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Yang T, Zou Y, Ng HL, Kumar A, Newton SM, Klebba PE. Specificity and mechanism of TonB-dependent ferric catecholate uptake by Fiu. Front Microbiol 2024; 15:1355253. [PMID: 38601941 PMCID: PMC11005823 DOI: 10.3389/fmicb.2024.1355253] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2023] [Accepted: 01/23/2024] [Indexed: 04/12/2024] Open
Abstract
We studied the Escherichia coli outer membrane protein Fiu, a presumed transporter of monomeric ferric catecholates, by introducing Cys residues in its surface loops and modifying them with fluorescein maleimide (FM). Fiu-FM bound iron complexes of the tricatecholate siderophore enterobactin (FeEnt) and glucosylated enterobactin (FeGEnt), their dicatecholate degradation product Fe(DHBS)2 (FeEnt*), the monocatecholates dihydroxybenzoic acid (FeDHBA) and dihydroxybenzoyl serine (FeDHBS), and the siderophore antibiotics cefiderocol (FDC) and MB-1. Unlike high-affinity ligand-gated porins (LGPs), Fiu-FM had only micromolar affinity for iron complexes. Its apparent KD values for FeDHBS, FeDHBA, FeEnt*, FeEnt, FeGEnt, FeFDC, and FeMB-1 were 0.1, 0.7, 0.7, 1.0, 0.3, 0.4, and 4 μM, respectively. Despite its broad binding abilities, the transport repertoires of E. coli Fiu, as well as those of Cir and FepA, were less broad. Fiu only transported FeEnt*. Cir transported FeEnt* and FeDHBS (weakly); FepA transported FeEnt, FeEnt*, and FeDHBA. Both Cir and FepA bound FeGEnt, albeit with lower affinity. Related transporters of Acinetobacter baumannii (PiuA, PirA, BauA) had similarly moderate affinity and broad specificity for di- or monomeric ferric catecholates. Both microbiological and radioisotopic experiments showed Fiu's exclusive transport of FeEnt*, rather than ferric monocatecholate compounds. Molecular docking and molecular dynamics simulations predicted three binding sites for FeEnt*in the external vestibule of Fiu, and a fourth site deeper in its interior. Alanine scanning mutagenesis in the outermost sites (1a, 1b, and 2) decreased FeEnt* binding affinity as much as 20-fold and reduced or eliminated FeEnt* uptake. Finally, the molecular dynamics simulations suggested a pathway of FeEnt* movement through Fiu that may generally describe the process of metal transport by TonB-dependent receptors.
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Affiliation(s)
| | | | | | | | | | - Phillip E. Klebba
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS, United States
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2
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Klebba PE, Newton SMC, Six DA, Kumar A, Yang T, Nairn BL, Munger C, Chakravorty S. Iron Acquisition Systems of Gram-negative Bacterial Pathogens Define TonB-Dependent Pathways to Novel Antibiotics. Chem Rev 2021; 121:5193-5239. [PMID: 33724814 PMCID: PMC8687107 DOI: 10.1021/acs.chemrev.0c01005] [Citation(s) in RCA: 50] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Iron is an indispensable metabolic cofactor in both pro- and eukaryotes, which engenders a natural competition for the metal between bacterial pathogens and their human or animal hosts. Bacteria secrete siderophores that extract Fe3+ from tissues, fluids, cells, and proteins; the ligand gated porins of the Gram-negative bacterial outer membrane actively acquire the resulting ferric siderophores, as well as other iron-containing molecules like heme. Conversely, eukaryotic hosts combat bacterial iron scavenging by sequestering Fe3+ in binding proteins and ferritin. The variety of iron uptake systems in Gram-negative bacterial pathogens illustrates a range of chemical and biochemical mechanisms that facilitate microbial pathogenesis. This document attempts to summarize and understand these processes, to guide discovery of immunological or chemical interventions that may thwart infectious disease.
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Affiliation(s)
- Phillip E Klebba
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas 66506, United States
| | - Salete M C Newton
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas 66506, United States
| | - David A Six
- Venatorx Pharmaceuticals, Inc., 30 Spring Mill Drive, Malvern, Pennsylvania 19355, United States
| | - Ashish Kumar
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas 66506, United States
| | - Taihao Yang
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas 66506, United States
| | - Brittany L Nairn
- Department of Biological Sciences, Bethel University, 3900 Bethel Drive, St. Paul, Minnesota 55112, United States
| | - Colton Munger
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas 66506, United States
| | - Somnath Chakravorty
- Jacobs School of Medicine and Biomedical Sciences, SUNY Buffalo, Buffalo, New York 14203, United States
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3
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Sargun A, Gerner RR, Raffatellu M, Nolan EM. Harnessing Iron Acquisition Machinery to Target Enterobacteriaceae. J Infect Dis 2020; 223:S307-S313. [PMID: 33330928 DOI: 10.1093/infdis/jiaa440] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Infections caused by Gram-negative bacteria can be challenging to treat due to the outer membrane permeability barrier and the increasing emergence of antibiotic resistance. During infection, Gram-negative pathogens must acquire iron, an essential nutrient, in the host. Many Gram-negative bacteria utilize sophisticated iron acquisition machineries based on siderophores, small molecules that bind iron with high affinity. In this review, we provide an overview of siderophore-mediated iron acquisition in Enterobacteriaceae and show how these systems provide a foundation for the conceptualization and development of approaches to prevent and/or treat bacterial infections. Differences between the siderophore-based iron uptake machineries of pathogenic Enterobacteriaceae and commensal microbes may lead to the development of selective "Trojan-horse" antimicrobials and immunization strategies that will not harm the host microbiota.
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Affiliation(s)
- Artur Sargun
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Romana R Gerner
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, University of California San Diego, La Jolla, California, USA
| | - Manuela Raffatellu
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, University of California San Diego, La Jolla, California, USA.,Center for Microbiome Innovation, University of California San Diego, La Jolla, California, USA.,Chiba University-UC San Diego Center for Mucosal Immunology, Allergy, and Vaccines, La Jolla, California, USA
| | - Elizabeth M Nolan
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
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4
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Boyce JH, Dang B, Ary B, Edmondson Q, Craik CS, DeGrado WF, Seiple IB. Platform to Discover Protease-Activated Antibiotics and Application to Siderophore-Antibiotic Conjugates. J Am Chem Soc 2020; 142:21310-21321. [PMID: 33301681 DOI: 10.1021/jacs.0c06987] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Here we present a platform for discovery of protease-activated prodrugs and apply it to antibiotics that target Gram-negative bacteria. Because cleavable linkers for prodrugs had not been developed for bacterial proteases, we used substrate phage to discover substrates for proteases found in the bacterial periplasm. Rather than focusing on a single protease, we used a periplasmic extract of E. coli to find sequences with the greatest susceptibility to the endogenous mixture of periplasmic proteases. Using a fluorescence assay, candidate sequences were evaluated to identify substrates that release native amine-containing payloads. We next designed conjugates consisting of (1) an N-terminal siderophore to facilitate uptake, (2) a protease-cleavable linker, and (3) an amine-containing antibiotic. Using this strategy, we converted daptomycin-which by itself is active only against Gram-positive bacteria-into an antibiotic capable of targeting Gram-negative Acinetobacter species. We similarly demonstrated siderophore-facilitated delivery of oxazolidinone and macrolide antibiotics into a number of Gram-negative species. These results illustrate this platform's utility for development of protease-activated prodrugs, including Trojan horse antibiotics.
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Affiliation(s)
- Jonathan H Boyce
- Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94158, United States.,Cardiovascular Research Institute, University of California, San Francisco, California 94158, United States
| | - Bobo Dang
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang 310024, China.,Center for Infectious Disease Research, Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang 310024, China.,Institute of Biology, Westlake Institute for Advanced Study, Hangzhou, Zhejiang 310024, China
| | - Beatrice Ary
- Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94158, United States
| | - Quinn Edmondson
- Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94158, United States
| | - Charles S Craik
- Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94158, United States
| | - William F DeGrado
- Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94158, United States.,Cardiovascular Research Institute, University of California, San Francisco, California 94158, United States
| | - Ian B Seiple
- Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94158, United States.,Cardiovascular Research Institute, University of California, San Francisco, California 94158, United States
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5
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Olshvang E, Szebesczyk A, Kozłowski H, Hadar Y, Gumienna-Kontecka E, Shanzer A. Biomimetic ferrichrome: structural motifs for switching between narrow- and broad-spectrum activities in P. putida and E. coli. Dalton Trans 2015; 44:20850-8. [DOI: 10.1039/c5dt02685g] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Mimics with ferrichrome-like activity allowed the formulation of guidelines for broad-spectrum active compounds. Deviation from these guidelines provided narrow-spectrum active compounds.
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Affiliation(s)
- Evgenia Olshvang
- Department of Organic Chemistry
- The Weizmann Institute of Science
- Rehovot 76100
- Israel
| | | | | | - Yitzhak Hadar
- Department of Plant Pathology and Microbiology
- The R.H. Smith Faculty of Agriculture Food and Environment
- The Hebrew University of Jerusalem
- Rehovot 76100
- Israel
| | | | - Abraham Shanzer
- Department of Organic Chemistry
- The Weizmann Institute of Science
- Rehovot 76100
- Israel
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6
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Abstract
There has been considerable effort expended in the investigation of the potential of siderophore conjugates of antibiotics to circumvent the permeability barrier imposed by the outer membrane of Gram-negative bacteria. There is also a small group of natural conjugates, the sideromycins. Among the synthetic analogues that have been investigated are conjugates of nucleosides, glycopeptides, macrolides, fluroquinolones, and, above all, β-lactams. Despite this effort, few compounds have progressed beyond experimental studies. One compound, the siderophore monosulfactam BAL30072, is in early clinical studies.
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8
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Coronates, Spherical Containers, Bowl-Shaped Surfaces, Porous 1D-, 2D-, 3D-Metallo-Coordination Polymers, and Metallodendrimers. Top Curr Chem (Cham) 2011; 319:125-70. [DOI: 10.1007/128_2011_280] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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9
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Crusade for iron: iron uptake in unicellular eukaryotes and its significance for virulence. Trends Microbiol 2008; 16:261-8. [PMID: 18467097 DOI: 10.1016/j.tim.2008.03.005] [Citation(s) in RCA: 120] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2007] [Revised: 03/06/2008] [Accepted: 03/25/2008] [Indexed: 12/24/2022]
Abstract
The effective acquisition of iron is a pre-requisite for survival of all organisms, especially parasites that have a high iron requirement. In mammals, iron homeostasis is meticulously regulated; extracellular free iron is essentially unavailable and host iron availability has a crucial role in the host-pathogen relationship. Therefore, pathogens use specialized and effective mechanisms to acquire iron. In this review, we summarize the iron-uptake systems in eukaryotic unicellular organisms with particular focus on the pathogenic species: Candida albicans, Tritrichomonas foetus, Trypanosoma brucei and Leishmania spp. We describe the diversity of their iron-uptake mechanisms and highlight the importance of the process for virulence.
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10
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Froissard M, Belgareh-Touzé N, Dias M, Buisson N, Camadro JM, Haguenauer-Tsapis R, Lesuisse E. Trafficking of siderophore transporters in Saccharomyces cerevisiae and intracellular fate of ferrioxamine B conjugates. Traffic 2007; 8:1601-16. [PMID: 17714436 PMCID: PMC2171038 DOI: 10.1111/j.1600-0854.2007.00627.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We have studied the intracellular trafficking of Sit1 [ferrioxamine B (FOB) transporter] and Enb1 (enterobactin transporter) in Saccharomyces cerevisiae using green fluorescent protein (GFP) fusion proteins. Enb1 was constitutively targeted to the plasma membrane. Sit1 was essentially targeted to the vacuolar degradation pathway when synthesized in the absence of substrate. Massive plasma membrane sorting of Sit1 was induced by various siderophore substrates of Sit1, and by coprogen, which is not a substrate of Sit1. Thus, different siderophore transporters use different regulated trafficking processes. We also studied the fate of Sit1-mediated internalized siderophores. Ferrioxamine B was recovered in isolated vacuolar fractions, where it could be detected spectrophotometrically. Ferrioxamine B coupled to an inhibitor of mitochondrial protoporphyrinogen oxidase (acifluorfen) could not reach its target unless the cells were disrupted, confirming the tight compartmentalization of siderophores within cells. Ferrioxamine B coupled to a fluorescent moiety, FOB-nitrobenz-2-oxa-1,3-diazole, used as a Sit1-dependent iron source, accumulated in the vacuolar lumen even in mutants displaying a steady-state accumulation of Sit1 at the plasma membrane or in endosomal compartments. Thus, the fates of siderophore transporters and siderophores diverge early in the trafficking process.
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Affiliation(s)
- Marine Froissard
- Laboratoire Trafic intracellulaire des protéines dans la levure, Département de biologie Cellulaire, Institut Jacques MonodUnité Mixte de Recherche 7592 CNRS-Universités Paris 6 et 7, France
| | - Naïma Belgareh-Touzé
- Laboratoire Trafic intracellulaire des protéines dans la levure, Département de biologie Cellulaire, Institut Jacques MonodUnité Mixte de Recherche 7592 CNRS-Universités Paris 6 et 7, France
| | - Marylène Dias
- Chimie, Ingénierie Moléculaire et Matériaux d’Angers (CIMMA)Unité Mixte de Recherche 6200 CNRS, Université d’Angers, France
| | - Nicole Buisson
- Laboratoire Trafic intracellulaire des protéines dans la levure, Département de biologie Cellulaire, Institut Jacques MonodUnité Mixte de Recherche 7592 CNRS-Universités Paris 6 et 7, France
| | - Jean-Michel Camadro
- Laboratoire d’Ingénierie des Protéines et Contrôle Métabolique, Département de Biologie des Génomes, Institut Jacques MonodUnité Mixte de Recherche 7592 CNRS-Universités Paris 6 et 7, France
| | - Rosine Haguenauer-Tsapis
- Laboratoire Trafic intracellulaire des protéines dans la levure, Département de biologie Cellulaire, Institut Jacques MonodUnité Mixte de Recherche 7592 CNRS-Universités Paris 6 et 7, France
| | - Emmanuel Lesuisse
- Laboratoire d’Ingénierie des Protéines et Contrôle Métabolique, Département de Biologie des Génomes, Institut Jacques MonodUnité Mixte de Recherche 7592 CNRS-Universités Paris 6 et 7, France
- Emmanuel Lesuisse,
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11
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Abstract
In this critical review we discuss recent advances in understanding the modes of interaction of metal ions with membrane proteins, including channels, pumps, transporters, ATP-binding cassette proteins, G-protein coupled receptors, kinases and respiratory enzymes. Such knowledge provides a basis for elucidating the mechanism of action of some classes of metallodrugs, and a stimulus for the further exploration of the coordination chemistry of metal ions in membranes. Such research offers promise for the discovery of new drugs with unusual modes of action. The article will be of interest to bioinorganic chemists, chemical biologists, biochemists, pharmacologists and medicinal chemists. (247 references).
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Affiliation(s)
- Xiangyang Liang
- School of Chemistry, University of Edinburgh, King's Buildings, West Mains Road, Edinburgh, UKEH9 3JJ
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12
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Walker JR, Altman E. Biotinylation facilitates the uptake of large peptides by Escherichia coli and other gram-negative bacteria. Appl Environ Microbiol 2005; 71:1850-5. [PMID: 15812011 PMCID: PMC1082501 DOI: 10.1128/aem.71.4.1850-1855.2005] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Gram-negative bacteria such as Escherichia coli can normally only take up small peptides less than 650 Da, or five to six amino acids, in size. We have found that biotinylated peptides up to 31 amino acids in length can be taken up by E. coli and that uptake is dependent on the biotin transporter. Uptake could be competitively inhibited by free biotin or avidin and blocked by the protonophore carbonyl m-chlorophenylhydrazone and was abolished in E. coli mutants that lacked the biotin transporter. Biotinylated peptides could be used to supplement the growth of a biotin auxotroph, and the transported peptides were shown to be localized to the cytoplasm in cell fractionation experiments. The uptake of biotinylated peptides was also demonstrated for two other gram-negative bacteria, Salmonella enterica serovar Typhimurium and Pseudomonas aeruginosa. This finding may make it possible to create new peptide antibiotics that can be used against gram-negative pathogens. Researchers have used various moieties to cause the illicit transport of compounds in bacteria, and this study demonstrates the illicit transport of the largest known compound to date.
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Affiliation(s)
- Jennifer R Walker
- Department of Microbiology, Center for Molecular BioEngineering, University of Georgia, Athens, GA 30602, USA
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13
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Martínez JL, Baquero F. Interactions among strategies associated with bacterial infection: pathogenicity, epidemicity, and antibiotic resistance. Clin Microbiol Rev 2002; 15:647-79. [PMID: 12364374 PMCID: PMC126860 DOI: 10.1128/cmr.15.4.647-679.2002] [Citation(s) in RCA: 291] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Infections have been the major cause of disease throughout the history of human populations. With the introduction of antibiotics, it was thought that this problem should disappear. However, bacteria have been able to evolve to become antibiotic resistant. Nowadays, a proficient pathogen must be virulent, epidemic, and resistant to antibiotics. Analysis of the interplay among these features of bacterial populations is needed to predict the future of infectious diseases. In this regard, we have reviewed the genetic linkage of antibiotic resistance and bacterial virulence in the same genetic determinants as well as the cross talk between antibiotic resistance and virulence regulatory circuits with the aim of understanding the effect of acquisition of resistance on bacterial virulence. We also discuss the possibility that antibiotic resistance and bacterial virulence might prevail as linked phenotypes in the future. The novel situation brought about by the worldwide use of antibiotics is undoubtedly changing bacterial populations. These changes might alter the properties of not only bacterial pathogens, but also the normal host microbiota. The evolutionary consequences of the release of antibiotics into the environment are largely unknown, but most probably restoration of the microbiota from the preantibiotic era is beyond our current abilities.
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Affiliation(s)
- José L Martínez
- Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología. Servicio de Microbiología, Hospital Ramón y Cajal, Madrid, Spain.
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14
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Scott DC, Cao Z, Qi Z, Bauler M, Igo JD, Newton SM, Klebba PE. Exchangeability of N termini in the ligand-gated porins of Escherichia coli. J Biol Chem 2001; 276:13025-33. [PMID: 11278876 DOI: 10.1074/jbc.m011282200] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The ferric siderophore transporters of the Gram-negative bacterial outer membrane manifest a unique architecture: Their N termini fold into a globular domain that lodges within, and physically obstructs, a transmembrane porin beta-barrel formed by their C termini. We exchanged and deleted the N termini of two such siderophore receptors, FepA and FhuA, which recognize and transport ferric enterobactin and ferrichrome, respectively. The resultant chimeric proteins and empty beta-barrels avidly bound appropriate ligands, including iron complexes, protein toxins, and viruses. Thus, the ability to recognize and discriminate these molecules fully originates in the transmembrane beta-barrel domain. Both the hybrid and the deletion proteins also transported the ferric siderophore that they bound. The FepA constructs showed less transport activity than wild type receptor protein, but the FhuA constructs functioned with turnover numbers that were equivalent to wild type. The mutant proteins displayed the full range of transport functionalities, despite their aberrant or missing N termini, confirming (Braun, M., Killmann, H., and Braun, V. (1999) Mol. Microbiol. 33, 1037-1049) that the globular domain within the pore is dispensable to the siderophore internalization reaction, and when present, acts without specificity during solute uptake. These and other data suggest a transport process in which siderophore receptors undergo multiple conformational states that ultimately expel the N terminus from the channel concomitant with solute internalization.
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Affiliation(s)
- D C Scott
- Department of Chemistry & Biochemistry, University of Oklahoma, Norman, Oklahoma 73019, USA
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15
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Kline T, Fromhold M, McKennon TE, Cai S, Treiberg J, Ihle N, Sherman D, Schwan W, Hickey MJ, Warrener P, Witte PR, Brody LL, Goltry L, Barker LM, Anderson SU, Tanaka SK, Shawar RM, Nguyen LY, Langhorne M, Bigelow A, Embuscado L, Naeemi E. Antimicrobial effects of novel siderophores linked to beta-lactam antibiotics. Bioorg Med Chem 2000; 8:73-93. [PMID: 10968267 DOI: 10.1016/s0968-0896(99)00261-8] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
As a strategy to increase the penetration of antibiotic drugs through the outer membrane of gram-negative pathogens, facilitated transport through siderophore receptors has been frequently exploited. Hydroxamic acids, catechols, or very close isosteres of catechols, which are mimics of naturally occurring siderophores, have been used successfully as covalently linked escorting moieties, but a much wider diversity of iron binding motifs exists. This observation, coupled to the relative lack of specificity of siderophore receptors, prompted us to initiate a program to identify novel, noncatechol siderophoric structures. We screened over 300 compounds for their ability to (1) support growth in low iron medium of a Pseudomonas aeruginosa siderophore biosynthesis deletion mutant, or (2) compete with a bactericidal siderophore-antibiotic conjugate for siderophore receptor access. From these assays we identified a set of small molecules that fulfilled one or both of these criteria. We then synthesized these compounds with functional groups suitable for attachment to both monobactam and cephalosporin core structures. Siderophore-beta-lactam conjugates then were tested against a panel of Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus strains. Although several of the resultant chimeric compounds had antimicrobial activity approaching that of ceftazidime, and most compounds demonstrated very potent activity against their cellular targets, only a single compound was obtained that had enhanced, siderophore-mediated antibacterial activity. Results with tonB mutants frequently showed increased rather than decreased susceptibilities. suggesting that multiple factors influenced the intracellular concentration of the drugs.
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Affiliation(s)
- T Kline
- PathoGenesis Corporation, Seattle, WA 98119, USA.
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16
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Abstract
Siderophores are microbial iron chelating agents that sequester physiologically essential iron for microbes. Conjugation of drugs to siderophores allows use of active iron transport for microbially directed drug delivery. Syntheses and biological studies are described of the first multidrug isocyanurate-based siderophore analogues separately containing one, two, and three 5-fluorouridine (5-FU) derivatives as the drug component. The results indicate that a single siderophore can be used to deliver multiple drugs to target pathogenic microorganisms.
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Affiliation(s)
- Y Lu
- Department of Chemistry and Biochemistry, University of Notre Dame, IN 46556-5670, USA
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17
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Stocksdale MG, Ramurthy S, Miller MJ. Asymmetric Total Synthesis of an Important 3-(Hydroxymethyl)carbacephalosporin. J Org Chem 1998. [DOI: 10.1021/jo971772p] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Mark G. Stocksdale
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556
| | - Savithri Ramurthy
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556
| | - Marvin J. Miller
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556
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18
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Jiang X, Payne MA, Cao Z, Foster SB, Feix JB, Newton SM, Klebba PE. Ligand-specific opening of a gated-porin channel in the outer membrane of living bacteria. Science 1997; 276:1261-4. [PMID: 9157886 DOI: 10.1126/science.276.5316.1261] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Ligand-gated membrane channels selectively facilitate the entry of iron into prokaryotic cells. The essential role of iron in metabolism makes its acquisition a determinant of bacterial pathogenesis and a target for therapeutic strategies. In Gram-negative bacteria, TonB-dependent outer membrane proteins form energized, gated pores that bind iron chelates (siderophores) and internalize them. The time-resolved operation of the Escherichia coli ferric enterobactin receptor FepA was observed in vivo with electron spin resonance spectroscopy by monitoring the mobility of covalently bound nitroxide spin labels. A ligand-binding surface loop of FepA, which normally closes its transmembrane channel, exhibited energy-dependent structural changes during iron and toxin (colicin) transport. These changes were not merely associated with ligand binding, but occurred during ligand uptake through the outer membrane bilayer. The results demonstrate by a physical method that gated-porin channels open and close during membrane transport in vivo.
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Affiliation(s)
- X Jiang
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, OK 73019, USA
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19
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Diarra MS, Lavoie MC, Jacques M, Darwish I, Dolence EK, Dolence JA, Ghosh A, Ghosh M, Miller MJ, Malouin F. Species selectivity of new siderophore-drug conjugates that use specific iron uptake for entry into bacteria. Antimicrob Agents Chemother 1996; 40:2610-7. [PMID: 8913474 PMCID: PMC163585 DOI: 10.1128/aac.40.11.2610] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Siderophores selectively bind ferric iron and are involved in receptor-specific iron transport into bacteria. Several types of siderophores were synthesized, and growth-promoting or inhibitory activities when they were conjugated to carbacephalosporin, erythromycylamine, or nalidixic acid were investigated. Overall, 11 types of siderophores and 21 drug conjugates were tested against seven different bacterial species: Escherichia coli, Bordetella bronchiseptica, Pasteurella multocida, Pasteurella haemolytica, Streptococcus suis, Staphylococcus aureus, and Staphylococcus epidermidis. In some species, the inhibitory activities of the drug conjugates were associated with the ability of the bacteria to use the siderophore portion of the molecules for growth promotion in disc diffusion tests (0.04 mumol of conjugate or siderophore per disc). E. coli used catechol-based siderophore portions as well as hydroxamate-based tri-delta-OH-N-OH-delta-N-acetyl-L-ornithine ferric iron ligands for growth under iron-restricted conditions achieved by supplemental ethylenediamine di (O-hydroxyphenylacetic acid) (100 micrograms/ml) and was sensitive to carbacephalosporin conjugated to these siderophore types (up to a 34-mm-diameter inhibition zone). B. bronchiseptica used desferrioxamine B and an isocyanurate-based or trihydroxamate in addition to catechol-based siderophore portions for promotion but was not inhibited by beta-lactam conjugates partly because of the presence of beta-lactamase. P. multocida and P. haemolytica did not use any of the synthetic siderophores for growth promotion, and the inhibitory activities of some conjugates seemed partly linked to their ability to withhold iron from these bacteria, since individual siderophore portions showed some antibacterial effects. Individual siderophores did not promote S. suis growth in restrictive conditions, but the type of ferric iron ligands attached to beta-lactams affected inhibitory activities. The antibacterial activities of the intracellular-acting agents erythromycylamine and nalidixic acid were reduced or lost, even against S. aureus and S. epidermidis, when the agents were conjugated to siderophores. Conjugate-resistant E. coli mutants showed the absence of some iron-regulated outer membrane proteins in gel electrophoresis profiles and in specific phage or colicin sensitivity tests, implying that the drugs used outer membrane receptors of ferric complexes to get into cells.
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Affiliation(s)
- M S Diarra
- Département de Microbiologie, Faculté de Médecine et Centre de Recherche en Infectiologie, Centre de Recherche du Centre Hospitalier de l'Université Laval, Sainte-Foy, Québec, Canada
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Defined media for optimal pyoverdine production by Pseudomonas fluorescens 2-79. Appl Microbiol Biotechnol 1993. [DOI: 10.1007/bf00164461] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Brochu A, Brochu N, Nicas TI, Parr TR, Minnick AA, Dolence EK, McKee JA, Miller MJ, Lavoie MC, Malouin F. Modes of action and inhibitory activities of new siderophore-beta-lactam conjugates that use specific iron uptake pathways for entry into bacteria. Antimicrob Agents Chemother 1992; 36:2166-75. [PMID: 1444296 PMCID: PMC245471 DOI: 10.1128/aac.36.10.2166] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
We describe here the mechanism of inhibition of two new siderophore-beta-lactam conjugates against Escherichia coli X580. One conjugate is a spermidine-based catechol siderophore-carbacephalosporin (JAM-2-263), and the other is an N5-acetyl-N5-hydroxy-L-ornithine tripeptide hydroxamate siderophore-carbacephalosporin (EKD-3-88). In an agar diffusion test, both conjugates produced large inhibitory zones against strain X580. Resistant strains (i.e., JAMR and EKDR) could be isolated after exposure of X580 to the conjugates JAM-2-263 and EKD-3-88, respectively. No cross-resistance was observed in these individual isolates. JAMR and EKDR were studied further to elucidate the mechanism of inhibition of each conjugated drug. The affinities of JAM-2-263 and EKD-3-88 for penicillin-binding proteins (PBPs) of isolated inner membranes were determined by a competition assay with 125I-penicillin V. JAM-2-263 targeted primarily PBPs 1A/B and 5/6, while EKD-3-88 targeted PBPs 1A/B and 3. Strains X580, JAMR, and EKDR showed similar PBP affinities for the conjugates. However, marked changes were observed in the iron-regulated outer membrane proteins of resistant isolates grown on agar plates depleted of iron. EKDR lost the expression of FhuA (78 kDa) and its sensitivity to phages T1 and T5, whereas JAMR lost the expression of Cir (74 kDa) and its sensitivity to colicin Ia. These results revealed the requirement of FhuA and Cir for the inhibitory activities of EKD-3-88 and JAM-2-263, respectively. In an antibiotic diffusion assay, ferrichrome (1 microM) strongly antagonized the activities of both conjugates against X580 and JAMR, including the residual activity of JAM-2-263 against JAMR. However, the susceptibility of strain EKDR lacking the ferrichrome receptor (FhuA-) to the two conjugates remained the same in the presence of ferrichrome. The antagonistic effect of ferrichrome on the activity of JAM-2-263 may also indicate a role for FhuA in the activity of this beta-lactam conjugate. A FhuA- Cir- double mutant confirmed this hypothesis, since it showed a higher level of resistance to JAM-2-263. To reproduce iron-restricted in vivo growth conditions, we grew X580 and EKDR cells in diffusion chambers implanted in the peritoneal cavities of rats. Strain EKDR showed impaired growth in such a cultivation system. This is the first report of beta-lactam drug transport into E. coli cells that involves the FhuA outer membrane protein.
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Affiliation(s)
- A Brochu
- Département de Microbiologie, Centre de Recherche du Centre Hospitalier, Université Laval, Québec, Canada
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Saalfrank RW, Lurz CJ, Schobert K, Struck O, Bill E, Trautwein AX. Synthetische Siderophore vom Tetrazolylenol-Typ: Eisen(III)-Komplexe und dreidimensionale Eisen(II)-Koordinationspolymere. Angew Chem Int Ed Engl 1991. [DOI: 10.1002/ange.19911031116] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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McKee JA, Miller MJ. Synthesis, siderophore, and antimicrobial evaluation of a spermidine-based tricatecholate siderophore and carbacephalosporin conjugate. Bioorg Med Chem Lett 1991. [DOI: 10.1016/s0960-894x(01)80456-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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