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Mattioni Marchetti V, Hrabak J, Bitar I. Fosfomycin resistance mechanisms in Enterobacterales: an increasing threat. Front Cell Infect Microbiol 2023; 13:1178547. [PMID: 37469601 PMCID: PMC10352792 DOI: 10.3389/fcimb.2023.1178547] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Accepted: 05/31/2023] [Indexed: 07/21/2023] Open
Abstract
Antimicrobial resistance is well-known to be a global health and development threat. Due to the decrease of effective antimicrobials, re-evaluation in clinical practice of old antibiotics, as fosfomycin (FOS), have been necessary. FOS is a phosphonic acid derivate that regained interest in clinical practice for the treatment of complicated infection by multi-drug resistant (MDR) bacteria. Globally, FOS resistant Gram-negative pathogens are raising, affecting the public health, and compromising the use of the antibiotic. In particular, the increased prevalence of FOS resistance (FOSR) profiles among Enterobacterales family is concerning. Decrease in FOS effectiveness can be caused by i) alteration of FOS influx inside bacterial cell or ii) acquiring antimicrobial resistance genes. In this review, we investigate the main components implicated in FOS flow and report specific mutations that affect FOS influx inside bacterial cell and, thus, its effectiveness. FosA enzymes were identified in 1980 from Serratia marcescens but only in recent years the scientific community has started studying their spread. We summarize the global epidemiology of FosA/C2/L1-2 enzymes among Enterobacterales family. To date, 11 different variants of FosA have been reported globally. Among acquired mechanisms, FosA3 is the most spread variant in Enterobacterales, followed by FosA7 and FosA5. Based on recently published studies, we clarify and represent the molecular and genetic composition of fosA/C2 genes enviroment, analyzing the mechanisms by which such genes are slowly transmitting in emerging and high-risk clones, such as E. coli ST69 and ST131, and K. pneumoniae ST11. FOS is indicated as first line option against uncomplicated urinary tract infections and shows remarkable qualities in combination with other antibiotics. A rapid and accurate identification of FOSR type in Enterobacterales is difficult to achieve due to the lack of commercial phenotypic susceptibility tests and of rapid systems for MIC detection.
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Affiliation(s)
- Vittoria Mattioni Marchetti
- Department of Microbiology, Faculty of Medicine, University Hospital in Pilsen, Charles University, Pilsen, Czechia
- Biomedical Center, Faculty of Medicine, Charles University, Pilsen, Czechia
- Unit of Microbiology and Clinical Microbiology, Department of Clinical-Surgical, Diagnostic and Pediatric Sciences, University of Pavia, Pavia, Italy
| | - Jaroslav Hrabak
- Department of Microbiology, Faculty of Medicine, University Hospital in Pilsen, Charles University, Pilsen, Czechia
- Biomedical Center, Faculty of Medicine, Charles University, Pilsen, Czechia
| | - Ibrahim Bitar
- Department of Microbiology, Faculty of Medicine, University Hospital in Pilsen, Charles University, Pilsen, Czechia
- Biomedical Center, Faculty of Medicine, Charles University, Pilsen, Czechia
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Park Y, Solhtalab M, Thongsomboon W, Aristilde L. Strategies of organic phosphorus recycling by soil bacteria: acquisition, metabolism, and regulation. ENVIRONMENTAL MICROBIOLOGY REPORTS 2022; 14:3-24. [PMID: 35001516 PMCID: PMC9306846 DOI: 10.1111/1758-2229.13040] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Revised: 12/07/2021] [Accepted: 12/14/2021] [Indexed: 05/12/2023]
Abstract
Critical to meeting cellular phosphorus (P) demand, soil bacteria deploy a number of strategies to overcome limitation in inorganic P (Pi ) in soils. As a significant contributor to P recycling, soil bacteria secrete extracellular enzymes to degrade organic P (Po ) in soils into the readily bioavailable Pi . In addition, several Po compounds can be transported directly via specific transporters and subsequently enter intracellular metabolic pathways. In this review, we highlight the strategies that soil bacteria employ to recycle Po from the soil environment. We discuss the diversity of extracellular phosphatases in soils, the selectivity of these enzymes towards various Po biomolecules and the influence of the soil environmental conditions on the enzyme's activities. Moreover, we outline the intracellular metabolic pathways for Po biosynthesis and transporter-assisted Po and Pi uptake at different Pi availabilities. We further highlight the regulatory mechanisms that govern the production of phosphatases, the expression of Po transporters and the key metabolic changes in P metabolism in response to environmental Pi availability. Due to the depletion of natural resources for Pi , we propose future studies needed to leverage bacteria-mediated P recycling from the large pools of Po in soils or organic wastes to benefit agricultural productivity.
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Affiliation(s)
- Yeonsoo Park
- Department of Civil and Environmental Engineering, McCormick School of Engineering and Applied ScienceNorthwestern UniversityEvanstonIL60208USA
- Department of Biological and Environmental EngineeringCornell University, Riley‐Robb HallIthacaNY14853USA
| | - Mina Solhtalab
- Department of Civil and Environmental Engineering, McCormick School of Engineering and Applied ScienceNorthwestern UniversityEvanstonIL60208USA
- Department of Biological and Environmental EngineeringCornell University, Riley‐Robb HallIthacaNY14853USA
| | - Wiriya Thongsomboon
- Department of Civil and Environmental Engineering, McCormick School of Engineering and Applied ScienceNorthwestern UniversityEvanstonIL60208USA
- Department of Chemistry, Faculty of ScienceMahasarakham UniversityMahasarakham44150Thailand
| | - Ludmilla Aristilde
- Department of Civil and Environmental Engineering, McCormick School of Engineering and Applied ScienceNorthwestern UniversityEvanstonIL60208USA
- Department of Biological and Environmental EngineeringCornell University, Riley‐Robb HallIthacaNY14853USA
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3
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Feng J, Selvam B, Shukla D. How do antiporters exchange substrates across the cell membrane? An atomic-level description of the complete exchange cycle in NarK. Structure 2021; 29:922-933.e3. [PMID: 33836147 DOI: 10.1016/j.str.2021.03.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 01/07/2021] [Accepted: 03/19/2021] [Indexed: 11/19/2022]
Abstract
Major facilitator superfamily (MFS) proteins operate via three different mechanisms: uniport, symport, and antiport. Despite extensive investigations, the molecular understanding of antiporters is less advanced than that of other transporters due to the complex coupling between two substrates and the lack of distinct structures. We employ extensive all-atom molecular dynamics simulations to dissect the complete substrate exchange cycle of the bacterial NO3-/NO2- antiporter, NarK. We show that paired basic residues in the binding site prevent the closure of unbound protein and ensure the exchange of two substrates. Conformational transition occurs only in the presence of substrate, which weakens the electrostatic repulsion and stabilizes the transporter. Furthermore, we propose a state-dependent substrate exchange model, in which the relative spacing between the paired basic residues determines whether NO3- and NO2- bind simultaneously or sequentially. Overall, this work presents a general working model for the antiport mechanism within the MFS.
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Affiliation(s)
- Jiangyan Feng
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Balaji Selvam
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Diwakar Shukla
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; NIH Center for Macromolecular Modeling and Bioinformatics, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Center for Digital Agriculture, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
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4
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Abstract
The organic cation transporters (OCTs) OCT1, OCT2, OCT3, novel OCT (OCTN)1, OCTN2, multidrug and toxin exclusion (MATE)1, and MATE kidney-specific 2 are polyspecific transporters exhibiting broadly overlapping substrate selectivities. They transport organic cations, zwitterions, and some uncharged compounds and operate as facilitated diffusion systems and/or antiporters. OCTs are critically involved in intestinal absorption, hepatic uptake, and renal excretion of hydrophilic drugs. They modulate the distribution of endogenous compounds such as thiamine, L-carnitine, and neurotransmitters. Sites of expression and functions of OCTs have important impact on energy metabolism, pharmacokinetics, and toxicity of drugs, and on drug-drug interactions. In this work, an overview about the human OCTs is presented. Functional properties of human OCTs, including identified substrates and inhibitors of the individual transporters, are described. Sites of expression are compiled, and data on regulation of OCTs are presented. In addition, genetic variations of OCTs are listed, and data on their impact on transport, drug treatment, and diseases are reported. Moreover, recent data are summarized that indicate complex drug-drug interaction at OCTs, such as allosteric high-affinity inhibition of transport and substrate dependence of inhibitor efficacies. A hypothesis about the molecular mechanism of polyspecific substrate recognition by OCTs is presented that is based on functional studies and mutagenesis experiments in OCT1 and OCT2. This hypothesis provides a framework to imagine how observed complex drug-drug interactions at OCTs arise. Finally, preclinical in vitro tests that are performed by pharmaceutical companies to identify interaction of novel drugs with OCTs are discussed. Optimized experimental procedures are proposed that allow a gapless detection of inhibitory and transported drugs.
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Affiliation(s)
- Hermann Koepsell
- Institute of Anatomy and Cell Biology and Department of Molecular Plant Physiology and Biophysics, Julius-von-Sachs-Institute, University of Würzburg, Würzburg, Germany
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5
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Zhang T, Shi XC, Xia Y, Mai L, Tremblay PL. Escherichia coli adaptation and response to exposure to heavy atmospheric pollution. Sci Rep 2019; 9:10879. [PMID: 31350435 PMCID: PMC6659633 DOI: 10.1038/s41598-019-47427-7] [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: 11/16/2018] [Accepted: 07/16/2019] [Indexed: 12/30/2022] Open
Abstract
90% of the world population is exposed to heavy atmospheric pollution. This is a major public health issue causing 7 million death each year. Air pollution comprises an array of pollutants such as particulate matters, ozone and carbon monoxide imposing a multifactorial stress on living cells. Here, Escherichia coli was used as model cell and adapted for 390 generations to atmospheric pollution to assess its long-term effects at the genetic, transcriptomic and physiological levels. Over this period, E. coli evolved to grow faster and acquired an adaptive mutation in rpoB, which encodes the RNA polymerase β subunit. Transcriptomic and biochemical characterization showed alteration of the cell membrane composition resulting in lesser permeability after the adaptation process. A second significant change in the cell wall structure of the adapted strain was the greater accumulation of the exopolysaccharides colanic acid and cellulose in the extracellular fraction. Results also indicated that amino acids homeostasis was involved in E. coli response to atmospheric pollutants. This study demonstrates that adaptive mutation with transformative physiological impact can be fixed in genome after exposure to atmospheric pollution and also provides a comprehensive portrait of the cellular response mechanisms involved.
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Affiliation(s)
- Tian Zhang
- State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan, P.R. China.,School of Chemistry, Chemical Engineering and Life Science, Wuhan University of Technology, Wuhan, P.R. China
| | - Xiao-Chen Shi
- State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan, P.R. China.,School of Chemistry, Chemical Engineering and Life Science, Wuhan University of Technology, Wuhan, P.R. China
| | - Yangyang Xia
- State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, International School of Materials Science and Engineering, Wuhan University of Technology, Wuhan, P.R. China
| | - Liqiang Mai
- State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, International School of Materials Science and Engineering, Wuhan University of Technology, Wuhan, P.R. China
| | - Pier-Luc Tremblay
- State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan, P.R. China. .,School of Chemistry, Chemical Engineering and Life Science, Wuhan University of Technology, Wuhan, P.R. China.
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Xie X, Cheng YS, Wen MH, Calindi A, Yang K, Chiu CW, Chen TY. Quantifying the Oligomeric States of Membrane Proteins in Cells through Super-Resolution Localizations. J Phys Chem B 2018; 122:10496-10504. [PMID: 30384609 DOI: 10.1021/acs.jpcb.8b10402] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Transitions between different oligomeric states of membrane proteins are essential for proper cellular functions. However, the quantification of their oligomeric states in cells is technically challenging. Here we developed a new method to quantify oligomeric state(s) of highly expressed membrane proteins using the probability density function of molecule density ( PDFMD) calculated from super-resolution localizations. We provided the theoretical model of PDFMD, discussed the effects of protein concentration, cell geometry, and photophysics of fluorescent proteins on PDFMD, and provided experimental criteria for proper quantification of oligomeric states. This method was further validated using simulated single-molecule fluorescent movies and applied to two membrane proteins, UhpT and SbmA in E. coli. The study shows that PDFMD is useful in quantifying oligomeric states of membrane proteins in cells that can help in understanding cellular tasks. Potential applications to proteins with higher oligomeric states under high concentration and limitations of our methodology were also discussed.
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Affiliation(s)
- Xihong Xie
- Department of Chemistry , University of Houston , Houston , Texas 77204 , United States
| | - Yu-Shan Cheng
- Department of Chemistry , University of Houston , Houston , Texas 77204 , United States
| | - Meng-Hsuan Wen
- Department of Chemistry , University of Houston , Houston , Texas 77204 , United States
| | - Aparna Calindi
- Department of Chemistry , University of Houston , Houston , Texas 77204 , United States
| | - Karen Yang
- Department of Chemistry , University of Houston , Houston , Texas 77204 , United States
| | - Chi-Wei Chiu
- Department of Chemistry , University of Houston , Houston , Texas 77204 , United States
| | - Tai-Yen Chen
- Department of Chemistry , University of Houston , Houston , Texas 77204 , United States
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7
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Lee SH, Hong SH, Kim KR, Oh DK. High-yield production of pure tagatose from fructose by a three-step enzymatic cascade reaction. Biotechnol Lett 2017; 39:1141-1148. [PMID: 28405835 DOI: 10.1007/s10529-017-2340-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2017] [Accepted: 04/06/2017] [Indexed: 11/30/2022]
Abstract
OBJECTIVE To produce tagatose from fructose with a high conversion rate and to establish a high-yield purification method of tagatose from the reaction mixture. RESULTS Fructose at 1 M (180 g l-1) was converted to 0.8 M (144 g l-1) tagatose by a three-step enzymatic cascade reaction, involving hexokinase, plus ATP, fructose-1,6-biphosphate aldolase, phytase, over 16 h with a productivity of 9 g l-1 h-1. No byproducts were detected. Tagatose was recrystallized from ethanol to a purity of 99.9% and a yield of 96.3%. Overall, tagatose at 99.9% purity was obtained from fructose with a yield of 77%. CONCLUSION This is the first biotechnological production of tagatose from fructose and the first application of solvent recrystallization for the purification of rare sugars.
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Affiliation(s)
- Seon-Hwa Lee
- Department of Bioscience and Biotechnology, Konkuk University, Seoul, 05029, Republic of Korea
| | - Seung-Hye Hong
- Department of Bioscience and Biotechnology, Konkuk University, Seoul, 05029, Republic of Korea
| | - Kyoung-Rok Kim
- Department of Bioscience and Biotechnology, Konkuk University, Seoul, 05029, Republic of Korea
| | - Deok-Kun Oh
- Department of Bioscience and Biotechnology, Konkuk University, Seoul, 05029, Republic of Korea.
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8
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Albermann C, Weiner M, Tröndle J, Weuster-Botz D, Sprenger GA. Utilization of organophosphate:phosphate antiporter for isotope-labeling experiments in E. coli. FEMS Microbiol Lett 2014; 361:52-61. [PMID: 25273627 DOI: 10.1111/1574-6968.12612] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2014] [Revised: 09/04/2014] [Accepted: 09/25/2014] [Indexed: 12/01/2022] Open
Abstract
The transport of organophosphates across the cytoplasma membrane is mediated by organophosphate:phosphate antiporter proteins. In this work, we present the application of a recombinant phosphoenolpyruvate:phosphate antiporter for isotopic labeling experiments in E. coli strains. The antiporters UhpT, UhpT-D388C, and PgtP were investigated regarding transport activity and growth on phosphoenolpyruvate as sole carbon source. The expression of the protein variant UhpT-D388C in a shikimic acid producing E. coli strain was used to show the successful isotopic labeling of shikimic acid from extracellular phosphoenolpyruvate. The results demonstrate the possibility of a direct incorporation of exogenously applicated glycolysis intermediates into E. coli cells for 13C-labeling experiments.
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Affiliation(s)
| | - Michael Weiner
- Institute of Biochemical Engineering, Technische Universität München, Garching, Germany
| | - Julia Tröndle
- Institute of Biochemical Engineering, Technische Universität München, Garching, Germany
| | - Dirk Weuster-Botz
- Institute of Biochemical Engineering, Technische Universität München, Garching, Germany
| | - Georg A Sprenger
- Institute of Microbiology, Universität Stuttgart, Stuttgart, Germany
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9
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The Structure and Function of OxlT, the Oxalate Transporter of Oxalobacter formigenes. J Membr Biol 2014; 248:641-50. [DOI: 10.1007/s00232-014-9728-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2014] [Accepted: 09/05/2014] [Indexed: 01/01/2023]
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10
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Duddempudi PK, Nakashe P, Blanton MP, Jansen M. The monomeric state of the proton-coupled folate transporter represents the functional unit in the plasma membrane. FEBS J 2013; 280:2900-15. [PMID: 23601781 DOI: 10.1111/febs.12293] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2013] [Revised: 03/10/2013] [Accepted: 04/16/2013] [Indexed: 01/20/2023]
Abstract
Folic acid is an essential vitamin required for de novo biosynthesis of nucleotides and amino acids. The proton-coupled folate transporter (PCFT; SLC46A1) has been identified as the major contributor for intestinal folate uptake. It is also involved in folate transport across the blood-brain barrier and into solid tumors. PCFT belongs to the major facilitator superfamily. Major facilitator superfamily members can exist in either monomeric or homo-oligomeric form. Here, we utilized blue native polyacrylamide gel electrophoresis (BN/PAGE) and crosslinking with bi-functional chemicals to investigate the quaternary structure of human PCFT after heterologous expression in Xenopus laevis oocytes and CHO cells. PCFT was expressed in the plasma membrane in both expression systems. The functionality of the utilized PCFT construct was confirmed in oocytes by folic acid induced currents at acidic pH. For both the oocyte and CHO expression system [(3)H]folic acid uptake studies indicated that PCFT was functional. To analyze the oligomeric state of PCFT in the plasma membrane, plasma membranes were isolated by polymerization with colloidal silica and polyacrylic acid and subsequent centrifugation. The digitonin-solubilized non-denatured PCFT migrated during BN/PAGE as a monomer, as judged by comparison with a membrane protein (5-HT(3A) receptor) of known pentameric assembly that was used to create a molecular sizing ladder. The chemical crosslinkers glutaraldehyde and dimethyl adipimidate were not able to covalently link potential higher order PCFT structures to form oligomers that were stable following SDS treatment. Together, our results demonstrate that plasma-membrane PCFT functions as a monomeric protein.
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Affiliation(s)
- Phaneendra K Duddempudi
- Department of Pharmacology and Neuroscience, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
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11
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Castañeda-García A, Blázquez J, Rodríguez-Rojas A. Molecular Mechanisms and Clinical Impact of Acquired and Intrinsic Fosfomycin Resistance. Antibiotics (Basel) 2013; 2:217-36. [PMID: 27029300 PMCID: PMC4790336 DOI: 10.3390/antibiotics2020217] [Citation(s) in RCA: 128] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Revised: 04/05/2013] [Accepted: 04/08/2013] [Indexed: 11/16/2022] Open
Abstract
Bacterial infections caused by antibiotic-resistant isolates have become a major health problem in recent years, since they are very difficult to treat, leading to an increase in morbidity and mortality. Fosfomycin is a broad-spectrum bactericidal antibiotic that inhibits cell wall biosynthesis in both Gram-negative and Gram-positive bacteria. This antibiotic has a unique mechanism of action and inhibits the initial step in peptidoglycan biosynthesis by blocking the enzyme, MurA. Fosfomycin has been used successfully for the treatment of urinary tract infections for a long time, but the increased emergence of antibiotic resistance has made fosfomycin a suitable candidate for the treatment of infections caused by multidrug-resistant pathogens, especially in combination with other therapeutic partners. The acquisition of fosfomycin resistance could threaten the reintroduction of this antibiotic for the treatment of bacterial infection. Here, we analyse the mechanism of action and molecular mechanisms for the development of fosfomycin resistance, including the modification of the antibiotic target, reduced antibiotic uptake and antibiotic inactivation. In addition, we describe the role of each pathway in clinical isolates.
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Affiliation(s)
- Alfredo Castañeda-García
- Genome Damage and Stability Centre, University of Sussex, Falmer, Science Park Road, Brighton, East Sussex BN1 9RQ, UK.
| | - Jesús Blázquez
- Centro Nacional de Biotecnología (CSIC), Departamento de Biotecnología Microbiana, Calle Darwin 3, 28049 Madrid, Spain.
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12
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Functional and biochemical characterisation of the Escherichia coli major facilitator superfamily multidrug transporter MdtM. Biochimie 2012; 94:1334-46. [DOI: 10.1016/j.biochi.2012.03.001] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2012] [Accepted: 03/01/2012] [Indexed: 01/22/2023]
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13
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Kang DC, Venkataraman PA, Dumont ME, Maloney PC. Oligomeric state of the oxalate transporter, OxlT. Biochemistry 2011; 50:8445-53. [PMID: 21866906 DOI: 10.1021/bi201175y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
OxlT, the oxalate transporter of Oxalobacter formigenes, was studied to determine its oligomeric state in solution and in the membrane. Three independent approaches were used. First, we used triple-detector (SEC-LS) size exclusion chromatography to analyze purified OxlT in detergent/lipid micelles. These measurements evaluate protein mass in a manner independent of contributions from detergent and lipid; such work shows an average OxlT mass near 47 kDa for detergent-solubilized material, consistent with that expected for monomeric OxlT (46 kDa). A disulfide-linked OxlT mutant was used to verify that it was possible detect dimers under these conditions. A second approach used amino-reactive cross-linkers of varying spacer lengths to study OxlT in detergent/lipid micelles and in natural or artificial membranes, followed by analysis via sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These tests, performed under conditions where the presence of dimers can be documented for either of two known dimeric transporters (AdiC or TetL), indicate that OxlT exists as a monomer in the membrane and retains this status upon detergent solubilization. In a final test, we showed that reconstitution of OxlT into lipid vesicles at variable protein/lipid ratios has no effect on the specific activity of subsequent oxalate transport, as the OxlT content varies between 0.027 and 5.4 OxlT monomers/proteoliposome. We conclude that OxlT is a functional monomer in the membrane and in detergent/lipid micelles.
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Affiliation(s)
- Di-Cody Kang
- Department of Physiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, United States
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14
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Simeonova DD, Wilson MM, Metcalf WW, Schink B. Identification and heterologous expression of genes involved in anaerobic dissimilatory phosphite oxidation by Desulfotignum phosphitoxidans. J Bacteriol 2010; 192:5237-44. [PMID: 20622064 PMCID: PMC2944520 DOI: 10.1128/jb.00541-10] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2010] [Accepted: 06/28/2010] [Indexed: 12/20/2022] Open
Abstract
Desulfotignum phosphitoxidans is a strictly anaerobic, Gram-negative bacterium that utilizes phosphite as the sole electron source for homoacetogenic CO2 reduction or sulfate reduction. A genomic library of D. phosphitoxidans, constructed using the fosmid vector pJK050, was screened for clones harboring the genes involved in phosphite oxidation via PCR using primers developed based on the amino acid sequences of phosphite-induced proteins. Sequence analysis of two positive clones revealed a putative operon of seven genes predicted to be involved in phosphite oxidation. Four of these genes (ptxD-ptdFCG) were cloned and heterologously expressed in Desulfotignum balticum, a related strain that cannot use phosphite as either an electron donor or as a phosphorus source. The ptxD-ptdFCG gene cluster was sufficient to confer phosphite uptake and oxidation ability to the D. balticum host strain but did not allow use of phosphite as an electron donor for chemolithotrophic growth. Phosphite oxidation activity was measured in cell extracts of D. balticum transconjugants, suggesting that all genes required for phosphite oxidation were cloned. Genes of the phosphite gene cluster were assigned putative functions on the basis of sequence analysis and enzyme assays.
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Affiliation(s)
- Diliana Dancheva Simeonova
- Laboratory of Microbial Ecology, University of Konstanz, Germany, Department of Microbiology and Institute for Genomic Biology, University of Illinois, Urbana, Illinois
| | - Marlena Marie Wilson
- Laboratory of Microbial Ecology, University of Konstanz, Germany, Department of Microbiology and Institute for Genomic Biology, University of Illinois, Urbana, Illinois
| | - William W. Metcalf
- Laboratory of Microbial Ecology, University of Konstanz, Germany, Department of Microbiology and Institute for Genomic Biology, University of Illinois, Urbana, Illinois
| | - Bernhard Schink
- Laboratory of Microbial Ecology, University of Konstanz, Germany, Department of Microbiology and Institute for Genomic Biology, University of Illinois, Urbana, Illinois
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15
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Zheng H, Taraska J, Merz AJ, Gonen T. The prototypical H+/galactose symporter GalP assembles into functional trimers. J Mol Biol 2009; 396:593-601. [PMID: 20006622 DOI: 10.1016/j.jmb.2009.12.010] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2009] [Revised: 11/30/2009] [Accepted: 12/08/2009] [Indexed: 01/20/2023]
Abstract
Glucose is a primary source of energy for human cells. Glucose transporters form specialized membrane channels for the transport of sugars into and out of cells. Galactose permease (GalP) is the closest bacterial homolog of human facilitated glucose transporters. Here, we report the functional reconstitution and 2D crystallization of GalP. Single particle electron microscopy analysis of purified GalP shows that the protein assembles as an oligomer with three distinct densities. Reconstitution assays yield 2D GalP crystals that exhibit a hexagonal array having p3 symmetry. The projection structure of GalP at 18 A resolution shows that the protein is trimeric. Each monomer in the trimer forms its own channel, but an additional cavity (10 approximately 15 A in diameter) is apparent at the 3-fold axis of the oligomer. We show that the crystalline GalP is able to selectively bind substrate, suggesting that the trimeric form is biologically active.
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Affiliation(s)
- Hongjin Zheng
- Department of Biochemistry, University of Washington, 1705 NE Pacific Street, Seattle, WA 98195, USA
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16
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The glycerol-3-phosphate permease GlpT is the only fosfomycin transporter in Pseudomonas aeruginosa. J Bacteriol 2009; 191:6968-74. [PMID: 19734311 DOI: 10.1128/jb.00748-09] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Fosfomycin is transported into Escherichia coli via both glycerol-3-phosphate (GlpT) and a hexose phosphate transporter (UhpT). Consequently, the inactivation of either glpT or uhpT confers increased fosfomycin resistance in this species. The inactivation of other genes, including ptsI and cyaA, also confers significant fosfomycin resistance. It has been assumed that identical mechanisms are responsible for fosfomycin transport into Pseudomonas aeruginosa cells. The study of an ordered library of insertion mutants in P. aeruginosa PA14 demonstrated that only insertions in glpT confer significant resistance. To explore the uniqueness of this resistance target in P. aeruginosa, the linkage between fosfomycin resistance and the use of glycerol-3-phosphate was tested. Fosfomycin-resistant (Fos-R) mutants were obtained in LB and minimal medium containing glycerol as the sole carbon source at a frequency of 10(-6). However, no Fos-R mutants grew on plates containing fosfomycin and glycerol-3-phosphate instead of glycerol (mutant frequency, < or = 5 x 10(-11)). In addition, 10 out of 10 independent spontaneous Fos-R mutants, obtained on LB-fosfomycin, harbored mutations in glpT, and in all cases the sensitivity to fosfomycin was recovered upon complementation with the wild-type glpT gene. The analysis of these mutants provides additional insights into the structure-function relationship of glycerol-3-phosphate the transporter in P. aeruginosa. Studies with glucose-6-phosphate and different mutant derivatives strongly suggest that P. aeruginosa lacks a specific transport system for this sugar. Thus, glpT seems to be the only fosfomycin resistance mutational target in P. aeruginosa. The high frequency of Fos-R mutations and their apparent lack of fitness cost suggest that Fos-R variants will be obtained easily in vivo upon the fosfomycin treatment of P. aeruginosa infections.
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Abstract
The major facilitator superfamily (MFS) represents the largest group of secondary active membrane transporters, and its members transport a diverse range of substrates. Recent work shows that MFS antiporters, and perhaps all members of the MFS, share the same three-dimensional structure, consisting of two domains that surround a substrate translocation pore. The advent of crystal structures of three MFS antiporters sheds light on their fundamental mechanism; they operate via a single binding site, alternating-access mechanism that involves a rocker-switch type movement of the two halves of the protein. In the sn-glycerol-3-phosphate transporter (GlpT) from Escherichia coli, the substrate-binding site is formed by several charged residues and a histidine that can be protonated. Salt-bridge formation and breakage are involved in the conformational changes of the protein during transport. In this review, we attempt to give an account of a set of mechanistic principles that characterize all MFS antiporters.
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Affiliation(s)
- Christopher J. Law
- The Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine and Department of Cell Biology, New York University School of Medicine, 540 First Avenue, New York, NY 10016, U.S.A;
| | - Peter C. Maloney
- The Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine and Department of Cell Biology, New York University School of Medicine, 540 First Avenue, New York, NY 10016, U.S.A;
| | - Da-Neng Wang
- The Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine and Department of Cell Biology, New York University School of Medicine, 540 First Avenue, New York, NY 10016, U.S.A;
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18
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Law CJ, Yang Q, Soudant C, Maloney PC, Wang DN. Kinetic evidence is consistent with the rocker-switch mechanism of membrane transport by GlpT. Biochemistry 2007; 46:12190-7. [PMID: 17915951 PMCID: PMC2435215 DOI: 10.1021/bi701383g] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Secondary active transport of substrate across the cell membrane is crucial to many cellular and physiological processes. The crystal structure of one member of the secondary active transporter family, the sn-glycerol-3-phosphate (G3P) transporter (GlpT) of the inner membrane of Escherichia coli, suggests a mechanism for substrate translocation across the membrane that involves a rocker-switch-type movement of the protein. This rocker-switch mechanism makes two specific predictions with respect to kinetic behavior: the transport rate increases with the temperature, whereas the binding affinity of the transporter to a substrate is temperature-independent. In this work, we directly tested these two predictions by transport kinetics and substrate-binding experiments, integrating the data on this single system into a coherent set of observations. The transport kinetics of the physiologically relevant G3P-phosphate antiport reaction were characterized at different temperatures using both E. coli whole cells and GlpT reconstituted into proteoliposomes. Substrate-binding affinity of the transporter was measured using tryptophan fluorescence quenching in detergent solution. Indeed, the substrate transport velocity of GlpT increased dramatically with temperature. In contrast, neither the apparent Michaelis constant (Km) nor the apparent substrate-binding dissociation constant (Kd) showed temperature dependence. Moreover, GlpT-catalyzed G3P translocation exhibited a completely linear Arrhenius function with an activation energy of 35.2 kJ mol-1 for the transporter reconstituted into proteoliposomes, suggesting that the substrate-loaded transporter is delicately poised between the inward- and outward-facing conformations. When these results are taken together, they are in agreement with a rocker-switch mechanism for GlpT.
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Affiliation(s)
| | | | | | | | - Da-Neng Wang
- * To whom correspondence should be addressed. Telephone: (212) 263-8634. Fax: (212) 263-8951. E-mail:
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19
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Rimon A, Tzubery T, Padan E. Monomers of the NhaA Na+/H+ Antiporter of Escherichia coli Are Fully Functional yet Dimers Are Beneficial under Extreme Stress Conditions at Alkaline pH in the Presence of Na+ or Li+. J Biol Chem 2007; 282:26810-26821. [PMID: 17635927 DOI: 10.1074/jbc.m704469200] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
NhaA, the Na(+)/H(+) antiporter of Escherichia coli, exists in the native membrane as a homodimer of which two monomers have been suggested to be attached by a beta-hairpin at the periplasmic side of the membrane. Constructing a mutant deleted of the beta-hairpin, NhaA/Delta(Pro(45)-Asn(58)), revealed that in contrast to the dimeric mobility of native NhaA, the mutant has the mobility of a monomer in a blue native gel. Intermolecular cross-linking that monitors dimers showed that the mutant exists only as monomers in the native membrane, proteoliposomes, and when purified in beta-dodecyl maltoside micelles. Furthermore, pull-down experiments revealed that, whereas as expected for a dimer, hemagglutinin-tagged wild-type NhaA co-purified with His-tagged NhaA on a Ni(2+)-NTA affinity column, a similar version of the mutant did not. Remarkably, under routine stress conditions (0.1 m LiCl, pH 7 or 0.6 m NaCl, pH 8.3), the monomeric form of NhaA is fully functional. It conferred salt resistance to NhaA- and NhaB-deleted cells, and whether in isolated membrane vesicles or reconstituted into proteoliposomes exhibited Na(+)/H(+) antiporter activity and pH regulation very similar to wild-type dimers. Remarkably, under extreme stress conditions (0.1 m LiCl or 0.7 m NaCl at pH 8.5), the dimeric native NhaA was much more efficient than the monomeric mutant in conferring extreme stress resistance.
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Affiliation(s)
- Abraham Rimon
- Department of Biological Chemistry, Alexander Silberman Institute of Life Sciences, Hebrew University of Jerusalem, 91904 Jerusalem, Israel
| | - Tzvi Tzubery
- Department of Biological Chemistry, Alexander Silberman Institute of Life Sciences, Hebrew University of Jerusalem, 91904 Jerusalem, Israel
| | - Etana Padan
- Department of Biological Chemistry, Alexander Silberman Institute of Life Sciences, Hebrew University of Jerusalem, 91904 Jerusalem, Israel.
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20
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Veldhuis G, Hink M, Krasnikov V, van den Bogaart G, Hoeboer J, Visser AJWG, Broos J, Poolman B. The oligomeric state and stability of the mannitol transporter, EnzymeII(mtl), from Escherichia coli: a fluorescence correlation spectroscopy study. Protein Sci 2006; 15:1977-86. [PMID: 16823033 PMCID: PMC2242574 DOI: 10.1110/ps.062113906] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Numerous membrane proteins function as oligomers both at the structural and functional levels. The mannitol transporter from Escherichia coli, EnzymeII(mtl), is a member of the phosphoenolpyruvate-dependent phosphotransferase system. During the transport cycle, mannitol is phosphorylated and released into the cytoplasm as mannitol-1-phosphate. Several studies have shown that EII(mtl) functions as an oligomeric species. However, the oligomerization number and stability of the oligomeric complex during different steps of the catalytic cycle, e.g., substrate binding and/or phosphorylation of the carrier, is still under discussion. In this paper, we have addressed the oligomeric state and stability of EII(mtl) using fluorescence correlation spectroscopy. A functional double-cysteine mutant was site-specifically labeled with either Alexa Fluor 488 or Alexa Fluor 633. The subunit exchange of these two batches of proteins was followed in time during different steps of the catalytic cycle. The most important conclusions are that (1) in a detergent-solubilized state, EII(mtl) is functional as a very stable dimer; (2) the stability of the complex can be manipulated by changing the intermicellar attractive forces between PEG-based detergent micelles; (3) substrate binding destabilizes the complex whereas phosphorylation increases the stability; and (4) substrate binding to the phosphorylated species partly antagonizes the stabilizing effect.
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Affiliation(s)
- Gertjan Veldhuis
- Department of Biochemistry and Biophysical Chemistry, Groningen Biomolecular Science and Biotechnology Institute & Materials Science Centreplus, University of Groningen, The Netherlands
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21
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Vinothkumar KR, Raunser S, Jung H, Kühlbrandt W. Oligomeric structure of the carnitine transporter CaiT from Escherichia coli. J Biol Chem 2005; 281:4795-801. [PMID: 16365043 DOI: 10.1074/jbc.m508993200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The carnitine transporter CaiT from Escherichia coli belongs to the betaine, choline, and carnitine transporter family of secondary transporters. It acts as an L-carnitine/gamma-butyrobetaine exchanger and is predicted to span the membrane 12 times. Unlike the other members of this transporter family, it does not require an ion gradient and does not respond to osmotic stress (Jung, H., Buchholz, M., Clausen, J., Nietschke, M., Revermann, A., Schmid, R., and Jung, K. (2002) J. Biol. Chem. 277, 39251-39258). The structure and oligomeric state of the protein was examined in detergent and in lipid bilayers. Blue native gel electrophoresis indicated that CaiT was a trimer in detergent solution. This result was further supported by gel filtration and cross-linking studies. Electron microscopy and single particle analysis of the protein showed a triangular structure of three masses or two parallel elongated densities. Reconstitution of CaiT into lipid bilayers yielded two-dimensional crystals that indicated that CaiT was a trimer in the membrane, similar to its homologue BetP. The implications of the trimeric structure on the function of CaiT are discussed.
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22
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Geertsma ER, Duurkens RH, Poolman B. Functional interactions between the subunits of the lactose transporter from Streptococcus thermophilus. J Mol Biol 2005; 350:102-11. [PMID: 15919090 DOI: 10.1016/j.jmb.2005.04.047] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2005] [Revised: 04/21/2005] [Accepted: 04/22/2005] [Indexed: 11/16/2022]
Abstract
Although the quaternary state has been assessed in detail for only a few members of the major facilitator superfamily (MFS), it is clear that multiple oligomeric states are represented within the MFS. One of its members, the lactose transporter LacS from Streptococcus thermophilus assumes a dimeric structure in the membrane and in vitro analysis showed functional interactions between both subunits when proton motive force ((Delta)p)-driven transport was assayed. To study the interactions in further detail, a covalent dimer was constructed consisting of in tandem fused LacS subunits. These covalent dimers, composed of active and completely inactive subunits, were expressed in Escherichia coli, and initial rates of (Delta)p-driven lactose uptake and lactose counterflow were determined. We now show that also in vivo, both subunits interact functionally; that is, partial complementation of the inactive subunit was observed for both transport modes. Thus, both subunits interact functionally in (Delta)p-driven uptake and in counterflow transport. In addition, analysis of in tandem fused LacS subunits containing one regulatory LacS-IIA domain showed that regulation is primarily an intramolecular event.
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Affiliation(s)
- Eric R Geertsma
- Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
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23
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Safferling M, Griffith H, Jin J, Sharp J, De Jesus M, Ng C, Krulwich TA, Wang DN. TetL tetracycline efflux protein from Bacillus subtilis is a dimer in the membrane and in detergent solution. Biochemistry 2004; 42:13969-76. [PMID: 14636065 PMCID: PMC3580950 DOI: 10.1021/bi035173q] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The TetL antiporter from the Bacillus subtilis inner membrane is a tetracycline-divalent cation efflux protein that is energized by the electrochemical proton gradient across the membrane. In this study, we expressed tetL in Escherichia coli and investigated the oligomeric state of TetL in the membrane and in detergent solution. Evidence for an oligomeric state of TetL emerged from SDS-PAGE and Western blot analysis of membrane samples as well as purified protein samples from cells that expressed two differently tagged TetL species. Furthermore, no formation or restoration of TetL oligomers occurred upon detergent solubilization of the membrane. Rather, oligomeric forms established in vivo persisted after solubilization. Mass spectrometry of the purified protein showed the absence of proteolysis and posttranslational modifications. Analytical size-exclusion chromatography of the purified protein revealed a dimeric TetL in dodecyl-maltoside solution. In addition, TetL dimers were found in a number of other detergents and over a wide pH range. It is therefore likely that the oligomeric form of the protein in the membrane is also a dimer.
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Affiliation(s)
- Markus Safferling
- Skirball Institute of Biomolecular Medicine and Department of Cell Biology, New York University School of Medicine, 540 First Avenue, New York, New York 10016, USA
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24
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Huang Y, Lemieux MJ, Song J, Auer M, Wang DN. Structure and mechanism of the glycerol-3-phosphate transporter from Escherichia coli. Science 2003; 301:616-20. [PMID: 12893936 DOI: 10.1126/science.1087619] [Citation(s) in RCA: 776] [Impact Index Per Article: 37.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The major facilitator superfamily represents the largest group of secondary membrane transporters in the cell. Here we report the 3.3 angstrom resolution structure of a member of this superfamily, GlpT, which transports glycerol-3-phosphate into the cytoplasm and inorganic phosphate into the periplasm. The amino- and carboxyl-terminal halves of the protein exhibit a pseudo two-fold symmetry. Closed off to the periplasm, a centrally located substrate-translocation pore contains two arginines at its closed end, which comprise the substrate-binding site. Upon substrate binding, the protein adopts a more compact conformation. We propose that GlpT operates by a single-binding site, alternating-access mechanism through a rocker-switch type of movement.
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Affiliation(s)
- Yafei Huang
- Skirball Institute of Biomolecular Medicine and Department of Cell Biology, New York University School of Medicine, 540 First Avenue, New York, NY 10016, USA
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25
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Morita T, El-Kazzaz W, Tanaka Y, Inada T, Aiba H. Accumulation of glucose 6-phosphate or fructose 6-phosphate is responsible for destabilization of glucose transporter mRNA in Escherichia coli. J Biol Chem 2003; 278:15608-14. [PMID: 12578824 DOI: 10.1074/jbc.m300177200] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Previously we found that a mutation in either pgi or pfkA, encoding phosphoglucose isomerase or phosphofructokinase A, respectively, facilitates degradation of the ptsG mRNA in an RNase E-dependent manner in Escherichia coli (1). In this study, we examined the effects of a series of glycolytic genes on the degradation of ptsG mRNA and how the mutations destabilize the ptsG mRNA. The conditional lethal mutation ts8 in fda, encoding fructose-1,6-P(2) aldolase just downstream of pfkA in the glycolytic pathway, caused the destabilization of ptsG mRNA at the nonpermissive temperature. Mutations in any other gene did not destabilize the ptsG mRNA; rather, they reduced the ptsG transcription mainly by affecting the cAMP level. The rapid degradation of ptsG mRNA in mutant strains was completely dependent upon the presence of glucose or any one of its compounds, which enter the Embden-Meyerhof glycolytic pathway before the block points. A significant increase in the intracellular glucose-6-P level was observed in the presence of glucose in the pgi strain. An overexpression of glucose-6-phosphate dehydrogenase eliminated both the accumulation and the degradation of ptsG mRNA in the pgi strain. In addition, accumulation of fructose-6-P led to the rapid degradation of ptsG mRNA in a pgi pfkA mutant strain lacking glucose-6-P. We conclude that the RNase E-dependent destabilization of ptsG mRNA occurs in response to accumulation of glucose-6-P or fructose-6-P.
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Affiliation(s)
- Teppei Morita
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa, Nagoya 464-8602, Japan
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26
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Abstract
Membranes are important sites for the regulation of metabolic functions because they contain transport molecules, which often catalyze the first step in a pathway, and signal-transduction components, which allow the cell to communicate with the environment. Given the catalytic importance of transport proteins and their role in membrane stability, it is possible that oligomerization is used to regulate their function. This review evaluates knowledge of the functions that are associated with the oligomeric organization of secondary transport proteins, which are a major class of solute-translocation systems in all living species.
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Affiliation(s)
- Liesbeth M Veenhoff
- Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4 9747 AG Groningen, The Netherlands
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27
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Heuberger EHML, Veenhoff LM, Duurkens RH, Friesen RHE, Poolman B. Oligomeric state of membrane transport proteins analyzed with blue native electrophoresis and analytical ultracentrifugation. J Mol Biol 2002; 317:591-600. [PMID: 11955011 DOI: 10.1006/jmbi.2002.5416] [Citation(s) in RCA: 132] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Blue native electrophoresis is used widely for the analysis of non-dissociated protein complexes with respect to composition, oligomeric state and molecular mass. However, the effects of detergent or dye binding on the mass and stability of the integral membrane proteins have not been studied. By comparison with analytical ultracentrifugation, we have evaluated whether the oligomeric state of membrane transport proteins is reflected reliably with blue native electrophoresis. For the analysis we have used two well-characterized transporters, that is, the major facilitator superfamily protein LacS and the phosphotransferase system EII(Mtl). For another member of the major facilitator superfamily, the xyloside transporter XylP from Lactobacillus pentosus, the complete analysis of the quaternary structure determined by analytical ultracentrifugation and freeze-fracture electron microscopy is presented. Our experiments show that during blue native electrophoresis the detergent bound to the proteins is replaced by the amphipathic Coomassie brilliant blue (CBB) dye. The mass of the bound CBB dye was quantified. Provided this additional mass of bound CBB dye is accounted for and care is taken in the choice and concentration of the detergent used, the mass of LacS, XylP and EII(Mtl) and four other membrane (transport) proteins could be deduced within 10 % error. Our data underscore the fact that the oligomeric state of many membrane transport proteins is dimeric.
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Affiliation(s)
- Esther H M L Heuberger
- Department of Biochemistry Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, the Netherlands
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28
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Friesen RH, Knol J, Poolman B. Quaternary structure of the lactose transport protein of Streptococcus thermophilus in the detergent-solubilized and membrane-reconstituted state. J Biol Chem 2000; 275:33527-35. [PMID: 10921919 DOI: 10.1074/jbc.m004066200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The quaternary structure of LacS, the lactose transporter of Streptococcus thermophilus, has been determined for the detergent-solubilized and the membrane-reconstituted state of the protein. The quaternary structure of the n-dodecyl-beta-d-maltoside-solubilized state was studied using a combination of sedimentation velocity and equilibrium centrifugation analysis. From these measurements it followed that the detergent-solubilized LacS undergoes reversible self-association with a monomer to dimer mode of association. The association constants were 5.4 +/- 3.6 and 4.4 +/- 1.0 ml mg(-1) as determined from the velocity and equilibrium sedimentation measurements, respectively. The experiments did not indicate significant changes in the shape of the protein-detergent complex or the amount of detergent bound in going from the monomeric to dimeric state of LacS. Importantly, a single Cys mutant of LacS is labeled by 2-(4'-maleimidylanilino)naphthalene-6-sulfonic acid in a substrate-dependent manner, indicating that the detergent-solubilized protein exhibits ligand binding activity. The quaternary structure of membrane-reconstituted LacS was determined by freeze-fracture electron microscopy analysis. Recent developments in the analysis of freeze-fracture images (Eskandari, S. P., Wright, E. M., Freman, M., Starace, D. M., and Zampighi, G. A. (1998) Proc. Natl. Acad. Sci. U. S. A. 95, 11235-11240) allowed us to directly correlate the cross-sectional area of the transmembrane segment to a dimeric state of the functionally membrane-reconstituted LacS protein. The cross-sectional area of the LacS protein was calibrated using the membrane-reconstituted transmembrane domain of the mannitol transporter enzyme II, an intramembrane particle for which the cross-sectional area was obtained from maps of two-dimensional crystals. The consequences of the determined quaternary structure for the transport function and regulation of LacS are discussed.
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Affiliation(s)
- R H Friesen
- Department of Biochemistry, University of Groningen, Groningen Biomolecular Sciences and Biotechnology Institute, Nijenborgh 4, 9747 AG Groningen, The Netherlands
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29
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van de Werve G, Lange A, Newgard C, Méchin MC, Li Y, Berteloot A. New lessons in the regulation of glucose metabolism taught by the glucose 6-phosphatase system. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:1533-49. [PMID: 10712583 DOI: 10.1046/j.1432-1327.2000.01160.x] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The operation of glucose 6-phosphatase (EC 3.1.3.9) (Glc6Pase) stems from the interaction of at least two highly hydrophobic proteins embedded in the ER membrane, a heavily glycosylated catalytic subunit of m 36 kDa (P36) and a 46-kDa putative glucose 6-phosphate (Glc6P) translocase (P46). Topology studies of P36 and P46 predict, respectively, nine and ten transmembrane domains with the N-terminal end of P36 oriented towards the lumen of the ER and both termini of P46 oriented towards the cytoplasm. P36 gene expression is increased by glucose, fructose 2,6-bisphosphate (Fru-2,6-P2) and free fatty acids, as well as by glucocorticoids and cyclic AMP; the latter are counteracted by insulin. P46 gene expression is affected by glucose, insulin and cyclic AMP in a manner similar to P36. Accordingly, several response elements for glucocorticoids, cyclic AMP and insulin regulated by hepatocyte nuclear factors were found in the Glc6Pase promoter. Mutations in P36 and P46 lead to glycogen storage disease (GSD) type-1a and type-1 non a (formerly 1b and 1c), respectively. Adenovirus-mediated overexpression of P36 in hepatocytes and in vivo impairs glycogen metabolism and glycolysis and increases glucose production; P36 overexpression in INS-1 cells results in decreased glycolysis and glucose-induced insulin secretion. The nature of the interaction between P36 and P46 in controling Glc6Pase activity remains to be defined. The latter might also have functions other than Glc6P transport that are related to Glc6P metabolism.
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Affiliation(s)
- G van de Werve
- Laboratoire d'Endocrinologie Métabolique, Centre de Recherche du CHUM,Montreal, Quebec, Canada.
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30
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Racher KI, Voegele RT, Marshall EV, Culham DE, Wood JM, Jung H, Bacon M, Cairns MT, Ferguson SM, Liang WJ, Henderson PJ, White G, Hallett FR. Purification and reconstitution of an osmosensor: transporter ProP of Escherichia coli senses and responds to osmotic shifts. Biochemistry 1999; 38:1676-84. [PMID: 10026245 DOI: 10.1021/bi981279n] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The ProP protein of Escherichia coli is an osmoregulatory H+-compatible solute cotransporter. ProP is activated by an osmotic upshift in both whole cells and membrane vesicles. We are using biochemical and biophysical techniques to explore the osmosensory and catalytic mechanisms of ProP. We now report the purification and reconstitution of the active transporter. Protein purification was facilitated by the addition of six histidine (His) codons to the 3' end of proP. The recombinant gene was overexpressed from the E. coli galP promoter, and ProP-(His)6 was shown to be functionally equivalent to wild-type ProP by enzymatic assay of whole cells. ProP-(His)6, purified by Ni2+ (NTA) affinity chromatography, cross-reacted with antibodies raised against the ProP protein. ProP-(His)6 was reconstituted into Triton X-100 destabilized liposomes prepared with E. coli phospholipid. The reconstituted transporter mediated proline accumulation only if (1) a membrane potential was generated by valinomycin-mediated K+ efflux and (2) the proteoliposomes were subjected to an osmotic upshift (0.6 M sucrose). Activity was also stimulated by DeltapH. Pure ProP acts, in the proteoliposome environment, as sensor, transducer, and respondent to a hyperosmotic shift. It is the first such osmosensor to be isolated.
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Affiliation(s)
- K I Racher
- Department of Physics, University of Guelph, Ontario, Canada
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31
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Ambudkar SV, Lelong IH, Zhang J, Cardarelli C. Purification and reconstitution of human P-glycoprotein. Methods Enzymol 1998; 292:492-504. [PMID: 9711577 DOI: 10.1016/s0076-6879(98)92038-9] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Human Pgp from the vinblastine-resistant cell line, KB-V1, can be purified by sequential conventional chromatography on DEAE-sepharose CL-6B resin followed by a wheat germ agglutinin column. By including glycerol (osmolyte protectant) and lipid during the solubilization and chromatography procedures most of the biological activity of Pgp can be retained. The activity of Pgp in the detergent extract or in the concentrated column fractions is stable for at least 8-10 months when stored at -80 degrees. However, repeated cycles of freezing and thawing of fractions result in considerable loss of activity. We have purified Pgp from KB-C1 (a subclone of KB 3-1 that is resistant to 1 microgram/ml colchicine) by following the same protocol. When this method was used for purification of Pgp from MDR1-transfected NIH 3T3 transfectants (N3-V2400, grown in the presence of 2.4 micrograms/ml vinblastine), the protein was eluted with 0.1 M NaCl from the DEAE-Sepharose CL-6B column as usual. However, during WGA lectin chromatography, the protein was eluted with a lower concentration of sugar (0.1 M instead of 0.25 M NAG). This altered elution pattern appears to be due to a difference in the glycosylation of human Pgp in mouse NIH 3T3 cells. This is consistent with the observation that human Pgp expressed in NIH 3T3 cells migrates faster compared to the protein from KB-V1 cells on 8-10% acrylamide gel. Similarly, other workers have purified Chinese hamster Pgp either by a single-step chromatography on Reactive Red 120 agarose or by a combination of anion exchange and immunoaffinity chromatography (see the article by Senior et al. for the purification and properties of ATPase activity of Chinese hamster Pgp). The high level of drug-stimulated ATP hydrolysis by Pgp (Table I), like other ion-transporting ATPases, indicates that this is a high-capacity pump that can function as an effective multidrug transporter. This is further supported by the qualitative demonstration of ATP-dependent vinblastine transport in proteoliposomes reconstituted with pure Pgp (see Fig. 2). Thus, these experiments provide strong evidence that purified Pgp retains its activity and that it functions as an ATP-dependent drug transporter.
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Affiliation(s)
- S V Ambudkar
- Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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Ramachandra M, Ambudkar SV, Chen D, Hrycyna CA, Dey S, Gottesman MM, Pastan I. Human P-glycoprotein exhibits reduced affinity for substrates during a catalytic transition state. Biochemistry 1998; 37:5010-9. [PMID: 9538020 DOI: 10.1021/bi973045u] [Citation(s) in RCA: 196] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Human P-glycoprotein (Pgp), a plasma membrane protein that confers multidrug resistance, functions as an ATP-dependent drug efflux pump. Pgp contains two ATP binding/utilization sites and exhibits ATPase activity that is stimulated in the presence of substrates and modulating agents. The mechanism of coupling of ATP hydrolysis to drug transport is not known. To understand the role of ATP hydrolysis in drug binding, it is necessary to develop methods for purifying and reconstituting Pgp that retains properties including stimulation of ATPase activity by known substrates to an extent similar to that in the native membrane. In this study, (His)6-tagged Pgp was expressed in Trichoplusia ni (High Five) cells using the recombinant baculovirus system and purified by metal affinity chromatography. Upon reconstitution into phospholipid vesicles, purified Pgp exhibited specific binding to analogues of substrates and ATP in affinity labeling experiments and displayed a high level of drug-stimulated ATPase activity (specific activity ranging from 4.5 to 6.5 micromol min-1 mg-1). The ATPase activity was inhibited by ADP in a competitive manner, and by vanadate and N-ethylmaleimide at low concentrations. Vanadate which is known to inhibit ATPase activity by trapping MgADP at the catalytic site inhibited photoaffinity labeling of Pgp with substrate analogues, [125I]iodoarylazidoprazosin and [3H]azidopine, only under ATP hydrolysis conditions. Because vanadate-trapped Pgp is known to resemble the ADP and phosphate-bound catalytic transition state, our findings indicate that ATP hydrolysis results in a conformation with reduced affinity for substrates. A catalytic transition conformation with reduced affinity would essentially result in substrate dissociation and supports a model for drug transport in which an ATP hydrolysis-induced conformational change leads to drug release toward the extracellular medium.
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Affiliation(s)
- M Ramachandra
- Laboratory of Molecular Biology, Division of Basic Sciences, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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Tamai E, Fann MC, Tsuchiya T, Maloney PC. Purification of UhpT, the sugar phosphate transporter of Escherichia coli. Protein Expr Purif 1997; 10:275-82. [PMID: 9226724 DOI: 10.1006/prep.1997.0754] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
To purify UhpT, the sugar phosphate carrier of Escherichia coli, we constructed a variant (HisUhpT) in which 10 tandem histidine residues were placed at the UhpT N terminus and then used Ni(2+)-agarose affinity chromatography of detergent-solubilized proteins. Membrane vesicles from a strain overexpressing His-UhpT were extracted at pH 7.4 with either 1.5% n-octyl-beta-D-glucopyranoside (octylglucoside) or 1.5% n-dodecyl-beta-D-maltoside (dodecylmaltoside) in 200 mM sodium chloride, 100 mM potassium phosphate, 50 mM glucose 6-phosphate, 10-20% glycerol, 0.2% E. coli phospholipid, and 5 mM beta-mercaptoethanol. After the detergent extract was applied to a Ni(2+)-agarose column, nonspecifically bound material was removed by washing at pH 7 with the same buffer also containing 50 mM imidazole. Purified HisUhpT was released subsequently, when sodium chloride was replaced with 300 mM imidazole or 100 mM EDTA, giving an overall yield of about 25 micrograms HisUhpT/mg vesicle protein. Whether eluted by imidazole or EDTA in either octylglucoside or dodecylmaltoside, purified HisUhpT showed a specific activity of 2.5-3 mumol/min per milligram of protein as monitored by [14C]glucose 6-phosphate transport by proteoliposomes loaded with 100 mM potassium phosphate. This corresponded to a calculated turnover number near 20 s-1 for the heterologous exchange of external sugar phosphate with internal phosphate. At low temperature (4 degrees C) HisUhpT retained full activity in either octylglucoside or dodecylmaltoside; however, at elevated temperature (> or = 23 degrees C), the protein displayed a marked lability in octylglucoside (t1/2 = 11 min), but not in dodecylmaltoside (t1/2 > or = 200-300 min).
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Affiliation(s)
- E Tamai
- Department of Physiology, Johns Hopkins Medical School, Baltimore, Maryland 21205, USA
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Abe K, Ruan ZS, Maloney PC. Cloning, sequencing, and expression in escherichia coli of OxlT, the oxalate:formate exchange protein of Oxalobacter formigenes. J Biol Chem 1996; 271:6789-93. [PMID: 8636101 DOI: 10.1074/jbc.271.12.6789] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
OxlT is the oxalate/formate exchange protein that represents the vectorial component of a proton-motive metabolic cycle in Oxalobacter formigenes. Here we report the cloning and sequencing of OxlT and describe its expression in Escherichia coli. The OxlT amino acid sequence specifies a polytopic hydrophobic protein of 418 residues with a mass of 44,128 daltons. Analysis of hydropathy and consideration of the distribution of charged residues suggests an OxlT secondary structure having 12 transmembrane segments, oriented so that the N and C termini face the cytoplasm. Expression of OxlT in E. coli coincides with appearance of a capacity to carry out the self-exchange of oxalate and the heterologous, electrogenic exchange of oxalate with formate. The unusually high velocity of OxlT-mediated transport is also preserved in E. coli. We conclude that the essential features of OxlT are retained on its expression in E. coli.
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Affiliation(s)
- K Abe
- Department of Physiology, Johns Hopkins Medical School, Baltimore, Maryland 21205, USA
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35
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Pos KM, Dimroth P. Functional properties of the purified Na(+)-dependent citrate carrier of Klebsiella pneumoniae: evidence for asymmetric orientation of the carrier protein in proteoliposomes. Biochemistry 1996; 35:1018-26. [PMID: 8547237 DOI: 10.1021/bi951609t] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The sodium-ion-dependent citrate carrier of Klebsiella pneumoniae (CitS) was purified and reconstituted into liposomes to investigate the properties of this transport system without interference from other proteins. Citrate uptake was an electroneutral process, where delta pNa+ and/or delta pH are driving forces. Delta psi was unable to stimulate citrate transport, either alone or in addition to the other driving forces. Sodium ions on the inside of the proteoliposomes stimulated the uptake of citrate, indicating that Na+ ions recycle during the transport of citrate. CitS also performed Na+ counterflow in the absence of citrate. The citrate carrier performed citrate/citrate counterflow but no heterologous antiport of citrate with one of the end products arising from the anaerobic citrate fermentation pathway (acetate, formate, or bicarbonate) in K. pneumoniae. Citrate counterflow kinetics revealed that CitS transports citrate according to a simultaneous type of mechanism. The Km and Ki values revealed two binding sites for citrate: one with low and one with high affinity. This transport mode is in accord with an asymmetric organization of the carrier protein in proteoliposomes.
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Affiliation(s)
- K M Pos
- Mikrobiologisches Institut, Eidgenössische Technische Hochschule, ETH-Zentrum, Zürich, Switzerland
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36
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Abstract
This article summarizes the study of anion exchange mechanisms in bacteria. Along with defining at least two different families of anion exchange, an examination of such carrier-mediated antiport reactions has led to techniques that considerably broaden the scope of biochemical methods for examining membrane proteins. Such advances have been exploited to show that anion exchange itself forms the mechanistic base of an entirely new kind of proton pump, one which may shed light on a variety of bacterial events, including methanogenesis. Perhaps most important, the study of exchange provided the final link in a chain of evidence pointing to a structural 'rhythm' that seems to characterize membrane carriers. These three issues--a biochemical tool, a new proton pump, and a common structural rhythm--are briefly examined in the context of their origins in the analysis of bacterial anion exchange.
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Affiliation(s)
- P C Maloney
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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37
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Abstract
The overexpression of the P-glycoprotein, the MDR1 gene product, has been linked to the development of resistance to multiple cytotoxic natural product anticancer drugs in certain cancers and cell lines derived from tumors. P-glycoprotein, a member of the ATP-binding cassette (ABC) superfamily of transporters, is believed to function as an ATP-dependent drug efflux pump with broad specificity for chemically unrelated hydrophobic compounds. We review here recent studies on the purification and reconstitution of P-glycoprotein to elucidate the mechanism of drug transport. P-glycoprotein from the human carcinoma multidrug resistant cell line, KB-V1, was purified by sequential chromatography on anion exchange followed by a lectin (wheat germ agglutinin) column. Proteoliposomes reconstituted with pure protein exhibited high levels of drug-stimulated ATPase activity as well as ATP-dependent [3H]vinblastine accumulation. Both the ATPase and vinblastine transport activities of the reconstituted P-glycoprotein were inhibited by vanadate. In addition, the vinblastine transport was inhibited by verapamil and daunorubicin. These studies provide strong evidence that the human P-glycoprotein functions as an ATP-dependent drug transporter. The development of the reconstitution system and the availability of recombinant protein in large amounts due to recent advances in overexpression of P-glycoprotein in a heterologous expression system should facilitate a better understanding of the function of this novel protein.
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Affiliation(s)
- S V Ambudkar
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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Grinius LL, Goldberg EB. Bacterial multidrug resistance is due to a single membrane protein which functions as a drug pump. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(18)43980-4] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Abstract
Recent experiments in bacterial systems have established an extended database of sequences broadly relevant to all membrane transporters, allowing serious study of evolutionary relationships. The database will be especially useful in integrating conclusions derived from work with proteins in the major facilitator superfamily, because this kinship includes both eukaryotic and prokaryotic model systems. Even among carriers not linked by evolution, clear hints of functional homology have been note. Advances are also evident in the structural analysis of membrane carriers. Site-directed mutagenesis in a bacterial antiporter has shown how the translocation pathway might be identified; this should complement recent progress in preparing two-dimensional crystals of the eukaryotic anion-exchange protein, band 3. Together, these studies could soon verify or reject the idea that the transport pathway lies at the interface between the amino-terminal and carboxy-terminal helical bundles found in the hydrophobic core of most carrier proteins. If verified, the argument might allow construction of informed three-dimensional models in the absence of crystallographic evidence.
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Affiliation(s)
- P C Maloney
- Department of Physiology, Johns Hopkins Medical School, Baltimore, MD 21205
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Krämer R. Functional principles of solute transport systems: concepts and perspectives. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1185:1-34. [PMID: 7511415 DOI: 10.1016/0005-2728(94)90189-9] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- R Krämer
- Institut für Biotechnologie 1, Forschungszentrum Jülich, Germany
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41
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Lolkema JS, Enequist H, van der Rest ME. Transport of citrate catalyzed by the sodium-dependent citrate carrier of Klebsiella pneumoniae is obligatorily coupled to the transport of two sodium ions. EUROPEAN JOURNAL OF BIOCHEMISTRY 1994; 220:469-75. [PMID: 8125105 DOI: 10.1111/j.1432-1033.1994.tb18645.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Aerobically grown Escherichia coli GM48 harboring plasmid pKScitS that codes for the sodium-dependent citrate carrier from Klebsiella pneumoniae (CitS) allows initial-rate measurements of citrate uptake in whole cells. The cation stoichiometry and selectivity of CitS was studied using this experimental system. The relationship between the initial rate of uptake of citrate and the Na+ concentration was sigmoidal at pH values between 5 and 7 suggesting a Na+ stoichiometry higher than 1. Rates of uptake increased quadratically in a range of non-saturating Na+ concentrations showing that two Na+ are translocated/catalytic cycle. Symport of Na+ is absolutely required in the range pH 5-7 because no uptake could be detected in the absence of Na+. Protons cannot replace Na+ in the translocation step but the decrease in apparent affinity for Na+ towards lower pH suggests that protons can compete with Na+ for the cation-binding sites. Li+ can replace Na+ in the symport reaction but it takes about a 200-fold higher concentration of Li+ over Na+ to achieve the same rate of uptake, showing that the affinity of CitS for Li+ is much lower than for Na+. Though high Li+ concentrations have an inhibitory effect on citrate uptake, the data suggest that the Li+ stoichiometry is also 2.
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Affiliation(s)
- J S Lolkema
- Department of Microbiology, University of Groningen, Haren, The Netherlands
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42
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Affiliation(s)
- B Poolman
- Department of Microbiology, University of Groningen, Haren, The Netherlands
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44
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Ruan Z, Anantharam V, Crawford I, Ambudkar S, Rhee S, Allison M, Maloney P. Identification, purification, and reconstitution of OxlT, the oxalate: formate antiport protein of Oxalobacter formigenes. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)50050-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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45
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Maloney P, Anantharam V, Allison M. Measurement of the substrate dissociation constant of a solubilized membrane carrier. Substrate stabilization of OxlT, the anion exchange protein of Oxalobacter formigenes. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)50049-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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46
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Structure and regulation of the glpFK operon encoding glycerol diffusion facilitator and glycerol kinase of Escherichia coli K-12. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)42670-1] [Citation(s) in RCA: 81] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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47
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Varadhachary A, Maloney PC. Reconstitution of the phosphoglycerate transport protein of Salmonella typhimurium. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)52412-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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48
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Abstract
General principles of membrane function have been elucidated by the study of lactic acid bacteria. In this review, the operation and function of ion pumps, secondary transport systems and solute ATPases will be discussed. Despite their differences in kinetics and mechanisms between the transport systems, structural similarities can be recognized among these proteins irrespective of whether they originate from prokaryotes, lower or higher eukaryotes.
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Affiliation(s)
- P C Maloney
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
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