1
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Gumbart JC, Ferreira JL, Hwang H, Hazel AJ, Cooper CJ, Parks JM, Smith JC, Zgurskaya HI, Beeby M. Lpp positions peptidoglycan at the AcrA-TolC interface in the AcrAB-TolC multidrug efflux pump. Biophys J 2021; 120:3973-3982. [PMID: 34411576 DOI: 10.1016/j.bpj.2021.08.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 07/02/2021] [Accepted: 08/11/2021] [Indexed: 01/07/2023] Open
Abstract
The multidrug efflux pumps of Gram-negative bacteria are a class of complexes that span the periplasm, coupling both the inner and outer membranes to expel toxic molecules. The best-characterized example of these tripartite pumps is the AcrAB-TolC complex of Escherichia coli. However, how the complex interacts with the peptidoglycan (PG) cell wall, which is anchored to the outer membrane (OM) by Braun's lipoprotein (Lpp), is still largely unknown. In this work, we present molecular dynamics simulations of a complete, atomistic model of the AcrAB-TolC complex with the inner membrane, OM, and PG layers all present. We find that the PG localizes to the junction of AcrA and TolC, in agreement with recent cryo-tomography data. Free-energy calculations reveal that the positioning of PG is determined by the length and conformation of multiple Lpp copies anchoring it to the OM. The distance between the PG and OM measured in cryo-electron microscopy images of wild-type E. coli also agrees with the simulation-derived spacing. Sequence analysis of AcrA suggests a conserved role for interactions with PG in the assembly and stabilization of efflux pumps, one that may extend to other trans-envelope complexes as well.
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Affiliation(s)
- James C Gumbart
- School of Physics, Georgia Institute of Technology, Atlanta, Georgia.
| | - Josie L Ferreira
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Hyea Hwang
- School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia
| | - Anthony J Hazel
- School of Physics, Georgia Institute of Technology, Atlanta, Georgia
| | - Connor J Cooper
- UT/ORNL Center for Molecular Biophysics, Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee
| | - Jerry M Parks
- UT/ORNL Center for Molecular Biophysics, Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee
| | - Jeremy C Smith
- UT/ORNL Center for Molecular Biophysics, Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee; Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee
| | - Helen I Zgurskaya
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma
| | - Morgan Beeby
- Department of Life Sciences, Imperial College London, London, United Kingdom
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2
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Rajapaksha P, Ojo I, Yang L, Pandeya A, Abeywansha T, Wei Y. Insight into the AcrAB-TolC Complex Assembly Process Learned from Competition Studies. Antibiotics (Basel) 2021; 10:antibiotics10070830. [PMID: 34356751 PMCID: PMC8300762 DOI: 10.3390/antibiotics10070830] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Revised: 06/30/2021] [Accepted: 07/06/2021] [Indexed: 11/16/2022] Open
Abstract
The RND family efflux pump AcrAB-TolC in E. coli and its homologs in other Gram-negative bacteria are major players in conferring multidrug resistance to the cells. While the structure of the pump complex has been elucidated with ever-increasing resolution through crystallography and Cryo-EM efforts, the dynamic assembly process remains poorly understood. Here, we tested the effect of overexpressing functionally defective pump components in wild type E. coli cells to probe the pump assembly process. Incorporation of a defective component is expected to reduce the efflux efficiency of the complex, leading to the so called "dominant negative" effect. Being one of the most intensively studied bacterial multidrug efflux pumps, many AcrA and AcrB mutations have been reported that disrupt efflux through different mechanisms. We examined five groups of AcrB and AcrA mutants, defective in different aspects of assembly and substrate efflux. We found that none of them demonstrated the expected dominant negative effect, even when expressed at concentrations many folds higher than their genomic counterpart. The assembly of the AcrAB-TolC complex appears to have a proof-read mechanism that effectively eliminated the formation of futile pump complex.
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3
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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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4
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Shvarev D, Maldener I. The HlyD-like membrane fusion protein All5304 is essential for acid stress survival of the filamentous cyanobacterium Anabaena sp. PCC 7120. FEMS Microbiol Lett 2020; 367:5863934. [PMID: 32592389 DOI: 10.1093/femsle/fnaa108] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Accepted: 06/25/2020] [Indexed: 12/23/2022] Open
Abstract
Acid stress is an environmental problem for plants and fresh water cyanobacteria like the filamentous, heterocyst forming species Anabaena sp. PCC 7120 (hereafter Anabaena sp.). Heterocyst differentiation, cell-cell communication and nitrogen fixation has been deeply studied in this model organism, but little is known about the cellular response of Anabaena sp. to decreased pH values, causing acid stress. ATP-binding cassette (ABC) transporters are involved in acid stress response in other bacteria, by exporting proteins responsible for survival under acidification. The genome of Anabaena sp. encodes numerous ABC transporter components, whose function is not known yet. Here, we describe the function of the gene all5304 encoding a protein with homology to membrane fusion proteins of tripartite efflux pumps driven by ABC transporters like HlyBD-TolC of Escherichia coli. The all5304 mutant shows less resistance against low pH, even though the expression of the gene is independent from the pH of the medium. We compared the exoproteome of the wild type and mutant cultures and identified three proteins-candidate substrates of the putative transporter. Including the in silico analysis of All5304, our results suggest that All5304 functions as part of an efflux pump, secreting of a protein necessary for acid tolerance in Anabaena sp.
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Affiliation(s)
- Dmitry Shvarev
- Organismic Interactions, Interfaculty Institute of Microbiology and Infection Medicine, Eberhard Karls University of Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany
| | - Iris Maldener
- Organismic Interactions, Interfaculty Institute of Microbiology and Infection Medicine, Eberhard Karls University of Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany
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5
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Zhang C, Dong S, Chen C, Zhang Q, Zhou D. Co-substrate addition accelerated amoxicillin degradation and detoxification by up-regulating degradation related enzymes and promoting cell resistance. JOURNAL OF HAZARDOUS MATERIALS 2020; 394:122574. [PMID: 32278124 DOI: 10.1016/j.jhazmat.2020.122574] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Revised: 03/06/2020] [Accepted: 03/20/2020] [Indexed: 06/11/2023]
Abstract
β-Lactam antibiotics are the most commonly used antibiotics, and are difficult to remove by conventional biological treatments because of their persistent and toxic nature. The addition of co-substrates has been successfully employed to improve the removal of refractory pollutants. So, we hypothesized that the co-substrate strategy would increase antibiotic degradation and benefit microbial survival. In this work, we reported that co-substrate (acetate) addition up-regulated key degrading enzymes and resistance related genes in a model bacteria strain (L. aquatilis) when being treated with 0.055 mM amoxicillin (AMO). β-Lactamase, amidases, transaminase, and amide C-N hydrolase showed increased activation. As a result, AMO removal reached ∼95 %, a ∼60 % increase over the control. Furthermore, the addition of acetate drove the down-stream TCA cycle, which accelerated the detoxification of the intermediates and reduced the microbial inhibition by the antibiotic products to as low as ∼15 %. Besides, the expression levels of genes encoding the efflux pump, penicillin binding proteins, and β-Lactamase were up-regulated, and the inhibition of peptidoglycan biosynthesis was down-regulated. The cell density was enhanced by ∼170 % and showed improved DNA replication. In conclusion, the addition of the co-substrate accelerated AMO degradation and detoxification by up-regulating degrading enzymes and promoting cell resistance.
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Affiliation(s)
- Chongjun Zhang
- Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun, 130021, China; Jilin Provincial Key Laboratory of Water Resources and Environment, Jilin University, Changchun, 130021, China; Engineering Lab for Water Pollution Control and Resources Recovery of Jilin Province, School of Environment, Northeast Normal University, Changchun, 130117, China
| | - Shuangshi Dong
- Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun, 130021, China; Jilin Provincial Key Laboratory of Water Resources and Environment, Jilin University, Changchun, 130021, China
| | - Congli Chen
- Engineering Lab for Water Pollution Control and Resources Recovery of Jilin Province, School of Environment, Northeast Normal University, Changchun, 130117, China
| | - Qifeng Zhang
- Engineering Lab for Water Pollution Control and Resources Recovery of Jilin Province, School of Environment, Northeast Normal University, Changchun, 130117, China
| | - Dandan Zhou
- Engineering Lab for Water Pollution Control and Resources Recovery of Jilin Province, School of Environment, Northeast Normal University, Changchun, 130117, China.
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6
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The coordinated action of RNase III and RNase G controls enolase expression in response to oxygen availability in Escherichia coli. Sci Rep 2019; 9:17257. [PMID: 31754158 PMCID: PMC6872547 DOI: 10.1038/s41598-019-53883-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Accepted: 10/09/2019] [Indexed: 01/25/2023] Open
Abstract
Rapid modulation of RNA function by endoribonucleases during physiological responses to environmental changes is known to be an effective bacterial biochemical adaptation. We report a molecular mechanism underlying the regulation of enolase (eno) expression by two endoribonucleases, RNase G and RNase III, the expression levels of which are modulated by oxygen availability in Escherichia coli. Analyses of transcriptional eno-cat fusion constructs strongly suggested the existence of cis-acting elements in the eno 5' untranslated region that respond to RNase III and RNase G cellular concentrations. Primer extension and S1 nuclease mapping analyses of eno mRNA in vivo identified three eno mRNA transcripts that are generated in a manner dependent on RNase III expression, one of which was found to accumulate in rng-deleted cells. Moreover, our data suggested that RNase III-mediated cleavage of primary eno mRNA transcripts enhanced Eno protein production, a process that involved putative cis-antisense RNA. We found that decreased RNase G protein abundance coincided with enhanced RNase III expression in E. coli grown anaerobically, leading to enhanced eno expression. Thereby, this posttranscriptional up-regulation of eno expression helps E. coli cells adjust their physiological reactions to oxygen-deficient metabolic modes. Our results revealed a molecular network of coordinated endoribonuclease activity that post-transcriptionally modulates the expression of Eno, a key enzyme in glycolysis.
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7
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Tsutsumi K, Yonehara R, Ishizaka-Ikeda E, Miyazaki N, Maeda S, Iwasaki K, Nakagawa A, Yamashita E. Structures of the wild-type MexAB-OprM tripartite pump reveal its complex formation and drug efflux mechanism. Nat Commun 2019; 10:1520. [PMID: 30944318 PMCID: PMC6447562 DOI: 10.1038/s41467-019-09463-9] [Citation(s) in RCA: 71] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Accepted: 03/11/2019] [Indexed: 11/30/2022] Open
Abstract
In Pseudomonas aeruginosa, MexAB–OprM plays a central role in multidrug resistance by ejecting various drug compounds, which is one of the causes of serious nosocomial infections. Although the structures of the components of MexAB–OprM have been solved individually by X-ray crystallography, no structural information for fully assembled pumps from P. aeruginosa were previously available. In this study, we present the structure of wild-type MexAB–OprM in the presence or absence of drugs at near-atomic resolution. The structure reveals that OprM does not interact with MexB directly, and that it opens its periplasmic gate by forming a complex. Furthermore, we confirm the residues essential for complex formation and observed a movement of the drug entrance gate. Based on these results, we propose mechanisms for complex formation and drug efflux. In Pseudomonas aeruginosa, MexAB–OprM plays a central role in multidrug resistance by ejecting various drug compounds. Here the authors present the structure of wild-type MexAB–OprM in the presence or absence of drugs and propose mechanisms for complex formation and drug efflux.
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Affiliation(s)
- Kenta Tsutsumi
- Institute for Protein Research, Osaka University, Suita, 565-0871, Osaka, Japan
| | - Ryo Yonehara
- Institute for Protein Research, Osaka University, Suita, 565-0871, Osaka, Japan
| | | | - Naoyuki Miyazaki
- Institute for Protein Research, Osaka University, Suita, 565-0871, Osaka, Japan
| | - Shintaro Maeda
- Institute for Protein Research, Osaka University, Suita, 565-0871, Osaka, Japan.,The Scripps Research Institute Department of Integrative Structural and Computational Biology, North Torrey Pines Road, La Jolla, CA, 10550, USA
| | - Kenji Iwasaki
- Institute for Protein Research, Osaka University, Suita, 565-0871, Osaka, Japan.,University of Tsukuba Life Science Center for Survival Dynamics, Tsukuba Advanced Research Alliance 1-1-1 Tennodai, Tsukuba, 305-8577, Ibaraki, Japan
| | - Atsushi Nakagawa
- Institute for Protein Research, Osaka University, Suita, 565-0871, Osaka, Japan
| | - Eiki Yamashita
- Institute for Protein Research, Osaka University, Suita, 565-0871, Osaka, Japan.
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8
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Jo I, Kim JS, Xu Y, Hyun J, Lee K, Ha NC. Recent paradigm shift in the assembly of bacterial tripartite efflux pumps and the type I secretion system. J Microbiol 2019; 57:185-194. [PMID: 30806976 DOI: 10.1007/s12275-019-8520-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2018] [Revised: 12/26/2018] [Accepted: 01/10/2019] [Indexed: 01/15/2023]
Abstract
Tripartite efflux pumps and the type I secretion system of Gram-negative bacteria are large protein complexes that span the entire cell envelope. These complexes expel antibiotics and other toxic substances or transport protein toxins from bacterial cells. Elucidating the binary and ternary complex structures at an atomic resolution are crucial to understanding the assembly and working mechanism. Recent advances in cryoelectron microscopy along with the construction of chimeric proteins drastically shifted the assembly models. In this review, we describe the current assembly models from a historical perspective and emphasize the common assembly mechanism for the assembly of diverse tripartite pumps and type I secretion systems.
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Affiliation(s)
- Inseong Jo
- Department of Agricultural Biotechnology, Center for Food Safety and Toxicology, Center for Food and Bioconvergence, Research Institute for Agriculture and Life Sciences, Seoul National University, Seoul, 08826, Republic of Korea
| | - Jin-Sik Kim
- Unit on Structural and Chemical Biology of Membrane Proteins, Cell Biology and Neurobiology Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Yongbin Xu
- Department of Bioengineering, College of Life Science, Dalian Minzu University, Dalian, Liaoning, 116600, P. R. China
| | - Jaekyung Hyun
- Electron Microscopy Research Center, Korea Basic Science Institute, Cheongju, 28119, Republic of Korea
| | - Kangseok Lee
- Department of Life Science, Chung-Ang University, Seoul, 06974, Republic of Korea
| | - Nam-Chul Ha
- Department of Agricultural Biotechnology, Center for Food Safety and Toxicology, Center for Food and Bioconvergence, Research Institute for Agriculture and Life Sciences, Seoul National University, Seoul, 08826, Republic of Korea.
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9
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Kanonenberg K, Spitz O, Erenburg IN, Beer T, Schmitt L. Type I secretion system—it takes three and a substrate. FEMS Microbiol Lett 2018; 365:4966979. [DOI: 10.1093/femsle/fny094] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Accepted: 04/09/2018] [Indexed: 12/20/2022] Open
Affiliation(s)
- Kerstin Kanonenberg
- Institute of Biochemistry, Heinrich Heine University, 40225 Düsseldorf, Germany
| | - Olivia Spitz
- Institute of Biochemistry, Heinrich Heine University, 40225 Düsseldorf, Germany
| | - Isabelle N Erenburg
- Institute of Biochemistry, Heinrich Heine University, 40225 Düsseldorf, Germany
| | - Tobias Beer
- Institute of Biochemistry, Heinrich Heine University, 40225 Düsseldorf, Germany
| | - Lutz Schmitt
- Institute of Biochemistry, Heinrich Heine University, 40225 Düsseldorf, Germany
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10
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Lu WJ, Lin HJ, Janganan TK, Li CY, Chin WC, Bavro VN, Lin HTV. ATP-Binding Cassette Transporter VcaM from Vibrio cholerae is Dependent on the Outer Membrane Factor Family for Its Function. Int J Mol Sci 2018; 19:ijms19041000. [PMID: 29584668 PMCID: PMC5979437 DOI: 10.3390/ijms19041000] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Revised: 03/23/2018] [Accepted: 03/25/2018] [Indexed: 11/16/2022] Open
Abstract
Vibrio cholerae ATP-binding cassette transporter VcaM (V. cholerae ABC multidrug resistance pump) has previously been shown to confer resistance to a variety of medically important drugs. In this study, we set to analyse its properties both in vitro in detergent-solubilised state and in vivo to differentiate its dependency on auxiliary proteins for its function. We report the first detailed kinetic parameters of purified VcaM and the rate of phosphate (Pi) production. To determine the possible functional dependencies of VcaM on the tripartite efflux pumps we then utilized different E. coli strains lacking the principal secondary transporter AcrB (Acriflavine resistance protein), as well as cells lacking the outer membrane factor (OMF) TolC (Tolerance to colicins). Consistent with the ATPase function of VcaM we found it to be susceptible to sodium orthovanadate (NaOV), however, we also found a clear dependency of VcaM function on TolC. Inhibitors targeting secondary active transporters had no effects on either VcaM-conferred resistance or Hoechst 33342 accumulation, suggesting that VcaM might be capable of engaging with the TolC-channel without periplasmic mediation by additional transporters. Our findings are indicative of VcaM being capable of a one-step substrate translocation from cytosol to extracellular space utilising the TolC-channel, making it the only multidrug ABC-transporter outside of the MacB-family with demonstrable TolC-dependency.
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Affiliation(s)
- Wen-Jung Lu
- Department of Food Science, National Taiwan Ocean University, No. 2, Pei-Ning Road, Keelung 202, Taiwan.
| | - Hsuan-Ju Lin
- Department of Food Science, National Taiwan Ocean University, No. 2, Pei-Ning Road, Keelung 202, Taiwan.
| | - Thamarai K Janganan
- School of Life Sciences, University of Bedfordshire, University Square, Luton LU1 3JU, UK.
| | - Cheng-Yi Li
- Department of Food Science, National Taiwan Ocean University, No. 2, Pei-Ning Road, Keelung 202, Taiwan.
| | - Wei-Chiang Chin
- Department of Food Science, National Taiwan Ocean University, No. 2, Pei-Ning Road, Keelung 202, Taiwan.
| | - Vassiliy N Bavro
- School of Biological Sciences, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, UK.
| | - Hong-Ting Victor Lin
- Department of Food Science, National Taiwan Ocean University, No. 2, Pei-Ning Road, Keelung 202, Taiwan.
- Center of Excellence for the Oceans, National Taiwan Ocean University, No. 2, Pei-Ning Road, Keelung 202, Taiwan.
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11
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Murata D, Okano H, Angkawidjaja C, Akutsu M, Tanaka SI, Kitahara K, Yoshizawa T, Matsumura H, Kado Y, Mizohata E, Inoue T, Sano S, Koga Y, Kanaya S, Takano K. Structural Basis for the Serratia marcescens Lipase Secretion System: Crystal Structures of the Membrane Fusion Protein and Nucleotide-Binding Domain. Biochemistry 2017; 56:6281-6291. [PMID: 29094929 DOI: 10.1021/acs.biochem.7b00985] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Serratia marcescens secretes a lipase, LipA, through a type I secretion system (T1SS). The T1SS for LipA, the Lip system, is composed of an inner membrane ABC transporter with its nucleotide-binding domains (NBD), LipB, a membrane fusion protein, LipC, and an outer membrane channel protein, LipD. Passenger protein secreted by this system has been functionally and structurally characterized well, but relatively little information about the transporter complex is available. Here, we report the crystallographic studies of LipC without the membrane anchor region, LipC-, and the NBD of LipB (LipB-NBD). LipC- crystallographic analysis has led to the determination of the structure of the long α-helical and lipoyl domains, but not the area where it interacts with LipB, suggesting that the region is flexible without LipB. The long α-helical domain has three α-helices, which interacts with LipD in the periplasm. LipB-NBD has the common overall architecture and ATP hydrolysis activity of ABC transporter NBDs. Using the predicted models of full-length LipB and LipD, the overall structural insight into the Lip system is discussed.
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Affiliation(s)
- Daichi Murata
- Department of Biomolecular Chemistry, Kyoto Prefectural University , Hangi-cho, Shimogamo, Sakyo-ku, Kyoto 606-8522, Japan
| | - Hiroyuki Okano
- Graduate School of Engineering, Osaka University , Yamadaoka, Suita 565-0871, Japan
| | - Clement Angkawidjaja
- Graduate School of Engineering, Osaka University , Yamadaoka, Suita 565-0871, Japan
| | - Masato Akutsu
- Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt , Max-von-Laue-Straße, 60438 Frankfurt am Main, Germany
| | - Shun-Ichi Tanaka
- College of Life Sciences, Ritsumeikan University , Noji-Higashi, Kusatsu 525-8577, Japan
| | - Kenyu Kitahara
- Department of Biomolecular Chemistry, Kyoto Prefectural University , Hangi-cho, Shimogamo, Sakyo-ku, Kyoto 606-8522, Japan
| | - Takuya Yoshizawa
- College of Life Sciences, Ritsumeikan University , Noji-Higashi, Kusatsu 525-8577, Japan
| | - Hiroyoshi Matsumura
- College of Life Sciences, Ritsumeikan University , Noji-Higashi, Kusatsu 525-8577, Japan
| | - Yuji Kado
- Graduate School of Engineering, Osaka University , Yamadaoka, Suita 565-0871, Japan
| | - Eiichi Mizohata
- Graduate School of Engineering, Osaka University , Yamadaoka, Suita 565-0871, Japan
| | - Tsuyoshi Inoue
- Graduate School of Engineering, Osaka University , Yamadaoka, Suita 565-0871, Japan
| | - Satoshi Sano
- Department of Biomolecular Chemistry, Kyoto Prefectural University , Hangi-cho, Shimogamo, Sakyo-ku, Kyoto 606-8522, Japan
| | - Yuichi Koga
- Graduate School of Engineering, Osaka University , Yamadaoka, Suita 565-0871, Japan
| | - Shigenori Kanaya
- Graduate School of Engineering, Osaka University , Yamadaoka, Suita 565-0871, Japan
| | - Kazufumi Takano
- Department of Biomolecular Chemistry, Kyoto Prefectural University , Hangi-cho, Shimogamo, Sakyo-ku, Kyoto 606-8522, Japan
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12
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Opening the Channel: the Two Functional Interfaces of Pseudomonas aeruginosa OpmH with the Triclosan Efflux Pump TriABC. J Bacteriol 2016; 198:3176-3185. [PMID: 27645384 DOI: 10.1128/jb.00535-16] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2016] [Accepted: 09/08/2016] [Indexed: 12/11/2022] Open
Abstract
TriABC-OpmH is an efflux pump from Pseudomonas aeruginosa with an unusual substrate specificity and protein composition. When overexpressed, this pump confers a high level of resistance to the biocide triclosan and the detergent SDS, which are commonly used in combinations for antimicrobial treatments. This activity requires an RND transporter (TriC), an outer membrane channel (OpmH), and two periplasmic membrane fusion proteins (TriA and TriB) with nonequivalent functions. In the active complex, TriA is responsible for the recruitment of OpmH, while TriB is responsible for stimulation of the transporter TriC. Here, we used the functional and structural differences between the two membrane fusion proteins to link their functional roles to specific interactions with OpmH. Our results provide evidence that the TriB-dependent stimulation of the TriC transporter is coupled to opening of the OpmH aperture through binding to the interprotomer groove of OpmH. IMPORTANCE Multidrug efflux transporters are important contributors to intrinsic and acquired antibiotic resistance in clinics. In Gram-negative bacteria, these transporters have a characteristic tripartite architecture spanning the entire two-membrane cell envelope. How such complexes are assembled and how the reactions separated in two different membranes are coupled to provide efficient efflux of various compounds across the cell envelope remain unclear. This study addressed these questions, and the results suggest a mechanism for functional integration of drug efflux by the inner membrane transporter and opening of the channel for transport across the outer membrane.
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13
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Kim JS, Song S, Lee M, Lee S, Lee K, Ha NC. Crystal Structure of a Soluble Fragment of the Membrane Fusion Protein HlyD in a Type I Secretion System of Gram-Negative Bacteria. Structure 2016; 24:477-85. [DOI: 10.1016/j.str.2015.12.012] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Revised: 12/15/2015] [Accepted: 12/16/2015] [Indexed: 10/22/2022]
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14
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Jeong H, Kim JS, Song S, Shigematsu H, Yokoyama T, Hyun J, Ha NC. Pseudoatomic Structure of the Tripartite Multidrug Efflux Pump AcrAB-TolC Reveals the Intermeshing Cogwheel-like Interaction between AcrA and TolC. Structure 2016; 24:272-6. [PMID: 26777412 DOI: 10.1016/j.str.2015.12.007] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Revised: 11/05/2015] [Accepted: 12/08/2015] [Indexed: 10/22/2022]
Abstract
The resistance-nodulation-division type tripartite pump AcrAB-TolC and its homologs are responsible for multidrug resistance in Gram-negative bacteria by expelling a wide variety of toxic substrates. The three essential components, AcrA, AcrB, and TolC, must function in concert with each respective binding partner within the complex. In this study, we report an 8.2-Å resolution cryo-electron microscopy (cryo-EM) 3D reconstruction of the complex that consists of an AcrAB fusion protein and a chimeric TolC protein. The pseudoatomic structure derived from the cryo-EM reconstruction clearly demonstrates a model only compatible with the adaptor bridging mechanism, wherein the funnel-like AcrA hexamer forms an intermeshing cogwheel-like interaction with the α-barrel tip region of TolC. These observations provide a structural milestone for understanding multidrug resistance in pathogenic Gram-negative bacteria, and may also lead to the design of new antibacterial drugs.
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Affiliation(s)
- Hyeongseop Jeong
- Nano-Bio Electron Microscopy Research Team, Korea Basic Science Institute, Daejeon 305-806, Republic of Korea
| | - Jin-Sik Kim
- Department of Agricultural Biotechnology, Center for Food and Bioconvergence, Center for Food Safety and Toxicology, Research Institute for Agricultural and Life Sciences, Seoul National University, Seoul 151-921, Republic of Korea
| | - Saemee Song
- Department of Agricultural Biotechnology, Center for Food and Bioconvergence, Center for Food Safety and Toxicology, Research Institute for Agricultural and Life Sciences, Seoul National University, Seoul 151-921, Republic of Korea
| | - Hideki Shigematsu
- Division of Structural and Synthetic Biology, RIKEN Center for Life Science Technologies, Yokohama, Kanagawa 230-0045, Japan
| | - Takeshi Yokoyama
- Division of Structural and Synthetic Biology, RIKEN Center for Life Science Technologies, Yokohama, Kanagawa 230-0045, Japan
| | - Jaekyung Hyun
- Nano-Bio Electron Microscopy Research Team, Korea Basic Science Institute, Daejeon 305-806, Republic of Korea.
| | - Nam-Chul Ha
- Department of Agricultural Biotechnology, Center for Food and Bioconvergence, Center for Food Safety and Toxicology, Research Institute for Agricultural and Life Sciences, Seoul National University, Seoul 151-921, Republic of Korea.
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15
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Weeks JW, Nickels LM, Ntreh AT, Zgurskaya HI. Non-equivalent roles of two periplasmic subunits in the function and assembly of triclosan pump TriABC from Pseudomonas aeruginosa. Mol Microbiol 2015; 98:343-56. [PMID: 26193906 DOI: 10.1111/mmi.13124] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/07/2015] [Indexed: 11/27/2022]
Abstract
In Gram-negative bacteria, multidrug efflux transporters function in complexes with periplasmic membrane fusion proteins (MFPs) that enable antibiotic efflux across the outer membrane. In this study, we analyzed the function, composition and assembly of the triclosan efflux transporter TriABC-OpmH from Pseudomonas aeruginosa. We report that this transporter possesses a surprising substrate specificity that encompasses not only triclosan but the detergent SDS, which are often used together in antibacterial soaps. These two compounds interact antagonistically in a TriABC-dependent manner and negate antibacterial properties of each other. Unlike other efflux pumps that rely on a single MFP for their activities, two different MFPs, TriA and TriB, are required for triclosan/SDS resistance mediated by TriABC-OpmH. We found that analogous mutations in the α-helical hairpin and membrane proximal domains of TriA and TriB differentially affect triclosan efflux and assembly of the complex. Furthermore, our results show that TriA and TriB function as a dimer, in which TriA is primarily responsible for stabilizing interactions with the outer membrane channel, whereas TriB is important for the stimulation of the transporter. We conclude that MFPs are engaged into complexes as asymmetric dimers, in which each protomer plays a specific role.
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Affiliation(s)
- Jon W Weeks
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, OK, 73019, USA
| | - Logan M Nickels
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, OK, 73019, USA
| | - Abigail T Ntreh
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, OK, 73019, USA
| | - Helen I Zgurskaya
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, OK, 73019, USA
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16
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Du D, van Veen HW, Murakami S, Pos KM, Luisi BF. Structure, mechanism and cooperation of bacterial multidrug transporters. Curr Opin Struct Biol 2015; 33:76-91. [PMID: 26282926 DOI: 10.1016/j.sbi.2015.07.015] [Citation(s) in RCA: 106] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Revised: 06/29/2015] [Accepted: 07/24/2015] [Indexed: 12/13/2022]
Abstract
Cells from all domains of life encode energy-dependent trans-membrane transporters that can expel harmful substances including clinically applied therapeutic agents. As a collective body, these transporters perform as a super-system that confers tolerance to an enormous range of harmful compounds and consequently aid survival in hazardous environments. In the Gram-negative bacteria, some of these transporters serve as energy-transducing components of tripartite assemblies that actively efflux drugs and other harmful compounds, as well as deliver virulence agents across the entire cell envelope. We draw together recent structural and functional data to present the current models for the transport mechanisms for the main classes of multi-drug transporters and their higher-order assemblies.
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Affiliation(s)
- Dijun Du
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, UK
| | - Hendrik W van Veen
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
| | - Satoshi Murakami
- Division of Structure and Function of Biomolecules, Department of Life Science, Tokyo Institute of Technology, Yokohama 226-8503, Japan
| | - Klaas M Pos
- Institute of Biochemistry, Goethe Universität Frankfurt, Max-von-Laue-Straße 9, D-60438 Frankfurt, Germany
| | - Ben F Luisi
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, UK.
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17
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Anes J, McCusker MP, Fanning S, Martins M. The ins and outs of RND efflux pumps in Escherichia coli. Front Microbiol 2015; 6:587. [PMID: 26113845 PMCID: PMC4462101 DOI: 10.3389/fmicb.2015.00587] [Citation(s) in RCA: 162] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2015] [Accepted: 05/28/2015] [Indexed: 11/13/2022] Open
Abstract
Infectious diseases remain one of the principal causes of morbidity and mortality in the world. Relevant authorities including the WHO and CDC have expressed serious concern regarding the continued increase in the development of multidrug resistance among bacteria. They have also reaffirmed the urgent need for investment in the discovery and development of new antibiotics and therapeutic approaches to treat multidrug resistant (MDR) bacteria. The extensive use of antimicrobial compounds in diverse environments, including farming and healthcare, has been identified as one of the main causes for the emergence of MDR bacteria. Induced selective pressure has led bacteria to develop new strategies of defense against these chemicals. Bacteria can accomplish this by several mechanisms, including enzymatic inactivation of the target compound; decreased cell permeability; target protection and/or overproduction; altered target site/enzyme and increased efflux due to over-expression of efflux pumps. Efflux pumps can be specific for a single substrate or can confer resistance to multiple antimicrobials by facilitating the extrusion of a broad range of compounds including antibiotics, heavy metals, biocides and others, from the bacterial cell. To overcome antimicrobial resistance caused by active efflux, efforts are required to better understand the fundamentals of drug efflux mechanisms. There is also a need to elucidate how these mechanisms are regulated and how they respond upon exposure to antimicrobials. Understanding these will allow the development of combined therapies using efflux inhibitors together with antibiotics to act on Gram-negative bacteria, such as the emerging globally disseminated MDR pathogen Escherichia coli ST131 (O25:H4). This review will summarize the current knowledge on resistance-nodulation-cell division efflux mechanisms in E. coli, a bacteria responsible for community and hospital-acquired infections, as well as foodborne outbreaks worldwide.
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Affiliation(s)
- João Anes
- UCD Centre for Food Safety, School of Public Health, Physiotherapy and Population Science, UCD Centre for Molecular Innovation and Drug Discovery, University College Dublin Dublin, Ireland
| | - Matthew P McCusker
- UCD Centre for Food Safety, School of Public Health, Physiotherapy and Population Science, UCD Centre for Molecular Innovation and Drug Discovery, University College Dublin Dublin, Ireland
| | - Séamus Fanning
- UCD Centre for Food Safety, School of Public Health, Physiotherapy and Population Science, UCD Centre for Molecular Innovation and Drug Discovery, University College Dublin Dublin, Ireland
| | - Marta Martins
- UCD Centre for Food Safety, School of Public Health, Physiotherapy and Population Science, UCD Centre for Molecular Innovation and Drug Discovery, University College Dublin Dublin, Ireland
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18
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Molecular architecture of the bacterial tripartite multidrug efflux pump focusing on the adaptor bridging model. J Microbiol 2015; 53:355-64. [DOI: 10.1007/s12275-015-5248-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Revised: 05/18/2015] [Accepted: 05/18/2015] [Indexed: 10/23/2022]
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19
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Symmons MF, Marshall RL, Bavro VN. Architecture and roles of periplasmic adaptor proteins in tripartite efflux assemblies. Front Microbiol 2015; 6:513. [PMID: 26074901 PMCID: PMC4446572 DOI: 10.3389/fmicb.2015.00513] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Accepted: 05/08/2015] [Indexed: 12/12/2022] Open
Abstract
Recent years have seen major advances in the structural understanding of the different components of tripartite efflux assemblies, which encompass the multidrug efflux (MDR) pumps and type I secretion systems. The majority of these investigations have focused on the role played by the inner membrane transporters and the outer membrane factor (OMF), leaving the third component of the system – the Periplasmic Adaptor Proteins (PAPs) – relatively understudied. Here we review the current state of knowledge of these versatile proteins which, far from being passive linkers between the OMF and the transporter, emerge as active architects of tripartite assemblies, and play diverse roles in the transport process. Recognition between the PAPs and OMFs is essential for pump assembly and function, and targeting this interaction may provide a novel avenue for combating multidrug resistance. With the recent advances elucidating the drug efflux and energetics of the tripartite assemblies, the understanding of the interaction between the OMFs and PAPs is the last piece remaining in the complete structure of the tripartite pump assembly puzzle.
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Affiliation(s)
- Martyn F Symmons
- Department of Veterinary Medicine, University of Cambridge Cambridge, UK
| | - Robert L Marshall
- Institute of Microbiology and Infection, University of Birmingham Birmingham, UK
| | - Vassiliy N Bavro
- Institute of Microbiology and Infection, University of Birmingham Birmingham, UK
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20
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Functional analysis of Vibrio vulnificus RND efflux pumps homologous to Vibrio cholerae VexAB and VexCD, and to Escherichia coli AcrAB. J Microbiol 2015; 53:256-61. [PMID: 25740377 DOI: 10.1007/s12275-015-5037-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Revised: 01/28/2015] [Accepted: 01/29/2015] [Indexed: 01/05/2023]
Abstract
Resistance-nodulation-division (RND) efflux pumps are associated with multidrug resistance in many gram-negative pathogens. The genome of Vibrio vulnificus encodes 11 putative RND pumps homologous to those of Vibrio cholerae and Escherichia coli. In this study, we analyzed three putative RND efflux pumps, showing homology to V. cholerae VexAB and VexCD and to E. coli AcrAB, for their functional roles in multidrug resistance of V. vulnificus. Deletion of the vexAB homolog resulted in increased susceptibility of V. vulnificus to bile acid, acriflavine, ethidium bromide, and erythromycin, whereas deletion of acrAB homologs rendered V. vulnificus more susceptible to acriflavine only. Deletion of vexCD had no effect on susceptibility of V. vulnificus to these chemicals. Upon exposure to these antibacterial chemicals, expression of tolCV1 and tolCV2, which are putative outer membrane factors of RND efflux pumps, was induced, whereas expression levels of vexAB, vexCD, and acrAB homologs were not significantly changed. Our results show that the V. vulnificus homologs of VexAB largely contributed to in vitro antimicrobial resistance with a broad substrate specificity that was partially redundant with the AcrAB pump homologs.
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21
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Du D, van Veen HW, Luisi BF. Assembly and operation of bacterial tripartite multidrug efflux pumps. Trends Microbiol 2015; 23:311-9. [PMID: 25728476 DOI: 10.1016/j.tim.2015.01.010] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Revised: 01/13/2015] [Accepted: 01/22/2015] [Indexed: 01/21/2023]
Abstract
Microorganisms encode several classes of transmembrane pumps that can expel an enormous range of toxic substances, thereby improving their fitness in harsh environments and contributing to resistance against antimicrobial agents. In Gram-negative bacteria these pumps can take the form of tripartite assemblies that actively efflux drugs and other harmful compounds across the cell envelope. We describe recent structural and functional data that have provided insights into the transport mechanisms of these intricate molecular machines.
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Affiliation(s)
- Dijun Du
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, UK
| | - Hendrik W van Veen
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
| | - Ben F Luisi
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, UK.
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22
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Kim JS, Jeong H, Song S, Kim HY, Lee K, Hyun J, Ha NC. Structure of the tripartite multidrug efflux pump AcrAB-TolC suggests an alternative assembly mode. Mol Cells 2015; 38:180-6. [PMID: 26013259 PMCID: PMC4332038 DOI: 10.14348/molcells.2015.2277] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2014] [Revised: 11/17/2014] [Accepted: 11/18/2014] [Indexed: 11/27/2022] Open
Abstract
Escherichia coli AcrAB-TolC is a multidrug efflux pump that expels a wide range of toxic substrates. The dynamic nature of the binding or low affinity between the components has impeded elucidation of how the three components assemble in the functional state. Here, we created fusion proteins composed of AcrB, a transmembrane linker, and two copies of AcrA. The fusion protein exhibited acridine pumping activity, suggesting that the protein reflects the functional structure in vivo. To discern the assembling mode with TolC, the AcrBA fusion protein was incubated with TolC or a chimeric protein containing the TolC aperture tip region. Three-dimensional structures of the complex proteins were determined through transmission electron microscopy. The overall structure exemplifies the adaptor bridging model, wherein the funnel-like AcrA hexamer forms an intermeshing cogwheel interaction with the α-barrel tip region of TolC, and a direct interaction between AcrB and TolC is not allowed. These observations provide a structural blueprint for understanding multidrug resistance in pathogenic Gram-negative bacteria.
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Affiliation(s)
- Jin-Sik Kim
- Department of Manufacturing Pharmacy, Pusan National University, Busan 609-735, Korea
| | - Hyeongseop Jeong
- Division of Electron Microscopic Research, Korea Basic Science Institute, Dajeon 169-148, Korea
| | - Saemee Song
- Department of Food and Animal Biotechnology, Department of Agricultural Biotechnology, Center for Food and Bioconvergence, Research Institute for Agricultural and Life Sciences, Seoul National University, Seoul 151-742, Korea
- Department of Life Science, Chung-Ang University, Seoul 156-756, Korea
| | - Hye-Yeon Kim
- Division of Magnetic Resonance, Korea Basic Science Institute, Chungbuk 363-883, Korea
| | - Kangseok Lee
- Department of Life Science, Chung-Ang University, Seoul 156-756, Korea
| | - Jaekyung Hyun
- Division of Electron Microscopic Research, Korea Basic Science Institute, Dajeon 169-148, Korea
| | - Nam-Chul Ha
- Department of Food and Animal Biotechnology, Department of Agricultural Biotechnology, Center for Food and Bioconvergence, Research Institute for Agricultural and Life Sciences, Seoul National University, Seoul 151-742, Korea
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23
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Song S, Hwang S, Lee S, Ha NC, Lee K. Interaction mediated by the putative tip regions of MdsA and MdsC in the formation of a Salmonella-specific tripartite efflux pump. PLoS One 2014; 9:e100881. [PMID: 24960027 PMCID: PMC4069162 DOI: 10.1371/journal.pone.0100881] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2014] [Accepted: 05/31/2014] [Indexed: 01/12/2023] Open
Abstract
To survive in the presence of a wide range of toxic compounds, gram-negative bacteria expel such compounds via tripartite efflux pumps that span both the inner and outer membranes. The Salmonella-specific MdsAB pump consists of MdsB, a resistance-nodulation-division (RND)-type inner membrane transporter (IMT) that requires the membrane fusion protein (MFP) MdsA, and an outer membrane protein (OMP; MdsC or TolC) to form a tripartite efflux complex. In this study, we investigated the role of the putative tip regions of MdsA and its OMPs, MdsC and TolC, in the formation of a functional MdsAB-mediated efflux pump. Comparative analysis indicated that although sequence homologies of MdsA and MdsC with other MFPs and OMPs, respectively, are extremely low, key residues in the putative tip regions of these proteins are well conserved. Mutagenesis studies on these conserved sites demonstrated their importance for the physical and functional interactions required to form an MdsAB-mediated pump. Our studies suggest that, despite differences in the primary amino acid sequences and functions of various OMPs and MFPs, interactions mediated by the conserved tip regions of OMP and MFP are required for the formation of functional tripartite efflux pumps in gram-negative bacteria.
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Affiliation(s)
- Saemee Song
- Department of Life Science, Chung-Ang University, Seoul, Republic of Korea
| | - Soonhye Hwang
- Department of Life Science, Chung-Ang University, Seoul, Republic of Korea
| | - Seunghwa Lee
- Department of Life Science, Chung-Ang University, Seoul, Republic of Korea
| | - Nam-Chul Ha
- Department of Food and Animal Biotechnology, Department of Agricultural Biotechnology, Research Institute for Agriculture and Life Sciences, Seoul National University, Seoul, Republic of Korea
- * E-mail: (NCH); (KL)
| | - Kangseok Lee
- Department of Life Science, Chung-Ang University, Seoul, Republic of Korea
- * E-mail: (NCH); (KL)
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24
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Functional analysis of TolC homologs in Vibrio vulnificus. Curr Microbiol 2014; 68:729-34. [PMID: 24515351 DOI: 10.1007/s00284-014-0537-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Accepted: 12/18/2013] [Indexed: 12/15/2022]
Abstract
Gram-negative bacteria use tripartite pumps to transport antibacterial drugs and other toxic compounds across the inner and outer membranes, which are separated by the periplasmic space. The TolC protein is an outer membrane factor that participates in the formation of tripartite efflux pumps. The genome of Vibrio vulnificus encodes two E. coli TolC homologs, TolCV1 and TolCV2. Here, we show that both TolCV1 and TolCV2 are involved in the efflux of antimicrobial agents. Deletion of tolCV1 resulted in increased susceptibility of V. vulnificus to chemical detergents, DNA intercalating agents, and antibiotics including erythromycin, novobiocin, and tetracycline, whereas deletion of tolCV2 rendered V. vulnificus more susceptible to the above mentioned antibiotics only. We also observed that tolCV1 deletion resulted in reduced motility of V. vulnificus. Our results indicate active roles for TolCV1 and TolCV2 in the physiology of V. vulnificus.
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25
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Lee S, Song S, Lee M, Hwang S, Kim JS, Ha NC, Lee K. Interaction between the α-barrel tip of Vibrio vulnificus TolC homologs and AcrA implies the adapter bridging model. J Microbiol 2014; 52:148-53. [PMID: 24500479 DOI: 10.1007/s12275-014-3578-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2013] [Revised: 12/05/2013] [Accepted: 12/06/2013] [Indexed: 10/25/2022]
Abstract
The AcrAB-TolC multidrug efflux pump confers resistance to Escherichia coli against many antibiotics and toxic compounds. The TolC protein is an outer membrane factor that participates in the formation of type I secretion systems. The genome of Vibrio vulnificus encodes two proteins homologous to the E. coli TolC, designated TolCV1 and TolCV2. Here, we show that both TolCV1 and TolCV2 partially complement the E. coli TolC function and physically interact with the membrane fusion protein AcrA, a component of the E. coli AcrAB-TolC efflux pump. Using site-directed mutational analyses and an in vivo cross-linking assay, we demonstrated that the α-barrel tip region of TolC homologs plays a critical role in the formation of functional AcrAB-TolC efflux pumps. Our findings suggest the adapter bridging model as a general assembly mechanism for tripartite drug efflux pumps in Gram-negative bacteria.
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Affiliation(s)
- Seunghwa Lee
- Department of Life Science, Chung-Ang University, Seoul, 156-756, Republic of Korea
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26
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Weeks JW, Bavro VN, Misra R. Genetic assessment of the role of AcrB β-hairpins in the assembly of the TolC-AcrAB multidrug efflux pump of Escherichia coli. Mol Microbiol 2014; 91:965-75. [PMID: 24386963 DOI: 10.1111/mmi.12508] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/02/2014] [Indexed: 01/08/2023]
Abstract
The tripartite AcrAB-TolC multidrug efflux pump of Escherichia coli is the central conduit for cell-toxic compounds and contributes to antibiotic resistance. While high-resolution structures of all three proteins have been solved, much remains to be learned as to how the individual components come together to form a functional complex. In this study, we investigated the importance of the AcrB β-hairpins belonging to the DN and DC subdomains, which are presumed to dock with TolC, in complex stability and activity of the complete pump. Our data show that the DN subdomain β-hairpin residues play a more critical role in complex stability and activity than the DC subdomain hairpin residues. The failure of the AcrB DN β-hairpin deletion mutant to engage with TolC leads to the drug hypersensitivity phenotype, which is reversed by compensatory alterations in the lipoyl and β-barrel domains of AcrA. Moreover, AcrA and TolC mutants that induce TolC opening also reverse the drug hypersensitivity phenotype of the AcrB β-hairpin mutants, indicating a failure by the AcrB mutant to interact and thus induce TolC opening on its own. Together, these data suggest that both AcrB β-hairpins and AcrA act to stabilize the tripartite complex and induce TolC opening for drug expulsion.
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Affiliation(s)
- Jon W Weeks
- School of Life Sciences, Arizona State University, Tempe, AZ, 85287, USA; Department of Chemistry and Biochemistry, The University of Oklahoma, Norman, OK, 73019, USA
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27
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Molecular basis of active copper resistance mechanisms in Gram-negative bacteria. Cell Biol Toxicol 2013; 29:397-405. [PMID: 24072389 PMCID: PMC3847284 DOI: 10.1007/s10565-013-9262-1] [Citation(s) in RCA: 118] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2013] [Accepted: 09/16/2013] [Indexed: 10/26/2022]
Abstract
Copper is a metallic element that is crucial for cell metabolism; however, in extended concentrations, it is toxic for all living organisms. The dual nature of copper has forced organisms, including bacteria, to keep a tight hold on cellular copper content. This challenge has led to the evolution of complex mechanisms that on one hand enable them to deliver the essential element and on the other to protect cells against its toxicity. Such mechanisms have been found in both eukaryotic and prokaryotic cells. In bacteria a number of different systems such as extra- and intracellular sequestration, enzymatic detoxification, and metal removal from the cell enabling them to survive in the presence of high concentration of copper have been identified. Gram-negative bacteria, due to their additional compartment, need to deal with both cytoplasmic and periplasmic copper. Therefore, these bacteria have evolved intricate and precisely regulated systems which interact with each other. In this review the active mechanisms of copper resistance at their molecular level are discussed.
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28
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Gonzales L, Ali ZB, Nygren E, Wang Z, Karlsson S, Zhu B, Quiding-Järbrink M, Sjöling Å. Alkaline pH Is a signal for optimal production and secretion of the heat labile toxin, LT in enterotoxigenic Escherichia coli (ETEC). PLoS One 2013; 8:e74069. [PMID: 24058516 PMCID: PMC3776858 DOI: 10.1371/journal.pone.0074069] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Accepted: 07/26/2013] [Indexed: 01/12/2023] Open
Abstract
Enterotoxigenic Escherichia coli (ETEC) cause secretory diarrhea in children and travelers to endemic areas. ETEC spreads through the fecal-oral route. After ingestion, ETEC passes through the stomach and duodenum before it colonizes the lower part of the small intestine, exposing bacteria to a wide range of pH and environmental conditions. This study aimed to determine the impact of external pH and activity of the Cyclic AMP receptor protein (CRP) on the regulation of production and secretion of heat labile (LT) enterotoxin. ETEC strain E2863wt and its isogenic mutant E2863ΔCRP were grown in LBK media buffered to pH 5, 7 and 9. GM1 ELISA, cDNA and cAMP analyses were carried out on bacterial pellet and supernatant samples derived from 3 and 5 hours growth and from overnight cultures. We confirm that CRP is a repressor of LT transcription and production as has been shown before but we show for the first time that CRP is a positive regulator of LT secretion both in vitro and in vivo. LT secretion increased at neutral to alkaline pH compared to acidic pH 5 where secretion was completely inhibited. At pH 9 secretion of LT was optimal resulting in 600 percent increase of secreted LT compared to unbuffered LBK media. This effect was not due to membrane leakage since the bacteria were viable at pH 9. The results indicate that the transition to the alkaline duodenum and/or exposure to high pH close to the epithelium as well as activation of the global transcription factor CRP are signals that induce secretion of the LT toxin in ETEC.
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Affiliation(s)
- Lucia Gonzales
- Department of Microbiology and Immunology, Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden
- Instituto de Biología Molecular y Biotecnología, Universidad Mayor de San Andrés, La Paz, Bolivia
| | - Zahra Bagher Ali
- Department of Microbiology and Immunology, Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden
| | - Erik Nygren
- Department of Microbiology and Immunology, Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden
| | - Zhiyun Wang
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, PR China
| | - Stefan Karlsson
- Department of Microbiology and Immunology, Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden
| | - Baoli Zhu
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, PR China
| | - Marianne Quiding-Järbrink
- Department of Microbiology and Immunology, Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden
| | - Åsa Sjöling
- Department of Microbiology and Immunology, Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden
- * E-mail:
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29
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The α-barrel tip region of Escherichia coli TolC homologs of Vibrio vulnificus interacts with the MacA protein to form the functional macrolide-specific efflux pump MacAB-TolC. J Microbiol 2013; 51:154-9. [PMID: 23625214 DOI: 10.1007/s12275-013-2699-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Accepted: 12/25/2012] [Indexed: 10/26/2022]
Abstract
TolC and its homologous family of proteins are outer membrane factors that are essential for exporting small molecules and toxins across the outer membrane in Gram-negative bacteria. Two open reading frames in the Vibrio vulnificus genome that encode proteins homologous to Escherichia coli TolC, designated TolCV1 and TolCV2, have 51.3% and 29.6% amino acid identity to TolC, respectively. In this study, we show that TolCV1 and TolCV2 functionally and physically interacted with the membrane fusion protein, MacA, a component of the macrolide-specific MacAB-TolC pump of E. coli. We further show that the conserved residues located at the aperture tip region of the α-hairpin of TolCV1 and TolCV2 played an essential role in the formation of the functional MacAB-TolC pump using site-directed mutational analyses. Our findings suggest that these outer membrane factors have conserved tip-to-tip interaction with the MacA membrane fusion protein for action of the drug efflux pump in Gram-negative bacteria.
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30
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Masi M, Pagès JM. Structure, Function and Regulation of Outer Membrane Proteins Involved in Drug Transport in Enterobactericeae: the OmpF/C - TolC Case. Open Microbiol J 2013; 7:22-33. [PMID: 23569467 PMCID: PMC3617542 DOI: 10.2174/1874285801307010022] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2012] [Revised: 02/01/2013] [Accepted: 02/03/2013] [Indexed: 11/26/2022] Open
Abstract
Antibiotic translocation across membranes of Gram-negative bacteria is a key step for the activity on their specific intracellular targets. Resistant bacteria control their membrane permeability as a first line of defense to protect themselves against external toxic compounds such as antibiotics and biocides. On one hand, resistance to small hydrophilic antibiotics such as ß-lactams and fluoroquinolones frequently results from the « closing » of their way in: the general outer membrane porins. On the other hand, an effective way out for a wide range of antibiotics is provided by TolC-like proteins, which are outer membrane components of multidrug efflux pumps. Accordingly, altered membrane permeability, including porin modifications and/or efflux pumps’ overexpression, is always associated to multidrug resistance (MDR) in a number of clinical isolates. Several recent studies have highlighted our current understanding of porins/TolC structures and functions in Enterobacteriaceae. Here, we review the transport of antibiotics through the OmpF/C general porins and the TolC-like channels with regards to recent data on their structure, function, assembly, regulation and contribution to bacterial resistance. Because MDR strains have evolved global strategies to identify and fight our antibiotic arsenal, it is important to constantly update our global knowledge on antibiotic transport.
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Affiliation(s)
- Muriel Masi
- CNRS-UMR 8619, Institut de Biophysique et de Biochimie Moléculaire et Cellulaire (IBBMC), Université Paris Sud, Orsay, France
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31
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Draft genome sequence of Enterobacter cloacae subsp. cloacae strain 08XA1, a fecal bacterium of giant pandas. J Bacteriol 2013; 194:6928-9. [PMID: 23209197 DOI: 10.1128/jb.01790-12] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Enterobacter cloacae, a common pathogenic bacterium, is a Gram-negative bacillus. We analyzed the draft genome of Enterobacter cloacae subsp. cloacae strain 08XA1 from the feces of a giant panda in China. Genes encoding a β-lactamase and efflux pumps, as well as other factors, have been found in the genome.
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32
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Staron P, Maldener I. All0809/8/7 is a DevBCA-like ABC-type efflux pump required for diazotrophic growth in Anabaena sp. PCC 7120. MICROBIOLOGY-SGM 2012; 158:2537-2545. [PMID: 22859614 DOI: 10.1099/mic.0.058909-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Efflux pumps export a wide variety of proteinaceous and non-proteinaceous substrates across the Gram-negative cell wall. For the filamentous cyanobacterium Anabaena sp. strain PCC 7120, the ATP-driven glycolipid efflux pump DevBCA-TolC has been shown to be crucial for the differentiation of N(2)-fixing heterocysts from photosynthetically active vegetative cells. In this study, a homologous system was described. All0809/8/7-TolC form a typical ATP-driven efflux pump as shown by surface plasmon resonance. This putative exporter is also involved in diazotrophic growth of Anabaena sp. PCC 7120. A mutant in all0809 encoding the periplasmic membrane fusion protein of the pump was not able to grow without combined nitrogen. Although heterocysts of this mutant were not distinguishable from those of the wild-type in light and electron micrographs, they were impaired in providing the microoxic environment necessary for N(2) fixation. RT-PCR of all0809 transcripts and localization studies on All0807-GFP revealed that All0809/8/7 was initially downregulated during heterocyst maturation and upregulated at later stages of heterocyst formation in all cells of the filament. A substrate of the efflux pump could not be identified in ATP hydrolysis assays. We discuss a role for All0809/8/7-TolC in maintaining the continuous periplasm and how this would be of special importance for heterocyst differentiation.
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Affiliation(s)
- Peter Staron
- Department of Microbiology/Organismic Interactions, IMIT - Institute of Microbiology and Infection Medicine Tübingen, University of Tübingen, 72076 Tübingen, Germany
| | - Iris Maldener
- Department of Microbiology/Organismic Interactions, IMIT - Institute of Microbiology and Infection Medicine Tübingen, University of Tübingen, 72076 Tübingen, Germany
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33
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Lee M, Jun SY, Yoon BY, Song S, Lee K, Ha NC. Membrane fusion proteins of type I secretion system and tripartite efflux pumps share a binding motif for TolC in gram-negative bacteria. PLoS One 2012; 7:e40460. [PMID: 22792337 PMCID: PMC3391258 DOI: 10.1371/journal.pone.0040460] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2012] [Accepted: 06/07/2012] [Indexed: 11/18/2022] Open
Abstract
The Hly translocator complex of Escherichia coli catalyzes type I secretion of the toxin hemolysin A (HlyA). In this complex, HlyB is an inner membrane ABC (ATP Binding Cassette)-type transporter, TolC is an outer membrane channel protein, and HlyD is a periplasmic adaptor anchored in the inner membrane that bridges HlyB to TolC. This tripartite organization is reminiscent of that of drug efflux systems such as AcrA-AcrB-TolC and MacA-MacB-TolC of E. coli. We have previously shown the crucial role of conserved residues located at the hairpin tip region of AcrA and MacA adaptors during assembly of their cognate systems. In this study, we investigated the role of the putative tip region of HlyD using HlyD mutants with single amino acid substitutions at the conserved positions. In vivo and in vitro data show that all mutations abolished HlyD binding to TolC and resulted in the absence of HlyA secretion. Together, our results suggest that, similarly to AcrA and MacA, HlyD interacts with TolC in a tip-to-tip manner. A general model in which these conserved interactions induce opening of TolC during drug efflux and type I secretion is discussed.
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Affiliation(s)
- Minho Lee
- Department of Life Science, Chung-Ang University, Seoul, Republic of Korea
| | - So-Young Jun
- Department of Manufacturing Pharmacy, College of Pharmacy, Research Institute for Drug Development, Pusan National University, Busan, Republic of Korea
| | - Bo-Young Yoon
- Department of Manufacturing Pharmacy, College of Pharmacy, Research Institute for Drug Development, Pusan National University, Busan, Republic of Korea
| | - Saemee Song
- Department of Life Science, Chung-Ang University, Seoul, Republic of Korea
| | - Kangseok Lee
- Department of Manufacturing Pharmacy, College of Pharmacy, Research Institute for Drug Development, Pusan National University, Busan, Republic of Korea
- * E-mail: (KL); (NH)
| | - Nam-Chul Ha
- Department of Life Science, Chung-Ang University, Seoul, Republic of Korea
- * E-mail: (KL); (NH)
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34
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Xu Y, Moeller A, Jun SY, Le M, Yoon BY, Kim JS, Lee K, Ha NC. Assembly and channel opening of outer membrane protein in tripartite drug efflux pumps of Gram-negative bacteria. J Biol Chem 2012; 287:11740-50. [PMID: 22308040 PMCID: PMC3320922 DOI: 10.1074/jbc.m111.329375] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Gram-negative bacteria are capable of expelling diverse xenobiotic substances from within the cell by use of three-component efflux pumps in which the energy-activated inner membrane transporter is connected to the outer membrane channel protein via the membrane fusion protein. In this work, we describe the crystal structure of the membrane fusion protein MexA from the Pseudomonas aeruginosa MexAB-OprM pump in the hexameric ring arrangement. Electron microscopy study on the chimeric complex of MexA and the outer membrane protein OprM reveals that MexA makes a tip-to-tip interaction with OprM, which suggests a docking model for MexA and OprM. This docking model agrees well with genetic results and depicts detailed interactions. Opening of the OprM channel is accompanied by the simultaneous exposure of a protein structure resembling a six-bladed cogwheel, which intermeshes with the complementary cogwheel structure in the MexA hexamer. Taken together, we suggest an assembly and channel opening model for the MexAB-OprM pump. This study provides a better understanding of multidrug resistance in Gram-negative bacteria.
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Affiliation(s)
- Yongbin Xu
- From the Department of Manufacturing Pharmacy, College of Pharmacy and Research Institute for Drug Development, Pusan National University, Busan 609-735, Korea
| | - Arne Moeller
- the National Resource for Automated Molecular Microscopy, The Scripps Research Institute, La Jolla, California 92037, and
| | - So-Young Jun
- From the Department of Manufacturing Pharmacy, College of Pharmacy and Research Institute for Drug Development, Pusan National University, Busan 609-735, Korea
| | - Minho Le
- the School of Biological Sciences, Chung-Ang University, Seoul 156-756, Korea
| | - Bo-Young Yoon
- From the Department of Manufacturing Pharmacy, College of Pharmacy and Research Institute for Drug Development, Pusan National University, Busan 609-735, Korea
| | - Jin-Sik Kim
- From the Department of Manufacturing Pharmacy, College of Pharmacy and Research Institute for Drug Development, Pusan National University, Busan 609-735, Korea
| | - Kangseok Lee
- the School of Biological Sciences, Chung-Ang University, Seoul 156-756, Korea, To whom correspondence may be addressed. Tel.: 82-2-822-5241; Fax: 82-2-825-5026; E-mail:
| | - Nam-Chul Ha
- From the Department of Manufacturing Pharmacy, College of Pharmacy and Research Institute for Drug Development, Pusan National University, Busan 609-735, Korea, , To whom correspondence may be addressed. Tel.: 82-51-510-2528; Fax: 82-51-513-6754; E-mail:
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35
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McIntosh EDG. Efflux: how bacteria use pumps to control their microenvironment. Handb Exp Pharmacol 2012:153-166. [PMID: 23090601 DOI: 10.1007/978-3-642-28951-4_10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Efflux pumps are a potent and clinically important cause of antibiotic resistance. The particular focus of this chapter is on the efflux pump as a target for antimicrobial therapy and the development of new antibacterials to address the efflux problem.Tigecycline is an example of how old antibiotics, in this case tetracyclines, which have become substrates for efflux pumps, can be extensively modified to restore antimicrobial activity and clinical efficacy.
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36
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Mealman TD, Blackburn NJ, McEvoy MM. Metal export by CusCFBA, the periplasmic Cu(I)/Ag(I) transport system of Escherichia coli. CURRENT TOPICS IN MEMBRANES 2012; 69:163-96. [PMID: 23046651 DOI: 10.1016/b978-0-12-394390-3.00007-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
High levels of metal ions have the potential to cause cellular toxicity through a variety of mechanisms; therefore, cells have developed numerous systems that regulate their intracellular concentrations. The Cus resistance system aids in protection of Escherichia coli from high levels of Cu(I) and Ag(I) by actively transporting these metal ions to the extracellular environment. The Cus system forms a continuous complex, CusCBA, that spans the inner membrane, periplasm, and outer membrane of Gram-negative bacteria, together with a novel fourth component, the periplasmic metallochaperone, CusF. The metal-binding sites of CusA, CusB, and CusF are exquisitely tuned for Cu(I) and Ag(I), and thus effectively discriminate these ions for transport from other metals that may be required in the cell. Furthermore, direct transfer of metal from protein to protein within the Cus system during the transport process is likely to reduce the potential toxicity posed by the free metal ions. Here we review the wealth of structural, biochemical, and genetic information on the Cus system, which demonstrates the many intriguing aspects of function for metal-transporting efflux systems.
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Affiliation(s)
- Tiffany D Mealman
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, USA
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37
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Staron P, Forchhammer K, Maldener I. Novel ATP-driven pathway of glycolipid export involving TolC protein. J Biol Chem 2011; 286:38202-38210. [PMID: 21917923 DOI: 10.1074/jbc.m111.269332] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Upon depletion of combined nitrogen, N(2)-fixing heterocysts are formed from vegetative cells in the case of the filamentous cyanobacterium Anabaena sp. strain PCC 7120. A heterocyst-specific layer composed of glycolipids (heterocyst envelope glycolipids (HGLs)) that functions as an O(2) diffusion barrier is deposited over the heterocyst outer membrane and is surrounded by an outermost heterocyst polysaccharide envelope. Mutations in any gene of the devBCA operon or tolC result in the absence of the HGL layer, preventing growth on N(2) used as the sole nitrogen source. However, those mutants do not have impaired HGL synthesis. In this study, we show that DevBCA and TolC form an ATP-driven efflux pump required for the export of HGLs across the Gram-negative cell wall. By performing protein-protein interaction studies (in vivo formaldehyde cross-linking, surface plasmon resonance, and isothermal titration calorimetry), we determined the kinetics and stoichiometric relations for the transport process. For sufficient glycolipid export, the membrane fusion protein DevB had to be in a hexameric form to connect the inner membrane factor DevC and the outer membrane factor TolC. A mutation that impaired the ability of DevB to form a hexameric arrangement abolished the ability of DevC to recognize its substrate. The physiological relevance of a hexameric DevB is shown in complementation studies. We provide insights into a novel pathway of glycolipid export across the Gram-negative cell wall.
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Affiliation(s)
- Peter Staron
- Department of Microbiology/Organismic Interactions, Interfaculty Institute of Microbiology and Infection Medicine Tübingen, University of Tübingen, 72076 Tübingen, Germany
| | - Karl Forchhammer
- Department of Microbiology/Organismic Interactions, Interfaculty Institute of Microbiology and Infection Medicine Tübingen, University of Tübingen, 72076 Tübingen, Germany
| | - Iris Maldener
- Department of Microbiology/Organismic Interactions, Interfaculty Institute of Microbiology and Infection Medicine Tübingen, University of Tübingen, 72076 Tübingen, Germany.
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38
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Xu Y, Lee M, Moeller A, Song S, Yoon BY, Kim HM, Jun SY, Lee K, Ha NC. Funnel-like hexameric assembly of the periplasmic adapter protein in the tripartite multidrug efflux pump in gram-negative bacteria. J Biol Chem 2011; 286:17910-20. [PMID: 21454662 DOI: 10.1074/jbc.m111.238535] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Gram-negative bacteria expel diverse toxic chemicals through the tripartite efflux pumps spanning both the inner and outer membranes. The Escherichia coli AcrAB-TolC pump is the principal multidrug exporter that confers intrinsic drug tolerance to the bacteria. The inner membrane transporter AcrB requires the outer membrane factor TolC and the periplasmic adapter protein AcrA. However, it remains ambiguous how the three proteins are assembled. In this study, a hexameric model of the adapter protein was generated based on the propensity for trimerization of a dimeric unit, and this model was further validated by presenting its channel-forming property that determines the substrate specificity. Genetic, in vitro complementation, and electron microscopic studies provided evidence for the binding of the hexameric adapter protein to the outer membrane factor in an intermeshing cogwheel manner. Structural analyses suggested that the adapter covers the periplasmic region of the inner membrane transporter. Taken together, we propose an adapter bridging model for the assembly of the tripartite pump, where the adapter protein provides a bridging channel and induces the channel opening of the outer membrane factor in the intermeshing tip-to-tip manner.
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Affiliation(s)
- Yongbin Xu
- Department of Manufacturing Pharmacy, College of Pharmacy and Research Institute for Drug Development, Pusan National University, Busan 609-735, Republic of Korea
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Switch or funnel: how RND-type transport systems control periplasmic metal homeostasis. J Bacteriol 2011; 193:2381-7. [PMID: 21398536 DOI: 10.1128/jb.01323-10] [Citation(s) in RCA: 112] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacteria have evolved several transport mechanisms to maintain metal homeostasis and to detoxify the cell. One mechanism involves an RND (resistance-nodulation-cell division protein family)-driven tripartite protein complex to extrude a variety of toxic substrates to the extracellular milieu. These efflux systems are comprised of a central RND proton-substrate antiporter, a membrane fusion protein, and an outer membrane factor. The mechanism of substrate binding and subsequent efflux has yet to be elucidated. However, the resolution of recent protein crystal structures and genetic analyses of the components of the heavy-metal efflux family of RND proteins have allowed the developments of proposals for a substrate transport pathway. Here two models of substrate extrusion through RND protein complexes of the heavy-metal efflux protein family are described. The funnel model involves the shuttling of periplasmic substrate from the membrane fusion protein to the RND transporter and further on through the outer membrane factor to the extracellular space. Conversely, the switch model requires substrate binding to the membrane fusion protein, inducing a conformational change and creating an open-access state of the tripartite protein complex. The extrusion of periplasmic substrate bypasses the membrane fusion protein, enters the RND-transporter directly via its substrate-binding site, and is ultimately eliminated through the outer membrane channel. Evidence for and against the two models is described, and we propose that current data favor the switch model.
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40
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Periplasmic domain of CusA in an Escherichia coli Cu+/Ag+ transporter has metal binding sites. J Microbiol 2011; 48:829-35. [DOI: 10.1007/s12275-010-0339-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Accepted: 10/11/2010] [Indexed: 10/18/2022]
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