1
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Varela MF, Ortiz-Alegria A, Lekshmi M, Stephen J, Kumar S. Functional Roles of the Conserved Amino Acid Sequence Motif C, the Antiporter Motif, in Membrane Transporters of the Major Facilitator Superfamily. BIOLOGY 2023; 12:1336. [PMID: 37887046 PMCID: PMC10604125 DOI: 10.3390/biology12101336] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Revised: 10/09/2023] [Accepted: 10/10/2023] [Indexed: 10/28/2023]
Abstract
The biological membrane surrounding all living cells forms a hydrophobic barrier to the passage of biologically important molecules. Integral membrane proteins called transporters circumvent the cellular barrier and transport molecules across the cell membrane. These molecular transporters enable the uptake and exit of molecules for cell growth and homeostasis. One important collection of related transporters is the major facilitator superfamily (MFS). This large group of proteins harbors passive and secondary active transporters. The transporters of the MFS consist of uniporters, symporters, and antiporters, which share similarities in structures, predicted mechanism of transport, and highly conserved amino acid sequence motifs. In particular, the antiporter motif, called motif C, is found primarily in antiporters of the MFS. The antiporter motif's molecular elements mediate conformational changes and other molecular physiological roles during substrate transport across the membrane. This review article traces the history of the antiporter motif. It summarizes the physiological evidence reported that supports these biological roles.
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Affiliation(s)
- Manuel F. Varela
- Department of Biology, Eastern New Mexico University, Portales, NM 88130, USA;
| | - Anely Ortiz-Alegria
- Department of Biology, Eastern New Mexico University, Portales, NM 88130, USA;
| | - Manjusha Lekshmi
- ICAR-Central Institute of Fisheries Education (CIFE), Mumbai 400061, India; (M.L.); (J.S.); (S.K.)
| | - Jerusha Stephen
- ICAR-Central Institute of Fisheries Education (CIFE), Mumbai 400061, India; (M.L.); (J.S.); (S.K.)
| | - Sanath Kumar
- ICAR-Central Institute of Fisheries Education (CIFE), Mumbai 400061, India; (M.L.); (J.S.); (S.K.)
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2
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Comparison of Phenotype and Genotype Virulence and Antimicrobial Factors of Salmonella Typhimurium Isolated from Human Milk. Int J Mol Sci 2023; 24:ijms24065135. [PMID: 36982209 PMCID: PMC10048834 DOI: 10.3390/ijms24065135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Revised: 03/03/2023] [Accepted: 03/04/2023] [Indexed: 03/11/2023] Open
Abstract
Salmonella is a common foodborne infection. Many serovars belonging to Salmonella enterica subsp. enterica are present in the gut of various animal species. They can cause infection in human infants via breast milk or cross-contamination with powdered milk. In the present study, Salmonella BO was isolated from human milk in accordance with ISO 6579-1:2017 standards and sequenced using whole-genome sequencing (WGS), followed by serosequencing and genotyping. The results also allowed its pathogenicity to be predicted. The WGS results were compared with the bacterial phenotype. The isolated strain was found to be Salmonella enterica subsp. enterica serovar Typhimurium 4:i:1,2_69M (S. Typhimurium 69M); it showed a very close similarity to S. enterica subsp. enterica serovar Typhimurium LT2. Bioinformatics sequence analysis detected eleven SPIs (SPI-1, SPI-2, SPI-3, SPI-4, SPI-5, SPI-9, SPI-12, SPI-13, SPI-14, C63PI, CS54_island). Significant changes in gene sequences were noted, causing frameshift mutations in yeiG, rfbP, fumA, yeaL, ybeU (insertion) and lpfD, avrA, ratB, yacH (deletion). The sequences of several proteins were significantly different from those coded in the reference genome; their three-dimensional structure was predicted and compared with reference proteins. Our findings indicate the presence of a number of antimicrobial resistance genes that do not directly imply an antibiotic resistance phenotype.
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3
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Behruznia M, Gordon DM. Molecular and metabolic characteristics of wastewater associated Escherichia coli strains. ENVIRONMENTAL MICROBIOLOGY REPORTS 2022; 14:646-654. [PMID: 35638456 PMCID: PMC9543349 DOI: 10.1111/1758-2229.13076] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Accepted: 04/18/2022] [Indexed: 06/04/2023]
Abstract
We previously characterized the genetic diversity of Escherichia coli strains isolated from septic tanks in the Canberra region, Australia. In this study, we used repetitive element palindromic (REP) PCR fingerprinting to identify dominant REP-types belonging to phylogroups A and B1 strains across septic tanks. Subsequently, 76 E. coli strains were selected for whole-genome sequencing and phenotype microarrays. Comparative genome analysis was performed to compare septic tank E. coli genomes with a collection of 433 E. coli isolates from different hosts and freshwater. Clonal complexes (CCs) 10 (n = 15) and 399 (n = 10) along with sequence type (ST) 401 (n = 9) were the common lineages in septic tanks. CC10 strains have been detected from animal hosts and freshwater, whereas CC399 and ST401 strains appeared to be associated with septic tanks as they were uncommon in isolates from other sources. Comparative genome analysis revealed that CC399 and ST401 were genetically distinct from other isolates and carried an abundance of niche-specific traits involved in environmental adaptation. These strains also showed distinct metabolic characteristics, such as the ability to utilize pectin, which may provide a fitness advantage under nutrient-limited conditions. The results of this study characterized the adaptive mechanisms allowing E. coli to persist in wastewater.
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Affiliation(s)
- Mahboobeh Behruznia
- Division of Ecology and Evolution, Research School of BiologyThe Australian National UniversityCanberraACT2601Australia
| | - David M. Gordon
- Division of Ecology and Evolution, Research School of BiologyThe Australian National UniversityCanberraACT2601Australia
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4
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Draft Genome Sequences of Multidrug-Resistant Shiga Toxin-Producing Escherichia coli O116:H25 Strains from Ready-to-Eat Foods Sold in Lagos, Nigeria. Microbiol Resour Announc 2022; 11:e0031422. [PMID: 35862915 PMCID: PMC9387260 DOI: 10.1128/mra.00314-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Draft genomes of multidrug-resistant Shiga toxin-producing Escherichia coli (STEC) strains IPK9(1) and IKS1(2), which were isolated from ready-to-eat foods (kokoro and shawarma) sold in Lagos, Nigeria, are reported. The genomes possessed genetic determinants for virulence and the antibiotic resistance gene for macrolide-associated resistance mdf(A). Ready-to-eat foods increase public health threats in Nigeria.
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5
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Garcia ÍR, de Oliveira Garcia FA, Pereira PS, Coutinho HDM, Siyadatpanah A, Norouzi R, Wilairatana P, de Lourdes Pereira M, Nissapatorn V, Tintino SR, Rodrigues FFG. Microbial resistance: The role of efflux pump superfamilies and their respective substrates. Life Sci 2022; 295:120391. [PMID: 35149116 DOI: 10.1016/j.lfs.2022.120391] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2021] [Revised: 02/02/2022] [Accepted: 02/06/2022] [Indexed: 12/24/2022]
Abstract
The microorganism resistance to antibiotics has become one of the most worrying issues for science due to the difficulties related to clinical treatment and the rapid spread of diseases. Efflux pumps are classified into six groups of carrier proteins that are part of the different types of mechanisms that contribute to resistance in microorganisms, allowing their survival. The present study aimed to carry out a bibliographic review on the superfamilies of carriers in order to understand their compositions, expressions, substrates, and role in intrinsic resistance. At first, a search for manuscripts was carried out in the databases Medline, Pubmed, ScienceDirect, and Scielo, using as descriptors: efflux pump, expression, pump inhibitors and efflux superfamily. For article selection, two criteria were taken into account: for inclusion, those published between 2000 and 2020, including textbooks, and for exclusion, duplicates and academic collections. In this research, 139,615 published articles were obtained, with 312 selected articles and 7 book chapters that best met the aim. From the comprehensive analysis, it was possible to consider that the chromosomes and genetic elements can contain genes encoding efflux pumps and are responsible for multidrug resistance. Even though this is a well-explored topic in the scientific community, understanding the behavior of antibiotics as substrates that increase the expression of pump-encoding genes has challenged medicine. This review study succinctly summarizes the most relevant features of these systems, as well as their contribution to multidrug resistance.
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Affiliation(s)
| | | | | | | | - Abolghasem Siyadatpanah
- Ferdows School of Paramedical and Health, Birjand University of Medical Sciences, Birjand, Iran
| | - Roghayeh Norouzi
- Department of Pathobiology, Faculty of Veterinary Medicine, University of Tabriz, Tabriz, Iran
| | - Polrat Wilairatana
- Department of Clinical Tropical Medicine, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
| | - Maria de Lourdes Pereira
- CICECO-Aveiro Institute of Materials & Department of Medical Sciences, University of Aveiro, 3810-193 Aveiro, Portugal
| | - Veeranoot Nissapatorn
- School of Allied Health Sciences and Research Excellence Center for Innovation and Health, Walailak University, Thailand
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6
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Bahrenberg T, Yardeni EH, Feintuch A, Bibi E, Goldfarb D. Substrate binding in the multidrug transporter MdfA in detergent solution and in lipid nanodiscs. Biophys J 2021; 120:1984-1993. [PMID: 33771471 PMCID: PMC8204392 DOI: 10.1016/j.bpj.2021.03.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Revised: 03/07/2021] [Accepted: 03/15/2021] [Indexed: 10/21/2022] Open
Abstract
MdfA from Escherichia coli is a prototypical secondary multi-drug (Mdr) transporter that exchanges drugs for protons. MdfA-mediated drug efflux is driven by the proton gradient and enabled by conformational changes that accompany the recruitment of drugs and their release. In this work, we applied distance measurements by W-band double electron-electron resonance (DEER) spectroscopy to explore the binding of mito-TEMPO, a nitroxide-labeled substrate analog, to Gd(III)-labeled MdfA. The choice of Gd(III)-nitroxide DEER enabled measurements in the presence of excess of mito-TEMPO, which has a relatively low affinity to MdfA. Distance measurements between mito-TEMPO and MdfA labeled at the periplasmic edges of either of three selected transmembrane helices (TM3101, TM5168, and TM9310) revealed rather similar distance distributions in detergent micelles (n-dodecyl-β-d-maltopyranoside, DDM)) and in lipid nanodiscs (ND). By grafting the predicted positions of the Gd(III) tag on the inward-facing (If) crystal structure, we looked for binding positions that reproduced the maxima of the distance distributions. The results show that the location of the mito-TEMPO nitroxide in DDM-solubilized or ND-reconstituted MdfA is similar (only 0.4 nm apart). In both cases, we located the nitroxide moiety near the ligand binding pocket in the If structure. However, according to the DEER-derived position, the substrate clashes with TM11, suggesting that for mito-TEMPO-bound MdfA, TM11 should move relative to the If structure. Additional DEER studies with MdfA labeled with Gd(III) at two sites revealed that TM9 also dislocates upon substrate binding. Together with our previous reports, this study demonstrates the utility of Gd(III)-Gd(III) and Gd(III)-nitroxide DEER measurements for studying the conformational behavior of transporters.
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Affiliation(s)
- Thorsten Bahrenberg
- Departments of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Eliane Hadas Yardeni
- Departments of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Akiva Feintuch
- Departments of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Eitan Bibi
- Departments of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel.
| | - Daniella Goldfarb
- Departments of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel.
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7
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Rybenkov VV, Zgurskaya HI, Ganguly C, Leus IV, Zhang Z, Moniruzzaman M. The Whole Is Bigger than the Sum of Its Parts: Drug Transport in the Context of Two Membranes with Active Efflux. Chem Rev 2021; 121:5597-5631. [PMID: 33596653 DOI: 10.1021/acs.chemrev.0c01137] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Cell envelope plays a dual role in the life of bacteria by simultaneously protecting it from a hostile environment and facilitating access to beneficial molecules. At the heart of this ability lie the restrictive properties of the cellular membrane augmented by efflux transporters, which preclude intracellular penetration of most molecules except with the help of specialized uptake mediators. Recently, kinetic properties of the cell envelope came into focus driven on one hand by the urgent need in new antibiotics and, on the other hand, by experimental and theoretical advances in studies of transmembrane transport. A notable result from these studies is the development of a kinetic formalism that integrates the Michaelis-Menten behavior of individual transporters with transmembrane diffusion and offers a quantitative basis for the analysis of intracellular penetration of bioactive compounds. This review surveys key experimental and computational approaches to the investigation of transport by individual translocators and in whole cells, summarizes key findings from these studies and outlines implications for antibiotic discovery. Special emphasis is placed on Gram-negative bacteria, whose envelope contains two separate membranes. This feature sets these organisms apart from Gram-positive bacteria and eukaryotic cells by providing them with full benefits of the synergy between slow transmembrane diffusion and active efflux.
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Affiliation(s)
- Valentin V Rybenkov
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
| | - Helen I Zgurskaya
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
| | - Chhandosee Ganguly
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
| | - Inga V Leus
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
| | - Zhen Zhang
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
| | - Mohammad Moniruzzaman
- Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019, United States
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8
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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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9
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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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10
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Kell DB. A protet-based, protonic charge transfer model of energy coupling in oxidative and photosynthetic phosphorylation. Adv Microb Physiol 2021; 78:1-177. [PMID: 34147184 DOI: 10.1016/bs.ampbs.2021.01.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Textbooks of biochemistry will explain that the otherwise endergonic reactions of ATP synthesis can be driven by the exergonic reactions of respiratory electron transport, and that these two half-reactions are catalyzed by protein complexes embedded in the same, closed membrane. These views are correct. The textbooks also state that, according to the chemiosmotic coupling hypothesis, a (or the) kinetically and thermodynamically competent intermediate linking the two half-reactions is the electrochemical difference of protons that is in equilibrium with that between the two bulk phases that the coupling membrane serves to separate. This gradient consists of a membrane potential term Δψ and a pH gradient term ΔpH, and is known colloquially as the protonmotive force or pmf. Artificial imposition of a pmf can drive phosphorylation, but only if the pmf exceeds some 150-170mV; to achieve in vivo rates the imposed pmf must reach 200mV. The key question then is 'does the pmf generated by electron transport exceed 200mV, or even 170mV?' The possibly surprising answer, from a great many kinds of experiment and sources of evidence, including direct measurements with microelectrodes, indicates it that it does not. Observable pH changes driven by electron transport are real, and they control various processes; however, compensating ion movements restrict the Δψ component to low values. A protet-based model, that I outline here, can account for all the necessary observations, including all of those inconsistent with chemiosmotic coupling, and provides for a variety of testable hypotheses by which it might be refined.
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Affiliation(s)
- Douglas B Kell
- Department of Biochemistry and Systems Biology, Institute of Systems, Molecular and Integrative, Biology, University of Liverpool, Liverpool, United Kingdom; The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Lyngby, Denmark.
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11
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Xiao Q, Sun B, Zhou Y, Wang C, Guo L, He J, Deng D. Visualizing the nonlinear changes of a drug-proton antiporter from inward-open to occluded state. Biochem Biophys Res Commun 2020; 534:272-278. [PMID: 33280821 DOI: 10.1016/j.bbrc.2020.11.096] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Accepted: 11/24/2020] [Indexed: 11/24/2022]
Abstract
Drug-proton antiporters (DHA) play an important role in multi-drug resistance, utilizing the proton-motive force to drive the expulsion of toxic molecules, including antibiotics and drugs. DHA transporters belong to the major facilitator superfamily (MFS), members of which deliver substrates by utilizing the alternating access model of transport. However, the transport process is still elusive. Here, we report the structures of SotB, a member of DHA1 family (TCDB: 2.A.1.2) from Escherichia coli. Four crystal structures of SotB were captured in different conformations, including substrate-bound occluded, inward-facing, and inward-open states. Comparisons between the four structures reveal nonlinear rigid-body movements of alternating access during the state transition from inward-open to occluded conformation. This work not only reveals the conformational dynamics of SotB but also deepens our understanding of the alternating access mechanism of MFS transporters.
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Affiliation(s)
- Qingjie Xiao
- From the Division of Obstetrics, Key Laboratory of Birth Defects and Related Disease of Women and Children of MOE, State Key Laboratory of Biotherapy, West China Second Hospital, Sichuan University, Chengdu, 610041, China
| | - Bo Sun
- Shanghai Synchrotron Radiation Facility Science Center, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai, 201204, China
| | - Yanxia Zhou
- From the Division of Obstetrics, Key Laboratory of Birth Defects and Related Disease of Women and Children of MOE, State Key Laboratory of Biotherapy, West China Second Hospital, Sichuan University, Chengdu, 610041, China
| | - Chen Wang
- From the Division of Obstetrics, Key Laboratory of Birth Defects and Related Disease of Women and Children of MOE, State Key Laboratory of Biotherapy, West China Second Hospital, Sichuan University, Chengdu, 610041, China
| | - Li Guo
- From the Division of Obstetrics, Key Laboratory of Birth Defects and Related Disease of Women and Children of MOE, State Key Laboratory of Biotherapy, West China Second Hospital, Sichuan University, Chengdu, 610041, China
| | - Jianhua He
- Shanghai Synchrotron Radiation Facility Science Center, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai, 201204, China.
| | - Dong Deng
- From the Division of Obstetrics, Key Laboratory of Birth Defects and Related Disease of Women and Children of MOE, State Key Laboratory of Biotherapy, West China Second Hospital, Sichuan University, Chengdu, 610041, China.
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12
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Yardeni EH, Mishra S, Stein RA, Bibi E, Mchaourab HS. The Multidrug Transporter MdfA Deviates from the Canonical Model of Alternating Access of MFS Transporters. J Mol Biol 2020; 432:5665-5680. [PMID: 32860775 DOI: 10.1016/j.jmb.2020.08.017] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 08/18/2020] [Accepted: 08/19/2020] [Indexed: 02/06/2023]
Abstract
The prototypic multidrug (Mdr) transporter MdfA from Escherichia coli efflux chemically- dissimilar substrates in exchange for protons. Similar to other transporters, MdfA purportedly functions by alternating access of a central substrate binding pocket to either side of the membrane. Accordingly, MdfA should open at the cytoplasmic side and/or laterally toward the membrane to enable access of drugs into its pocket. At the end of the cycle, the periplasmic side is expected to open to release drugs. Two distinct conformations of MdfA have been captured by X-ray crystallography: An outward open (Oo) conformation, stabilized by a Fab fragment, and a ligand-bound inward-facing (If) conformation, possibly stabilized by a mutation (Q131R). Here, we investigated how these structures relate to ligand-dependent conformational dynamics of MdfA in lipid bilayers. For this purpose, we combined distances measured by double electron-electron resonance (DEER) between pairs of spin labels in MdfA, reconstituted in nanodiscs, with cysteine cross-linking of natively expressed membrane-embedded MdfA variants. Our results suggest that in a membrane environment, MdfA assumes a relatively flexible, outward-closed/inward-closed (Oc/Ic) conformation. Unexpectedly, our data show that neither the substrate TPP nor protonation induces large-scale conformational changes. Rather, we identified a substrate-responsive lateral gate, which is open toward the inner leaflet of the membrane but closes upon drug binding. Together, our results suggest a modified model for the functional conformational cycle of MdfA that does not invoke canonical elements of alternating access.
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Affiliation(s)
- Eliane H Yardeni
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Smriti Mishra
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, USA
| | - Richard A Stein
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, USA
| | - Eitan Bibi
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot 76100, Israel.
| | - Hassane S Mchaourab
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, USA.
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13
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Yardeni EH, Bahrenberg T, Stein RA, Mishra S, Zomot E, Graham B, Tuck KL, Huber T, Bibi E, Mchaourab HS, Goldfarb D. Probing the solution structure of the E. coli multidrug transporter MdfA using DEER distance measurements with nitroxide and Gd(III) spin labels. Sci Rep 2019; 9:12528. [PMID: 31467343 PMCID: PMC6715713 DOI: 10.1038/s41598-019-48694-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2019] [Accepted: 08/08/2019] [Indexed: 11/09/2022] Open
Abstract
Methodological and technological advances in EPR spectroscopy have enabled novel insight into the structural and dynamic aspects of integral membrane proteins. In addition to an extensive toolkit of EPR methods, multiple spin labels have been developed and utilized, among them Gd(III)-chelates which offer high sensitivity at high magnetic fields. Here, we applied a dual labeling approach, employing nitroxide and Gd(III) spin labels, in conjunction with Q-band and W-band double electron-electron resonance (DEER) measurements to characterize the solution structure of the detergent-solubilized multidrug transporter MdfA from E. coli. Our results identify highly flexible regions of MdfA, which may play an important role in its functional dynamics. Comparison of distance distribution of spin label pairs on the periplasm with those calculated using inward- and outward-facing crystal structures of MdfA, show that in detergent micelles, the protein adopts a predominantly outward-facing conformation, although more closed than the crystal structure. The cytoplasmic pairs suggest a small preference to the outward-facing crystal structure, with a somewhat more open conformation than the crystal structure. Parallel DEER measurements with the two types of labels led to similar distance distributions, demonstrating the feasibility of using W-band spectroscopy with a Gd(III) label for investigation of the structural dynamics of membrane proteins.
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Affiliation(s)
- Eliane H Yardeni
- Department of Biomolecular Sciences, Weizmann Institute of Science Rehovot, Rehovot, 76100, Israel
| | - Thorsten Bahrenberg
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Richard A Stein
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, USA
| | - Smriti Mishra
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, USA
| | - Elia Zomot
- Department of Biomolecular Sciences, Weizmann Institute of Science Rehovot, Rehovot, 76100, Israel
| | - Bim Graham
- Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC, 3052, Australia
| | - Kellie L Tuck
- School of Chemistry, Monash University, Wellington Road, Clayton, Victoria, Australia
| | - Thomas Huber
- Research School of Chemistry, The Australian National University, Canberra, ACT 2601, Australia
| | - Eitan Bibi
- Department of Biomolecular Sciences, Weizmann Institute of Science Rehovot, Rehovot, 76100, Israel.
| | - Hassane S Mchaourab
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, USA.
| | - Daniella Goldfarb
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, 76100, Israel.
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14
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Deletion of the major Escherichia coli multidrug transporter AcrB reveals transporter plasticity and redundancy in bacterial cells. PLoS One 2019; 14:e0218828. [PMID: 31251753 PMCID: PMC6599122 DOI: 10.1371/journal.pone.0218828] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2019] [Accepted: 06/11/2019] [Indexed: 12/28/2022] Open
Abstract
Multidrug Transporters (MDTs) are major contributors to the acquisition and maintenance of Antimicrobial Resistance (AMR), a growing public health threat of broad concern. Despite the large number of MDTs, the overwhelming majority of the studies performed thus far in Gram-negative bacteria emphasize the supremacy of the AcrAB-TolC complex. To unveil the potential role of other MDTs we studied the behavior of a null AcrB Escherichia coli strain when challenged with chloramphenicol, a bacteriostatic antibiotic. We found that such a strain developed an extremely high-level of resistance to chloramphenicol, cross resistance to quinolones and erythromycin and displayed high levels of expression of the single component MFS transporter MdfA and multiple TolC-dependent transporters. The results suggest that the high versatility of the whole ensemble of transporters, the bacterial Effluxome, is an essential part of a strategy of survival in everchanging, at times noxious, environments. The concept of a functional Effluxome presents an alternative to the existing paradigms in the field and provides novel targets for the search for inhibitors of transporters as adjuvants of existing antibiotics.
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15
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Wu HH, Symersky J, Lu M. Structure of an engineered multidrug transporter MdfA reveals the molecular basis for substrate recognition. Commun Biol 2019; 2:210. [PMID: 31240248 PMCID: PMC6572762 DOI: 10.1038/s42003-019-0446-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Accepted: 04/30/2019] [Indexed: 02/05/2023] Open
Abstract
MdfA is a prototypical H+-coupled multidrug transporter that is characterized by extraordinarily broad substrate specificity. The involvement of specific H-bonds in MdfA-drug interactions and the simplicity of altering the substrate specificity of MdfA contradict the promiscuous nature of multidrug recognition, presenting a baffling conundrum. Here we show the X-ray structures of MdfA variant I239T/G354E in complexes with three electrically different ligands, determined at resolutions up to 2.2 Å. Our structures reveal that I239T/G354E interacts with these compounds differently from MdfA and that I239T/G354E possesses two discrete, non-overlapping substrate-binding sites. Our results shed new light on the molecular design of multidrug-binding and protonation sites and highlight the importance of often-neglected, long-range charge-charge interactions in multidrug recognition. Beyond helping to solve the ostensible conundrum of multidrug recognition, our findings suggest the mechanistic difference between substrate and inhibitor for any H+-dependent multidrug transporter, which may open new vistas on curtailing efflux-mediated multidrug resistance.
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Affiliation(s)
- Hsin-Hui Wu
- Department of Biochemistry and Molecular Biology, Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, IL 60064 USA
| | - Jindrich Symersky
- Department of Biochemistry and Molecular Biology, Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, IL 60064 USA
| | - Min Lu
- Department of Biochemistry and Molecular Biology, Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, IL 60064 USA
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16
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Abstract
The DEER (double electron-electron resonance, also called PELDOR) experiment, which probes the dipolar interaction between two spins and thus reveals distance information, is an important tool for structural studies. In recent years, shaped pump pulses have become a valuable addition to the DEER experiment. Shaped pulses offer an increased excitation bandwidth and the possibility to precisely adjust pulse parameters, which is beneficial especially for demanding biological samples. We have noticed that on our home built W-band spectrometer, the dead-time free 4-pulse DEER sequence with chirped pump pulses suffers from distortions at the end of the DEER trace. Although minor, these are crucial for Gd(III)-Gd(III) DEER where the modulation depth is on the order of a few percent. Here we present a modified DEER sequence—referred to as reversed DEER (rDEER)—that circumvents the coherence pathway which gives rise to the distortion. We compare the rDEER (with two chirped pump pulses) performance values to regular 4-pulse DEER with one monochromatic as well as two chirped pulses and investigate the source of the distortion. We demonstrate the applicability and effectivity of rDEER on three systems, ubiquitin labeled with Gd(III)-DOTA-maleimide (DOTA, 1,4,7,10-Tetraazacyclododecane-1,4,7,10-tetraacetic acid) or with Gd(III)-DO3A (DO3A, 1,4,7,10-Tetraazacyclododecane-1,4,7-triyl) triacetic acid) and the multidrug transporter MdfA, labeled with a Gd(III)-C2 tag, and report an increase in the signal-to-noise ratio in the range of 3 to 7 when comparing the rDEER with two chirped pump pulses to standard 4-pulse DEER.
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17
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Foong WE, Tam HK, Crames JJ, Averhoff B, Pos KM. The chloramphenicol/H+ antiporter CraA of Acinetobacter baumannii AYE reveals a broad substrate specificity. J Antimicrob Chemother 2019; 74:1192-1201. [DOI: 10.1093/jac/dkz024] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Revised: 11/23/2018] [Accepted: 01/08/2019] [Indexed: 12/15/2022] Open
Affiliation(s)
- Wuen Ee Foong
- Institute of Biochemistry, Goethe‐University Frankfurt, Max‐von‐Laue‐Str. 9, Frankfurt am Main, Germany
| | - Heng-Keat Tam
- Institute of Biochemistry, Goethe‐University Frankfurt, Max‐von‐Laue‐Str. 9, Frankfurt am Main, Germany
| | - Jan J Crames
- Institute of Biochemistry, Goethe‐University Frankfurt, Max‐von‐Laue‐Str. 9, Frankfurt am Main, Germany
| | - Beate Averhoff
- Department of Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Klaas M Pos
- Institute of Biochemistry, Goethe‐University Frankfurt, Max‐von‐Laue‐Str. 9, Frankfurt am Main, Germany
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18
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Nagarathinam K, Nakada-Nakura Y, Parthier C, Terada T, Juge N, Jaenecke F, Liu K, Hotta Y, Miyaji T, Omote H, Iwata S, Nomura N, Stubbs MT, Tanabe M. Outward open conformation of a Major Facilitator Superfamily multidrug/H + antiporter provides insights into switching mechanism. Nat Commun 2018; 9:4005. [PMID: 30275448 PMCID: PMC6167325 DOI: 10.1038/s41467-018-06306-x] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Accepted: 08/13/2018] [Indexed: 12/14/2022] Open
Abstract
Multidrug resistance (MDR) poses a major challenge to medicine. A principle cause of MDR is through active efflux by MDR transporters situated in the bacterial membrane. Here we present the crystal structure of the major facilitator superfamily (MFS) drug/H+ antiporter MdfA from Escherichia coli in an outward open conformation. Comparison with the inward facing (drug binding) state shows that, in addition to the expected change in relative orientations of the N- and C-terminal lobes of the antiporter, the conformation of TM5 is kinked and twisted. In vitro reconstitution experiments demonstrate the importance of selected residues for transport and molecular dynamics simulations are used to gain insights into antiporter switching. With the availability of structures of alternative conformational states, we anticipate that MdfA will serve as a model system for understanding drug efflux in MFS MDR antiporters. The multidrug resistance transporter mediated efflux of antibiotics from the bacterial cytoplasm represents a major challenge to medicine. Here authors solve the X-ray crystallographic structure of the drug/H+ antiporter MdfA from Escherichia coli and shed light on the conformational switching mechanism.
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Affiliation(s)
- Kumar Nagarathinam
- ZIK HALOmem, Kurt-Mothes-Straße 3, D-06120, Halle/Saale, Germany.,Institut für Biochemie und Biotechnologie, Charles-Tanford-Proteinzentrum, Martin-Luther Universität Halle-Wittenberg, Kurt-Mothes-Straße 3a, D-06120, Halle/Saale, Germany.,Institute of Virology, Hannover Medical School, Carl-Neuberg-Straße 1, D-30625, Hannover, Germany
| | - Yoshiko Nakada-Nakura
- Department of Cell Biology, Graduate School of Medicine, Kyoto University, Konoe-cho, Yoshida, Sakyo-ku, Kyoto, 606-8501, Japan
| | - Christoph Parthier
- Institut für Biochemie und Biotechnologie, Charles-Tanford-Proteinzentrum, Martin-Luther Universität Halle-Wittenberg, Kurt-Mothes-Straße 3a, D-06120, Halle/Saale, Germany
| | - Tohru Terada
- Agricultural Bioinformatics Research Unit, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan
| | - Narinobu Juge
- Advanced Science Research Center, Okayama University, 1-1-1 Kita-ku, Tsushima-naka, Okayama, 700-8530, Japan
| | - Frank Jaenecke
- ZIK HALOmem, Kurt-Mothes-Straße 3, D-06120, Halle/Saale, Germany
| | - Kehong Liu
- Department of Cell Biology, Graduate School of Medicine, Kyoto University, Konoe-cho, Yoshida, Sakyo-ku, Kyoto, 606-8501, Japan
| | - Yunhon Hotta
- Department of Cell Biology, Graduate School of Medicine, Kyoto University, Konoe-cho, Yoshida, Sakyo-ku, Kyoto, 606-8501, Japan
| | - Takaaki Miyaji
- Advanced Science Research Center, Okayama University, 1-1-1 Kita-ku, Tsushima-naka, Okayama, 700-8530, Japan
| | - Hiroshi Omote
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 1-1-1 Kita-ku, Tsushima-naka, Okayama, 700-8530, Japan
| | - So Iwata
- Department of Cell Biology, Graduate School of Medicine, Kyoto University, Konoe-cho, Yoshida, Sakyo-ku, Kyoto, 606-8501, Japan.,RIKEN, SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo, 679-5148, Japan
| | - Norimichi Nomura
- Department of Cell Biology, Graduate School of Medicine, Kyoto University, Konoe-cho, Yoshida, Sakyo-ku, Kyoto, 606-8501, Japan
| | - Milton T Stubbs
- ZIK HALOmem, Kurt-Mothes-Straße 3, D-06120, Halle/Saale, Germany. .,Institut für Biochemie und Biotechnologie, Charles-Tanford-Proteinzentrum, Martin-Luther Universität Halle-Wittenberg, Kurt-Mothes-Straße 3a, D-06120, Halle/Saale, Germany.
| | - Mikio Tanabe
- ZIK HALOmem, Kurt-Mothes-Straße 3, D-06120, Halle/Saale, Germany. .,Structural Biology Research Center, Institute of Materials Structure Science, KEK/High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki, 305-0801, Japan.
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19
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Bacterial efflux transporters in the limelight. Res Microbiol 2018; 169:349-350. [PMID: 30223033 DOI: 10.1016/j.resmic.2018.09.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Accepted: 09/05/2018] [Indexed: 11/20/2022]
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20
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Brochado AR, Telzerow A, Bobonis J, Banzhaf M, Mateus A, Selkrig J, Huth E, Bassler S, Zamarreño Beas J, Zietek M, Ng N, Foerster S, Ezraty B, Py B, Barras F, Savitski MM, Bork P, Göttig S, Typas A. Species-specific activity of antibacterial drug combinations. Nature 2018; 559:259-263. [PMID: 29973719 DOI: 10.1038/s41586-018-0278-9] [Citation(s) in RCA: 213] [Impact Index Per Article: 35.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Accepted: 05/24/2018] [Indexed: 12/12/2022]
Abstract
The spread of antimicrobial resistance has become a serious public health concern, making once-treatable diseases deadly again and undermining the achievements of modern medicine1,2. Drug combinations can help to fight multi-drug-resistant bacterial infections, yet they are largely unexplored and rarely used in clinics. Here we profile almost 3,000 dose-resolved combinations of antibiotics, human-targeted drugs and food additives in six strains from three Gram-negative pathogens-Escherichia coli, Salmonella enterica serovar Typhimurium and Pseudomonas aeruginosa-to identify general principles for antibacterial drug combinations and understand their potential. Despite the phylogenetic relatedness of the three species, more than 70% of the drug-drug interactions that we detected are species-specific and 20% display strain specificity, revealing a large potential for narrow-spectrum therapies. Overall, antagonisms are more common than synergies and occur almost exclusively between drugs that target different cellular processes, whereas synergies are more conserved and are enriched in drugs that target the same process. We provide mechanistic insights into this dichotomy and further dissect the interactions of the food additive vanillin. Finally, we demonstrate that several synergies are effective against multi-drug-resistant clinical isolates in vitro and during infections of the larvae of the greater wax moth Galleria mellonella, with one reverting resistance to the last-resort antibiotic colistin.
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Affiliation(s)
- Ana Rita Brochado
- European Molecular Biology Laboratory, Genome Biology Unit, Heidelberg, Germany
| | - Anja Telzerow
- European Molecular Biology Laboratory, Genome Biology Unit, Heidelberg, Germany
| | - Jacob Bobonis
- European Molecular Biology Laboratory, Genome Biology Unit, Heidelberg, Germany
| | - Manuel Banzhaf
- European Molecular Biology Laboratory, Genome Biology Unit, Heidelberg, Germany.,Institute of Microbiology & Infection, School of Biosciences, University of Birmingham, Birmingham, UK
| | - André Mateus
- European Molecular Biology Laboratory, Genome Biology Unit, Heidelberg, Germany
| | - Joel Selkrig
- European Molecular Biology Laboratory, Genome Biology Unit, Heidelberg, Germany
| | - Emily Huth
- Institute of Medical Microbiology and Infection Control, Hospital of Goethe University, Frankfurt am Main, Germany
| | - Stefan Bassler
- European Molecular Biology Laboratory, Genome Biology Unit, Heidelberg, Germany
| | - Jordi Zamarreño Beas
- Laboratoire de Chimie Bactérienne, Institut de Microbiologie de la Méditerranée, CNRS UMR 7283, Aix-Marseille Université, Marseille, France
| | - Matylda Zietek
- European Molecular Biology Laboratory, Genome Biology Unit, Heidelberg, Germany
| | - Natalie Ng
- Department of Bioengineering, Stanford University, Stanford, CA, USA
| | - Sunniva Foerster
- Institute of Social & Preventive Medicine, Institute of Infectious Diseases, University of Bern, Bern, Switzerland
| | - Benjamin Ezraty
- Laboratoire de Chimie Bactérienne, Institut de Microbiologie de la Méditerranée, CNRS UMR 7283, Aix-Marseille Université, Marseille, France
| | - Béatrice Py
- Laboratoire de Chimie Bactérienne, Institut de Microbiologie de la Méditerranée, CNRS UMR 7283, Aix-Marseille Université, Marseille, France
| | - Frédéric Barras
- Laboratoire de Chimie Bactérienne, Institut de Microbiologie de la Méditerranée, CNRS UMR 7283, Aix-Marseille Université, Marseille, France.,Institut Pasteur, Paris, France
| | - Mikhail M Savitski
- European Molecular Biology Laboratory, Genome Biology Unit, Heidelberg, Germany
| | - Peer Bork
- European Molecular Biology Laboratory, Structural & Computational Biology Unit, Heidelberg, Germany.,Max-Delbrück-Centre for Molecular Medicine, Berlin, Germany.,Molecular Medicine Partnership Unit, Heidelberg, Germany.,Department of Bioinformatics, Biocenter, University of Würzburg, Würzburg, Germany
| | - Stephan Göttig
- Institute of Medical Microbiology and Infection Control, Hospital of Goethe University, Frankfurt am Main, Germany
| | - Athanasios Typas
- European Molecular Biology Laboratory, Genome Biology Unit, Heidelberg, Germany. .,European Molecular Biology Laboratory, Structural & Computational Biology Unit, Heidelberg, Germany.
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21
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Trans-envelope multidrug efflux pumps of Gram-negative bacteria and their synergism with the outer membrane barrier. Res Microbiol 2018; 169:351-356. [PMID: 29454787 DOI: 10.1016/j.resmic.2018.02.002] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Revised: 02/05/2018] [Accepted: 02/06/2018] [Indexed: 11/20/2022]
Abstract
Antibiotic resistance is a serious threat to public health. Significant efforts are currently directed toward containment of the spread of resistance, finding new therapeutic options concerning resistant human and animal pathogens, and addressing the gaps in the fundamental understanding of mechanisms of resistance. Experimental data and kinetic modeling revealed a major factor in resistance, the synergy between active efflux and the low permeability barrier of the outer membrane, which dramatically reduces the intracellular accumulation of many antibiotics. The structural and mechanistic particularities of trans-envelope efflux pumps amplify the effectiveness of cell envelopes as permeability barriers. An important feature of this synergism is that efflux pumps and the outer membrane barriers are mechanistically independent and select antibiotics based on different physicochemical properties. The synergism amplifies even weak polyspecificity of multidrug efflux pumps and creates a major hurdle in the discovery and development of new therapeutics against Gram-negative pathogens.
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