggerone P. Molecular Interactions of Cephalosporins with the Deep Binding Pocket of the RND Transporter AcrB. J Phys Chem B 2019; 123:4625-4635. [PMID: 31070373 PMCID: PMC6939625 DOI: 10.1021/acs.jpcb.9b01351] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The drug/proton antiporter AcrB, part of the major efflux pump AcrABZ-TolC in Escherichia coli, is characterized by its impressive ability to transport chemically diverse compounds, conferring a multidrug resistance phenotype. However, the molecular features differentiating between good and poor substrates of the pump have yet to be identified. In this work, we combined molecular docking with molecular dynamics simulations to study the interactions between AcrB and two representative cephalosporins, cefepime and ceftazidime (a good and poor substrate of AcrB, respectively). Our analysis revealed different binding preferences of the two compounds toward the subsites of the large deep binding pocket of AcrB. Cefepime, although less hydrophobic than ceftazidime, showed a higher affinity than ceftazidime for the so-called hydrophobic trap, a region known for binding inhibitors and substrates. This supports the hypothesis that surface complementarity between the molecule and AcrB, more than the intrinsic hydrophobicity of the antibiotic, is a feature required for the interaction within this region. Oppositely, the preference of ceftazidime for binding outside the hydrophobic trap might not be optimal for triggering allosteric conformational changes needed to the transporter to accomplish its function. Altogether, our findings could provide valuable information for the design of new antibiotics less susceptible to the efflux mechanism.
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Affiliation(s)
- Alessio Atzori
- Department of Physics, University of Cagliari, 09042 Monserrato (CA), Italy
| | - Giuliano Malloci
- Department of Physics, University of Cagliari, 09042 Monserrato (CA), Italy
| | | | - Andrea Basciu
- Department of Physics, University of Cagliari, 09042 Monserrato (CA), Italy
| | - Andrea Bosin
- Department of Physics, University of Cagliari, 09042 Monserrato (CA), Italy
| | - Ulrich Kleinekathöfer
- Department of Physics and Earth Sciences, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany
| | - Jürg Dreier
- Basilea Pharmaceutica International Ltd., Grenzacherstrasse 487, 4058 Basel, Switzerland
| | - Attilio V. Vargiu
- Department of Physics, University of Cagliari, 09042 Monserrato (CA), Italy
| | - Paolo Ruggerone
- Department of Physics, University of Cagliari, 09042 Monserrato (CA), Italy
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Lamut A, Peterlin Mašič L, Kikelj D, Tomašič T. Efflux pump inhibitors of clinically relevant multidrug resistant bacteria. Med Res Rev 2019; 39:2460-2504. [PMID: 31004360 DOI: 10.1002/med.21591] [Citation(s) in RCA: 109] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Revised: 03/31/2019] [Accepted: 04/02/2019] [Indexed: 12/29/2022]
Abstract
Bacterial infections are an increasingly serious issue worldwide. The inability of existing therapies to treat multidrug-resistant pathogens has been recognized as an important challenge of the 21st century. Efflux pumps are important in both intrinsic and acquired bacterial resistance and identification of small molecule efflux pump inhibitors (EPIs), capable of restoring the effectiveness of available antibiotics, is an active research field. In the last two decades, much effort has been made to identify novel EPIs. However, none of them has so far been approved for therapeutic use. In this article, we explore different structural families of currently known EPIs for multidrug resistance efflux systems in the most extensively studied pathogens (NorA in Staphylococcus aureus, AcrAB-TolC in Escherichia coli, and MexAB-OprM in Pseudomonas aeruginosa). Both synthetic and natural compounds are described, with structure-activity relationship studies and optimization processes presented systematically for each family individually. In vitro activities against selected test strains are presented in a unifying manner for all the EPIs described, together with the most important toxicity, pharmacokinetic and in vivo efficacy data. A critical evaluation of lead-likeness characteristics and the potential for clinical development of the most promising inhibitors of the three efflux systems is described. This overview of EPIs is a good starting point for the identification of novel effective antibacterial drugs.
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Affiliation(s)
- Andraž Lamut
- Chair of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Ljubljana, Ljubljana, Slovenia
| | - Lucija Peterlin Mašič
- Chair of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Ljubljana, Ljubljana, Slovenia
| | - Danijel Kikelj
- Chair of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Ljubljana, Ljubljana, Slovenia
| | - Tihomir Tomašič
- Chair of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Ljubljana, Ljubljana, Slovenia
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Crystal structures of multidrug efflux pump MexB bound with high-molecular-mass compounds. Sci Rep 2019; 9:4359. [PMID: 30867446 PMCID: PMC6416280 DOI: 10.1038/s41598-019-40232-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Accepted: 02/07/2019] [Indexed: 12/27/2022] Open
Abstract
RND-type multidrug efflux pumps have two voluminous multisite drug-binding pockets named the proximal and distal binding pocket. High- and low-molecular-mass drugs bind to these proximal and distal pocket, respectively. Here, we report the crystal structures of MexB of Pseudomonas aeruginosa bound with high-molecular-mass compounds. Contrary to the expectations, lauryl maltose neopentyl glycol (LMNG, MW 1,005), which is a surfactant larger than the proximal pocket-binding drugs, was found to bind to the distal pocket: one of the two hydrophobic alkyl chains was inserted into the hydrophobic pit, which is the binding site of the efflux pump inhibitor ABI-PP. LMNG is a substrate of the MexAB-OprM system and competitively inhibits the export of other substrates by this system. However, LMNG does not inhibit the export of other substrates by the inhibitor-binding-pit mutant F178W, which retains the export activity of LMNG. The crystal structure of this mutant suggested that the alkyl chain of LMNG could no longer be inserted into the pit because of steric hindrance. We also determined the crystal structure of MexB containing the high-molecular-mass compound neopentyl glycol derivative C7NG (MW 1,028), the binding site of which overlapped with LMNG in the distal pocket, indicating that whether a substrate binds to the distal or proximal pockets is controlled not only by its molecular weight but also by its individual molecular characteristic.
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Proof of an Outer Membrane Target of the Efflux Inhibitor Phe-Arg-β-Naphthylamide from Random Mutagenesis. Molecules 2019; 24:molecules24030470. [PMID: 30699887 PMCID: PMC6384556 DOI: 10.3390/molecules24030470] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Revised: 01/24/2019] [Accepted: 01/25/2019] [Indexed: 12/17/2022] Open
Abstract
Phe-Arg-β-naphthylamide (PAβN) has been characterized as an efflux pump inhibitor (EPI) acting on the major multidrug resistance efflux transporters of Gram-negative bacteria, such as AcrB in Eschericha coli. In the present study, in vitro random mutagenesis was used to evolve resistance to the sensitizing activity of PAβN with the aim of elucidating its mechanism of action. A strain was obtained that was phenotypically similar to a previously reported mutant from a serial selection approach that had no efflux-associated mutations. We could confirm that acrB mutations in the new mutant were unrelated to PAβN resistance. The next-generation sequencing of the two mutants revealed loss-of-function mutations in lpxM. An engineered lpxM knockout strain showed up to 16-fold decreased PAβN activity with large lipophilic drugs, while its efflux capacity, as well as the efficacy of other EPIs, remained unchanged. LpxM is responsible for the last acylation step in lipopolysaccharide (LPS) synthesis, and lpxM deficiency has been shown to result in penta-acylated instead of hexa-acylated lipid A. Modeling the two lipid A types revealed steric conformational changes due to underacylation. The findings provide evidence of a target site of PAβN in the LPS layer, and prove membrane activity contributing to its drug-sensitizing potency.
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44
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Atzori A, Malviya VN, Malloci G, Dreier J, Pos KM, Vargiu AV, Ruggerone P. Identification and characterization of carbapenem binding sites within the RND-transporter AcrB. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1861:62-74. [PMID: 30416087 DOI: 10.1016/j.bbamem.2018.10.012] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Revised: 10/19/2018] [Accepted: 10/22/2018] [Indexed: 12/11/2022]
Abstract
Understanding the molecular determinants for recognition, binding and transport of antibiotics by multidrug efflux systems is important for basic research and useful for the design of more effective antimicrobial compounds. Imipenem and meropenem are two carbapenems whose antibacterial activity is known to be poorly and strongly affected by MexAB-OprM, the major efflux pump transporter in Pseudomonas aeruginosa. However, not much is known regarding recognition and transport of these compounds by AcrAB-TolC, which is the MexAB-OprM homologue in Escherichia coli and by definition the paradigm model for structural studies on efflux pumps. Prompted by this motivation, we unveiled the molecular details of the interaction of imipenem and meropenem with the transporter AcrB by combining computer simulations with biophysical experiments. Regarding the interaction with the two main substrate binding regions of AcrB, the so-called access and deep binding pockets, molecular dynamics simulations revealed imipenem to be more mobile than meropenem in the former, while comparable mobilities were observed in the latter. This result is in line with isothermal titration calorimetry, differential scanning experiments, and binding free energy calculations, indicating a higher affinity for meropenem than imipenem at the deep binding pocket, while both sharing similar affinities at the access pocket. Our findings rationalize how different physico-chemical properties of compounds reflect on their interactions with AcrB. As such, they constitute precious information to be exploited for the rational design of antibiotics able to evade efflux pumps.
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Affiliation(s)
- Alessio Atzori
- Department of Physics, University of Cagliari, 09042 Monserrato, CA, Italy
| | - Viveka N Malviya
- Institute of Biochemistry, Goethe University Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany
| | - Giuliano Malloci
- Department of Physics, University of Cagliari, 09042 Monserrato, CA, Italy
| | - Jürg Dreier
- Basilea Pharmaceutica International Ltd., Grenzacherstrasse 487, 4058 Basel, Switzerland
| | - Klaas M Pos
- Institute of Biochemistry, Goethe University Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany
| | - Attilio V Vargiu
- Department of Physics, University of Cagliari, 09042 Monserrato, CA, Italy
| | - Paolo Ruggerone
- Department of Physics, University of Cagliari, 09042 Monserrato, CA, Italy,.
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Masi M, Dumont E, Vergalli J, Pajovic J, Réfrégiers M, Pagès JM. Fluorescence enlightens RND pump activity and the intrabacterial concentration of antibiotics. Res Microbiol 2018; 169:432-441. [DOI: 10.1016/j.resmic.2017.11.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Revised: 11/22/2017] [Accepted: 11/23/2017] [Indexed: 02/01/2023]
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46
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Kang MK, Tullman-Ercek D. Engineering expression and function of membrane proteins. Methods 2018; 147:66-72. [DOI: 10.1016/j.ymeth.2018.04.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2018] [Revised: 04/03/2018] [Accepted: 04/16/2018] [Indexed: 01/18/2023] Open
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Mapping the Dynamic Functions and Structural Features of AcrB Efflux Pump Transporter Using Accelerated Molecular Dynamics Simulations. Sci Rep 2018; 8:10470. [PMID: 29992991 PMCID: PMC6041327 DOI: 10.1038/s41598-018-28531-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Accepted: 06/25/2018] [Indexed: 11/08/2022] Open
Abstract
Multidrug efflux pumps confer resistance to their bacterial hosts by pumping out a diverse range of compounds, including most antibiotics. Being more familiar with the details of functional dynamics and conformations of these types of pumps could help in discovering approaches to stop them functioning properly. Computational approaches, particularly conventional molecular dynamics simulations followed by diverse post simulation analysis, are powerful methods that help researchers by opening a new window to study phenomena that are not detectable in as much detail in vitro or in vivo as they are in silico. In this study, accelerated molecular dynamics simulations were applied to study the dynamics of AcrB efflux pump transporters in interaction with PAβN and tetracycline as an inhibitor and a substrate, respectively, to compare the differences in the dynamics and consequently the mechanism of action of the pump. The different dynamics for PAβN -bound form of AcrB compared to the TET-bound form is likely to affect the rotating mechanism typically observed for AcrB transporter. This shows the dynamics of the active AcrB transporter is different in a substrate-bound state compared to an inhibitor-bound state. This advances our knowledge and helps to unravel the mechanism of tripartite efflux pumps.
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Nitrothiophene carboxamides, a novel narrow spectrum antibacterial series: Mechanism of action and Efficacy. Sci Rep 2018; 8:7263. [PMID: 29740005 PMCID: PMC5940854 DOI: 10.1038/s41598-018-25407-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Accepted: 04/20/2018] [Indexed: 12/24/2022] Open
Abstract
The mechanism of efflux is a tour-de-force in the bacterial armoury that has thwarted the development of novel antibiotics. We report the discovery of a novel chemical series with potent antibacterial properties that was engineered to overcome efflux liability. Compounds liable to efflux specifically via the Resistance Nodulation and cell Division (RND) pump, AcrAB-TolC were chosen for a hit to lead progression. Using structure-based design, the compounds were optimised to lose their binding to the efflux pump, thereby making them potent on wild-type bacteria. We discovered these compounds to be pro-drugs that require activation in E. coli by specific bacterial nitroreductases NfsA and NfsB. Hit to lead chemistry led to the generation of compounds that were potent on wild-type and multi-drug resistant clinical isolates of E. coli, Shigella spp., and Salmonella spp. These compounds are bactericidal and efficacious in a mouse thigh infection model.
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Haynes MK, Garcia M, Peters R, Waller A, Tedesco P, Ursu O, Bologa CG, Santos RG, Pinilla C, Wu TH, Lovchik JA, Oprea TI, Sklar LA, Tegos GP. High-Throughput Flow Cytometry Screening of Multidrug Efflux Systems. Methods Mol Biol 2018; 1700:293-318. [PMID: 29177837 DOI: 10.1007/978-1-4939-7454-2_16] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The resistance nodulation cell division (RND) family of proteins are inner membrane transporters that associate with periplasmic adaptor proteins and outer membrane porins to affect substrate transport from the cytosol and periplasm in Gram-negative bacteria. Various structurally diverse compounds are substrates of RND transporters. Along with their notable role in antibiotic resistance, these transporters are essential for niche colonization, quorum sensing, and virulence as well as for the removal of fatty acids and bile salts. As such, RNDs are an attractive target for antimicrobial development. However, while enhancing the utility of antibiotics with an RND inhibitor is an appealing concept, only a small core of chemotypes has been identified as efflux pump inhibitors (EPIs). Thus, our key objective is the development and validation of an efflux profiling and discovery strategy for RND model systems. Here we describe a flow cytometric dye accumulation assay that uses fluorescein diacetate (FDA) to interrogate the model Gram-negative pathogens Escherichia coli, Franscisella tularensis, and Burkholderia pseudomallei. Fluorochrome retention is increased in the presence of known efflux inhibitors and in RND deletion strains. The assay can be used in a high-throughput format to evaluate efflux of dye-substrate candidates and to screen chemical libraries for novel EPIs. Triaged compounds that inhibit efflux in pathogenic strains are tested for growth inhibition and antibiotic potentiation using microdilution culture plates in a select agent Biosafety Level-3 (BSL3) environment. This combined approach demonstrates the utility of flow cytometric analysis for efflux activity and provides a useful platform in which to characterize efflux in pathogenic Gram-negative bacteria. Screening small molecule libraries for novel EPI candidates offers the potential for the discovery of new classes of antibacterial compounds.
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Affiliation(s)
- Mark K Haynes
- Center for Molecular Discovery, University of New Mexico School of Medicine, Albuquerque, NM, USA.
- Department of Pathology, University of New Mexico School of Medicine, Albuquerque, NM, USA.
| | - Matthew Garcia
- Center for Molecular Discovery, University of New Mexico School of Medicine, Albuquerque, NM, USA
- Department of Pathology, University of New Mexico School of Medicine, Albuquerque, NM, USA
| | - Ryan Peters
- Center for Infectious Disease and Immunity, Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM, USA
| | - Anna Waller
- Center for Molecular Discovery, University of New Mexico School of Medicine, Albuquerque, NM, USA
- Department of Pathology, University of New Mexico School of Medicine, Albuquerque, NM, USA
| | - Pietro Tedesco
- Institute of Protein Biochemistry, National Research Council, Naples, Italy
- Department of Chemical Sciences and School of Biotechnological Sciences, University of Naples, Naples, Italy
| | - Oleg Ursu
- Division of Translational Informatics, Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM, USA
| | - Cristian G Bologa
- Division of Translational Informatics, Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM, USA
| | - Radleigh G Santos
- Torrey Pines Institute for Molecular Studies, Port St Lucie, FL, USA
| | | | - Terry H Wu
- Center for Infectious Disease and Immunity, Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM, USA
| | - Julie A Lovchik
- Center for Infectious Disease and Immunity, Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM, USA
| | - Tudor I Oprea
- Division of Translational Informatics, Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM, USA
| | - Larry A Sklar
- Center for Molecular Discovery, University of New Mexico School of Medicine, Albuquerque, NM, USA
- Department of Pathology, University of New Mexico School of Medicine, Albuquerque, NM, USA
| | - George P Tegos
- Department of Dermatology, Harvard Medical School, Boston, MA, USA.
- Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, MA, USA.
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50
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Naseem S, Khalid M, Tahir MN, Halim MA, Braga AA, Naseer MM, Shafiq Z. Synthesis, structural, DFT studies, docking and antibacterial activity of a xanthene based hydrazone ligand. J Mol Struct 2017. [DOI: 10.1016/j.molstruc.2017.04.093] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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