1
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Goult JD, Van DCL, Taylor YV, Inns PG, Kaminska R, Vesely M, Kleanthous C, Paci E. Structural constraints of pyocin S2 import through the ferripyoverdine receptor FpvAI. PNAS NEXUS 2024; 3:pgae124. [PMID: 38577260 PMCID: PMC10994204 DOI: 10.1093/pnasnexus/pgae124] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/11/2024] [Accepted: 03/12/2024] [Indexed: 04/06/2024]
Abstract
TonB-dependent transporters (TBDTs) mediate energized transport of essential nutrients into gram-negative bacteria. TBDTs are increasingly being exploited for the delivery of antibiotics to drug-resistant bacteria. While much is known about ground state complexes of TBDTs, few details have emerged about the transport process itself. In this study, we exploit bacteriocin parasitization of a TBDT to probe the mechanics of transport. Previous work has shown that the N-terminal domain of Pseudomonas aeruginosa-specific bacteriocin pyocin S2 (PyoS2NTD) is imported through the pyoverdine receptor FpvAI. PyoS2NTD transport follows the opening of a proton-motive force-dependent pore through FpvAI and the delivery of its own TonB box that engages TonB. We use molecular models and simulations to formulate a complete translocation pathway for PyoS2NTD that we validate using protein engineering and cytotoxicity measurements. We show that following partial removal of the FpvAI plug domain which occludes the channel, the pyocin's N-terminus enters the channel by electrostatic steering and ratchets to the periplasm. Application of force, mimicking that exerted by TonB, leads to unraveling of PyoS2NTD as it squeezes through the channel. Remarkably, while some parts of PyoS2NTD must unfold, complete unfolding is not required for transport, a result we confirmed by disulfide bond engineering. Moreover, the section of the FpvAI plug that remains embedded in the channel appears to serve as a buttress against which PyoS2NTD is pushed to destabilize the domain. Our study reveals the limits of structural deformation that accompanies import through a TBDT and the role the TBDT itself plays in accommodating transport.
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Affiliation(s)
- Jonathan D Goult
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Daniel C L Van
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Yasmin V Taylor
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Patrick G Inns
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Renata Kaminska
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Martin Vesely
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Colin Kleanthous
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Emanuele Paci
- Dipartimento di Fisica e Astronomia, Università di Bologna, Bologna 40127, Italy
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2
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Choi GH, Fugaban JII, Dioso CM, Bucheli JEV, Holzapfel WH, Todorov SD. Antimicrobial Peptides (Bacteriocins) Produced by Lactococcus lactis and Pediococcus pentosaceus Strains with Activity Against Clinical and Food-Borne Pathogens. Probiotics Antimicrob Proteins 2023:10.1007/s12602-023-10188-x. [PMID: 38038837 DOI: 10.1007/s12602-023-10188-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/06/2023] [Indexed: 12/02/2023]
Abstract
Bacteriocins are ribosomal-synthesized peptides with antimicrobial activity, produced by different groups of bacteria, including lactic acid bacteria (LAB). Most of the produced by LAB bacteriocins can be described with rather broad spectra of inhibition and they offer suggested applications in food preservation and pharmaceutical sector. Different LAB were isolated from fermented food products and fruits, obtained from the region of Pohang, Korea, and identified based on physiological, biochemical, and molecular methods. The promising isolates, Pediococcus pentosaceus 732, Lactococcus lactis 808, and Lactococcus lactis subsp. lactis 431, were identified based on biochemical, physiological, and biomolecular approaches, including 16S rRNA partial sequencing, and were evaluated for production of bacteriocin, including stability in presence of enzymes, chemicals, pH, and temperatures. Adherence properties for the expressed bacteriocins by P. pentosaceus 732, Lc. lactis 808, and Lc. lactis subsp. lactis 431 were evaluated at presence of selected chemicals, pH, and temperatures. The presence of bacteriocin genes in the strains was investigated and analyzed. The bacterial effect of bacteriocin produced by studied strains on Listeria spp. and Staphylococcus spp. has been shown for actively growing and stationary cells. Similar growth and bacteriocin production were observed when studied strains were cultured in MRS at 30 °C or 37 °C. The presence of nisin operon with some point mutations on the genomic DNA was recorded based on the performed PCR reactions targeting different genes associated with nisin expression for both lactococcal strains. Pediocin PA-1 operon was evaluated in a similar manner for P. pentosaceus 732.
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Affiliation(s)
- Gee Hyeun Choi
- ProBacLab, Department of Advanced Convergence, Handong Global University, 37554, Pohang, Gyeongbuk, Republic of Korea
| | - Joanna Ivy Irorita Fugaban
- ProBacLab, Department of Advanced Convergence, Handong Global University, 37554, Pohang, Gyeongbuk, Republic of Korea
- National Food Institute, Technical University of Denmark, Kemitorvet, DK-2800, Kgs. Lyngby, Denmark
| | - Clarizza May Dioso
- HEM Laboratory, Department of Advanced Convergence, Handong Global University, 37554, Pohang, Gyeongbuk, Republic of Korea
- Department of Molecular Biotechnology, Environmental Technology and Food Technology, Ghent University Global Campus, 119, Songdomunhawa-Ro, Yeonsu-Gu, Incheon, 21985, South Korea
| | - Jorge Enrique Vazquez Bucheli
- ProBacLab, Department of Advanced Convergence, Handong Global University, 37554, Pohang, Gyeongbuk, Republic of Korea
- HEM Laboratory, Department of Advanced Convergence, Handong Global University, 37554, Pohang, Gyeongbuk, Republic of Korea
| | - Wilhelm Heinrich Holzapfel
- HEM Laboratory, Department of Advanced Convergence, Handong Global University, 37554, Pohang, Gyeongbuk, Republic of Korea
| | - Svetoslav Dimitrov Todorov
- ProBacLab, Department of Advanced Convergence, Handong Global University, 37554, Pohang, Gyeongbuk, Republic of Korea.
- ProBacLab, Laboratório de Microbiologia de Alimentos, Departamento de Alimentos e Nutrição Experimental, Faculdade de Ciências Farmacêuticas, Universidade de São Paulo, São Paulo, SP, 05508-000, Brazil.
- CISAS-Center for Research and Development in Agrifood Systems and Sustainability, Instituto Politécnico de Viana Do Castelo, 4900-347, Viana Do Castelo, Portugal.
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3
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Lach SR, Kumar S, Kim S, Im W, Konovalova A. Conformational rearrangements in the sensory RcsF/OMP complex mediate signal transduction across the bacterial cell envelope. PLoS Genet 2023; 19:e1010601. [PMID: 36706155 PMCID: PMC9907809 DOI: 10.1371/journal.pgen.1010601] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2022] [Revised: 02/08/2023] [Accepted: 01/06/2023] [Indexed: 01/28/2023] Open
Abstract
Timely detection and repair of envelope damage are paramount for bacterial survival. The Regulator of Capsule Synthesis (Rcs) stress response can transduce the stress signals across the multilayered gram-negative cell envelope to regulate gene expression in the cytoplasm. Previous studies defined the overall pathway, which begins with the sensory lipoprotein RcsF interacting with several outer membrane proteins (OMPs). RcsF can also interact with the periplasmic domain of the negative regulator IgaA, derepressing the downstream RcsCDB phosphorelay. However, how the RcsF/IgaA interaction is regulated at the molecular level to activate the signaling in response to stress remains poorly understood. In this study, we used a site-saturated mutant library of rcsF to carry out several independent genetic screens to interrogate the mechanism of signal transduction from RcsF to IgaA. We analyzed several distinct classes of rcsF signaling mutants, and determined the region of RcsF that is critically important for signal transduction. This region is bifunctional as it is important for RcsF interaction with both IgaA and OMPs. The mutant analysis provides strong evidence for conformational changes in the RcsF/OMP complex mediating signal transduction to IgaA, and the first direct evidence that OMPs play an important regulatory role in Rcs signaling.
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Affiliation(s)
- Sarah R. Lach
- Department of Microbiology and Molecular Genetics, McGovern Medical School, The University of Texas Health Science Center at Houston (UTHealth), Houston, Texas, United States of America
- The University of Texas MD Anderson UTHealth Graduate School of Biomedical Sciences, Houston, Texas, United States of America
| | - Santosh Kumar
- Department of Microbiology and Molecular Genetics, McGovern Medical School, The University of Texas Health Science Center at Houston (UTHealth), Houston, Texas, United States of America
| | - Seonghoon Kim
- Departments of Biological Sciences, Chemistry, Bioengineering, and Computer Science and Engineering, Lehigh University, Bethlehem, Pennsylvania, United States of America
- School of Computational Sciences, Korea Institute for Advanced Study, Seoul, Republic of Korea
| | - Wonpil Im
- Departments of Biological Sciences, Chemistry, Bioengineering, and Computer Science and Engineering, Lehigh University, Bethlehem, Pennsylvania, United States of America
| | - Anna Konovalova
- Department of Microbiology and Molecular Genetics, McGovern Medical School, The University of Texas Health Science Center at Houston (UTHealth), Houston, Texas, United States of America
- The University of Texas MD Anderson UTHealth Graduate School of Biomedical Sciences, Houston, Texas, United States of America
- * E-mail:
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4
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Young JW, Zhao Z, Wason IS, Duong van Hoa F. A Dual Detergent Strategy to Capture a Bacterial Outer Membrane Proteome in Peptidiscs for Characterization by Mass Spectrometry and Binding Assays. J Proteome Res 2022; 22:1537-1545. [PMID: 36516475 DOI: 10.1021/acs.jproteome.2c00560] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The outer membrane of Gram-negative bacteria plays a critical role in protecting the cell against external stressors, including antibiotics, and therefore is a prime target for antimicrobial discovery. To facilitate the discovery efforts, a precise knowledge of the outer membrane proteome, and possible variations during pathogenesis, is important. Characterization of the bacterial outer membrane remain challenging, however, and low throughput, due to the high hydrophobicity and relatively low abundance of this cell compartment. Here we adapt our peptidisc-based method to selectively isolate the outer membrane proteome before analysis by mass spectrometry. Using a dual detergent membrane solubilization approach, followed by protein purification in peptidiscs, we capture over 70 outer membrane proteins, including 26 integral β-barrels and 26 lipoproteins. Many of these proteins are present at high peptide intensities, indicative of a high abundance in the library sample. We further show that the isolated outer membrane proteome can be employed in downstream ligand-binding assays. This peptidisc library made of outer membrane proteins may therefore be useful to systematically survey other bacterial outer membrane proteomes, but also as a nanoparticle format able to support the discovery of next-generation antimicrobials. Data are available via ProteomeXchange identifier PXD036749.
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Affiliation(s)
- John William Young
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Zhiyu Zhao
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Irvinder Singh Wason
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Franck Duong van Hoa
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
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5
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Webby MN, Oluwole AO, Pedebos C, Inns PG, Olerinyova A, Prakaash D, Housden NG, Benn G, Sun D, Hoogenboom BW, Kukura P, Mohammed S, Robinson CV, Khalid S, Kleanthous C. Lipids mediate supramolecular outer membrane protein assembly in bacteria. SCIENCE ADVANCES 2022; 8:eadc9566. [PMID: 36322653 PMCID: PMC9629720 DOI: 10.1126/sciadv.adc9566] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Accepted: 09/13/2022] [Indexed: 06/16/2023]
Abstract
β Barrel outer membrane proteins (OMPs) cluster into supramolecular assemblies that give function to the outer membrane (OM) of Gram-negative bacteria. How such assemblies form is unknown. Here, through photoactivatable cross-linking into the Escherichia coli OM, coupled with simulations, and biochemical and biophysical analysis, we uncover the basis for OMP clustering in vivo. OMPs are typically surrounded by an annular shell of asymmetric lipids that mediate higher-order complexes with neighboring OMPs. OMP assemblies center on the abundant porins OmpF and OmpC, against which low-abundance monomeric β barrels, such as TonB-dependent transporters, are packed. Our study reveals OMP-lipid-OMP complexes to be the basic unit of supramolecular OMP assembly that, by extending across the entire cell surface, couples the requisite multifunctionality of the OM to its stability and impermeability.
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Affiliation(s)
- Melissa N. Webby
- Department of Biochemistry, South Parks Road, University of Oxford, Oxford OX1 3QU, UK
| | - Abraham O. Oluwole
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford OX1 3QZ, UK
- The Kavli Institute for Nanoscience Discovery, South Parks Road, Oxford OX1 3QZ, UK
| | - Conrado Pedebos
- Department of Biochemistry, South Parks Road, University of Oxford, Oxford OX1 3QU, UK
| | - Patrick G. Inns
- Department of Biochemistry, South Parks Road, University of Oxford, Oxford OX1 3QU, UK
| | - Anna Olerinyova
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford OX1 3QZ, UK
| | - Dheeraj Prakaash
- Department of Biochemistry, South Parks Road, University of Oxford, Oxford OX1 3QU, UK
| | - Nicholas G. Housden
- Department of Biochemistry, South Parks Road, University of Oxford, Oxford OX1 3QU, UK
| | - Georgina Benn
- London Centre for Nanotechnology, University College London, London WC1H 0AH, UK
- Institute of Structural and Molecular Biology, University College London, London WC1E 6BT, UK
| | - Dawei Sun
- Structural Biology, Genentech Inc., South San Francisco, USA
| | - Bart W. Hoogenboom
- London Centre for Nanotechnology, University College London, London WC1H 0AH, UK
- Institute of Structural and Molecular Biology, University College London, London WC1E 6BT, UK
- Department of Physics and Astronomy, University College London, WC1E 6BT London, UK
| | - Philipp Kukura
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford OX1 3QZ, UK
| | - Shabaz Mohammed
- Department of Biochemistry, South Parks Road, University of Oxford, Oxford OX1 3QU, UK
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Oxford OX1 3QZ, UK
- Mechanistic Proteomics, Rosalind Franklin Institute, Harwell Campus, Didcot OX11 OFA, UK
| | - Carol V. Robinson
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford OX1 3QZ, UK
- The Kavli Institute for Nanoscience Discovery, South Parks Road, Oxford OX1 3QZ, UK
| | - Syma Khalid
- Department of Biochemistry, South Parks Road, University of Oxford, Oxford OX1 3QU, UK
| | - Colin Kleanthous
- Department of Biochemistry, South Parks Road, University of Oxford, Oxford OX1 3QU, UK
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6
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Ulhuq FR, Mariano G. Bacterial pore-forming toxins. MICROBIOLOGY (READING, ENGLAND) 2022; 168:001154. [PMID: 35333704 PMCID: PMC9558359 DOI: 10.1099/mic.0.001154] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Accepted: 02/03/2022] [Indexed: 12/11/2022]
Abstract
Pore-forming toxins (PFTs) are widely distributed in both Gram-negative and Gram-positive bacteria. PFTs can act as virulence factors that bacteria utilise in dissemination and host colonisation or, alternatively, they can be employed to compete with rival microbes in polymicrobial niches. PFTs transition from a soluble form to become membrane-embedded by undergoing large conformational changes. Once inserted, they perforate the membrane, causing uncontrolled efflux of ions and/or nutrients and dissipating the protonmotive force (PMF). In some instances, target cells intoxicated by PFTs display additional effects as part of the cellular response to pore formation. Significant progress has been made in the mechanistic description of pore formation for the different PFTs families, but in several cases a complete understanding of pore structure remains lacking. PFTs have evolved recognition mechanisms to bind specific receptors that define their host tropism, although this can be remarkably diverse even within the same family. Here we summarise the salient features of PFTs and highlight where additional research is necessary to fully understand the mechanism of pore formation by members of this diverse group of protein toxins.
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Affiliation(s)
- Fatima R. Ulhuq
- Microbes in Health and Disease Theme, Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne, UK
| | - Giuseppina Mariano
- Microbes in Health and Disease Theme, Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne, UK
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7
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Budiardjo SJ, Stevens JJ, Calkins AL, Ikujuni AP, Wimalasena VK, Firlar E, Case DA, Biteen JS, Kaelber JT, Slusky JSG. Colicin E1 opens its hinge to plug TolC. eLife 2022; 11:73297. [PMID: 35199644 PMCID: PMC9020818 DOI: 10.7554/elife.73297] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Accepted: 02/21/2022] [Indexed: 12/02/2022] Open
Abstract
The double membrane architecture of Gram-negative bacteria forms a barrier that is impermeable to most extracellular threats. Bacteriocin proteins evolved to exploit the accessible, surface-exposed proteins embedded in the outer membrane to deliver cytotoxic cargo. Colicin E1 is a bacteriocin produced by, and lethal to, Escherichia coli that hijacks the outer membrane proteins (OMPs) TolC and BtuB to enter the cell. Here, we capture the colicin E1 translocation domain inside its membrane receptor, TolC, by high-resolution cryo-electron microscopy to obtain the first reported structure of a bacteriocin bound to TolC. Colicin E1 binds stably to TolC as an open hinge through the TolC pore—an architectural rearrangement from colicin E1’s unbound conformation. This binding is stable in live E. coli cells as indicated by single-molecule fluorescence microscopy. Finally, colicin E1 fragments binding to TolC plug the channel, inhibiting its native efflux function as an antibiotic efflux pump, and heightening susceptibility to three antibiotic classes. In addition to demonstrating that these protein fragments are useful starting points for developing novel antibiotic potentiators, this method could be expanded to other colicins to inhibit other OMP functions. Bacteria are constantly warring with each other for space and resources. As a result, they have developed a range of molecular weapons to poison, damage or disable other cells. For instance, bacteriocins are proteins that can latch onto structures at the surface of enemy bacteria and push toxins through their outer membrane. Bacteria are increasingly resistant to antibiotics, representing a growing concern for modern healthcare. One way that they are able to survive is by using ‘efflux pumps’ studded through their external membranes to expel harmful drugs before these can cause damage. Budiardjo et al. wanted to test whether bacteriocins could interfere with this defence mechanism by blocking efflux pumps. Bacteriocins are usually formed of binding elements (which recognise specific target proteins) and of a ‘killer tail’ that can stab the cell. Experiments showed that the binding parts of a bacteriocin could effectively ‘plug’ efflux pumps in Escherichia coli bacteria: high-resolution molecular microscopy revealed how the bacteriocin fragment binds to the pump, while fluorescent markers showed that it attached to the surface of E. coli and stopped the efflux pumps from working. As a result, lower amounts of antibiotics were necessary to kill the bacteria when bacteriocins were present. The work by Budiardjo et al. could lead to new ways to combat bacteria that will reduce the need for current antibiotics. In the future, bacteriocins could also be harnessed to target other proteins than efflux pumps, allowing scientists to manipulate a range of bacterial processes.
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Affiliation(s)
- S Jimmy Budiardjo
- Center for Computational Biology, University of Kansas, Lawrence, United States
| | - Jacqueline J Stevens
- Department of Molecular Biosciences, University of Kansas, Lawrence, United States
| | - Anna L Calkins
- Department of Chemistry, University of Michigan, Ann Arbor, United States
| | - Ayotunde P Ikujuni
- Department of Molecular Biosciences, University of Kansas, Lawrence, United States
| | | | - Emre Firlar
- Institute for Quantitative Biomedicine, Rutgers University, Piscataway, United States
| | - David A Case
- Institute for Quantitative Biomedicine, Rutgers University, Piscataway, United States
| | - Julie S Biteen
- Department of Chemistry, University of Michigan, Ann Arbor, United States
| | - Jason T Kaelber
- Institute for Quantitative Biomedicine, Rutgers, The State University of New Jersey, Piscataway, United States
| | - Joanna S G Slusky
- Center for Computational Biology, University of Kansas, Lawrence, United States
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8
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Francis MLR, Webby MN, Housden NG, Kaminska R, Elliston E, Chinthammit B, Lukoyanova N, Kleanthous C. Porin threading drives receptor disengagement and establishes active colicin transport through Escherichia coli OmpF. EMBO J 2021; 40:e108610. [PMID: 34515361 PMCID: PMC8561637 DOI: 10.15252/embj.2021108610] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 08/09/2021] [Accepted: 08/17/2021] [Indexed: 11/24/2022] Open
Abstract
Bacteria deploy weapons to kill their neighbours during competition for resources and to aid survival within microbiomes. Colicins were the first such antibacterial system identified, yet how these bacteriocins cross the outer membrane (OM) of Escherichia coli is unknown. Here, by solving the structures of translocation intermediates via cryo‐EM and by imaging toxin import, we uncover the mechanism by which the Tol‐dependent nuclease colicin E9 (ColE9) crosses the bacterial OM. We show that threading of ColE9’s disordered N‐terminal domain through two pores of the trimeric porin OmpF causes the colicin to disengage from its primary receptor, BtuB, and reorganises the translocon either side of the membrane. Subsequent import of ColE9 through the lumen of a single OmpF subunit is driven by the proton‐motive force, which is delivered by the TolQ‐TolR‐TolA‐TolB assembly. Our study answers longstanding questions, such as why OmpF is a better translocator than OmpC, and reconciles the mechanisms by which both Tol‐ and Ton‐dependent bacteriocins cross the bacterial outer membrane.
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Affiliation(s)
| | - Melissa N Webby
- Department of Biochemistry, University of Oxford, Oxford, UK
| | | | - Renata Kaminska
- Department of Biochemistry, University of Oxford, Oxford, UK
| | - Emma Elliston
- Department of Biochemistry, University of Oxford, Oxford, UK
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9
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Sepahvandi A, Ghaffari M, Bahmanpour AH, Moztarzadeh F, Zarrintaj P, Uludağ H, Mozafari M. COVID-19: insights into virus-receptor interactions. MOLECULAR BIOMEDICINE 2021; 2:10. [PMID: 34766003 PMCID: PMC8035060 DOI: 10.1186/s43556-021-00033-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2020] [Accepted: 03/03/2021] [Indexed: 01/03/2023] Open
Abstract
The recent outbreak of Coronavirus Disease 2019 (COVID-19) calls for rapid mobilization of scientists to probe and explore solutions to this deadly disease. A limited understanding of the high transmissibility of SARS-CoV-2 (Severe acute respiratory syndrome coronavirus 2) relative to other coronavirus strains guides a deeper investigation into the virus/receptor interactions. The cutting-edge studies in thermodynamic and kinetic properties of interactions such as protein-protein interplays have been reviewed in many modeling and analysis studies. Highlighting the thermodynamic assessments of biological interactions and emphasizing the boosted transmissibility of SARS-CoV-2 despite its high similarity in structure and sequence with other coronavirus strains is an important and highly valuable investigation that can lead scientists to discover analytical and fundamental approaches in studying virus's interactions. Accordingly, we have attempted to describe the crucial factors such as conformational changes and hydrophobicity particularities that influence on thermodynamic potentials in the SARS-COV-2 S-protein adsorption process. Discussing the thermodynamic potentials and the kinetics of the SARS-CoV-2 S-protein in its interaction with the ACE2 receptors of the host cell is a fundamental approach that would be extremely valuable in designing candidate pharmaceutical agents or exploring alternative treatments.
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Affiliation(s)
- Azadeh Sepahvandi
- Department of Mechanical Engineering College of Engineering and Computing, University of South Carolina, 301 Main St, Columbia, SC 29208 USA
| | - Maryam Ghaffari
- Biomaterial Group, Faculty of Biomedical Engineering (Center of Excellence), Amirkabir University of Technology, Tehran, Iran
| | - Amir Hossein Bahmanpour
- Biomaterial Group, Faculty of Biomedical Engineering (Center of Excellence), Amirkabir University of Technology, Tehran, Iran
| | - Fathollah Moztarzadeh
- Biomaterial Group, Faculty of Biomedical Engineering (Center of Excellence), Amirkabir University of Technology, Tehran, Iran
| | - Payam Zarrintaj
- School of Chemical Engineering, Oklahoma State University, 420 Engineering North, Stillwater, OK 74078 USA
| | - Hasan Uludağ
- Department of Chemical and Material Engineering, Faculty of Engineering, University of Alberta, Edmonton, AB T6G 2V4 Canada
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, AB T6G 2E1 Canada
- Department of Biomedical Engineering, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB T6G 2R3 Canada
| | - Masoud Mozafari
- Department of Tissue Engineering & Regenerative Medicine, Faculty of Advanced Technologies in Medicine, Iran University of Medical Sciences (IUMS), Tehran, Iran
- Currently at: Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, University of Toronto, Toronto, ON Canada
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10
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Cambré A, Aertsen A. Bacterial Vivisection: How Fluorescence-Based Imaging Techniques Shed a Light on the Inner Workings of Bacteria. Microbiol Mol Biol Rev 2020; 84:e00008-20. [PMID: 33115939 PMCID: PMC7599038 DOI: 10.1128/mmbr.00008-20] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The rise in fluorescence-based imaging techniques over the past 3 decades has improved the ability of researchers to scrutinize live cell biology at increased spatial and temporal resolution. In microbiology, these real-time vivisections structurally changed the view on the bacterial cell away from the "watery bag of enzymes" paradigm toward the perspective that these organisms are as complex as their eukaryotic counterparts. Capitalizing on the enormous potential of (time-lapse) fluorescence microscopy and the ever-extending pallet of corresponding probes, initial breakthroughs were made in unraveling the localization of proteins and monitoring real-time gene expression. However, later it became clear that the potential of this technique extends much further, paving the way for a focus-shift from observing single events within bacterial cells or populations to obtaining a more global picture at the intra- and intercellular level. In this review, we outline the current state of the art in fluorescence-based vivisection of bacteria and provide an overview of important case studies to exemplify how to use or combine different strategies to gain detailed information on the cell's physiology. The manuscript therefore consists of two separate (but interconnected) parts that can be read and consulted individually. The first part focuses on the fluorescent probe pallet and provides a perspective on modern methodologies for microscopy using these tools. The second section of the review takes the reader on a tour through the bacterial cell from cytoplasm to outer shell, describing strategies and methods to highlight architectural features and overall dynamics within cells.
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Affiliation(s)
- Alexander Cambré
- KU Leuven, Department of Microbial and Molecular Systems, Faculty of Bioscience Engineering, Leuven, Belgium
| | - Abram Aertsen
- KU Leuven, Department of Microbial and Molecular Systems, Faculty of Bioscience Engineering, Leuven, Belgium
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11
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Ruhe ZC, Low DA, Hayes CS. Polymorphic Toxins and Their Immunity Proteins: Diversity, Evolution, and Mechanisms of Delivery. Annu Rev Microbiol 2020; 74:497-520. [PMID: 32680451 DOI: 10.1146/annurev-micro-020518-115638] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
All bacteria must compete for growth niches and other limited environmental resources. These existential battles are waged at several levels, but one common strategy entails the transfer of growth-inhibitory protein toxins between competing cells. These antibacterial effectors are invariably encoded with immunity proteins that protect cells from intoxication by neighboring siblings. Several effector classes have been described, each designed to breach the cell envelope of target bacteria. Although effector architectures and export pathways tend to be clade specific, phylogenetically distant species often deploy closely related toxin domains. Thus, diverse competition systems are linked through a common reservoir of toxin-immunity pairs that is shared via horizontal gene transfer. These toxin-immunity protein pairs are extraordinarily diverse in sequence, and this polymorphism underpins an important mechanism of self/nonself discrimination in bacteria. This review focuses on the structures, functions, and delivery mechanisms of polymorphic toxin effectors that mediate bacterial competition.
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Affiliation(s)
- Zachary C Ruhe
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, California 93106, USA;
| | - David A Low
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, California 93106, USA; .,Biomolecular Science and Engineering Program, University of California, Santa Barbara, California 93106, USA
| | - Christopher S Hayes
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, California 93106, USA; .,Biomolecular Science and Engineering Program, University of California, Santa Barbara, California 93106, USA
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12
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Lee S, Housden NG, Ionescu SA, Zimmer MH, Kaminska R, Kleanthous C, Bayley H. Transmembrane Epitope Delivery by Passive Protein Threading through the Pores of the OmpF Porin Trimer. J Am Chem Soc 2020; 142:12157-12166. [PMID: 32614588 PMCID: PMC7366379 DOI: 10.1021/jacs.0c02362] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Trimeric porins in the outer membrane (OM) of Gram-negative bacteria are the conduits by which nutrients and antibiotics diffuse passively into cells. The narrow gateways that porins form in the OM are also exploited by bacteriocins to translocate into cells by a poorly understood process. Here, using single-channel electrical recording in planar lipid bilayers in conjunction with protein engineering, we explicate the mechanism by which the intrinsically unstructured N-terminal translocation domain (IUTD) of the endonuclease bacteriocin ColE9 is imported passively across the Escherichia coli OM through OmpF. We show that the import is dominated by weak interactions of OmpF pores with binding epitopes within the IUTD that are orientationally biased and result in the threading of over 60 amino acids through 2 subunits of OmpF. Single-molecule kinetic analysis demonstrates that the IUTD enters from the extracellular side of OmpF and translocates to the periplasm where the polypeptide chain does an about turn in order to enter a neighboring subunit, only for some of these molecules to pop out of this second subunit before finally re-entering to form a stable complex. These intimately linked transport/binding processes generate an essentially irreversible, hook-like assembly that constrains an import activating peptide epitope between two subunits of the OmpF trimer.
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Affiliation(s)
- Sejeong Lee
- Chemistry Research Laboratory, University of Oxford, Oxford OX1 3TA, U.K
| | | | - Sandra A Ionescu
- Chemistry Research Laboratory, University of Oxford, Oxford OX1 3TA, U.K
| | - Matthew H Zimmer
- Chemistry Research Laboratory, University of Oxford, Oxford OX1 3TA, U.K
| | - Renata Kaminska
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, U.K
| | - Colin Kleanthous
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, U.K
| | - Hagan Bayley
- Chemistry Research Laboratory, University of Oxford, Oxford OX1 3TA, U.K
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13
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Atanaskovic I, Mosbahi K, Sharp C, Housden NG, Kaminska R, Walker D, Kleanthous C. Targeted Killing of Pseudomonas aeruginosa by Pyocin G Occurs via the Hemin Transporter Hur. J Mol Biol 2020; 432:3869-3880. [PMID: 32339530 PMCID: PMC7322526 DOI: 10.1016/j.jmb.2020.04.020] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Revised: 04/21/2020] [Accepted: 04/21/2020] [Indexed: 01/20/2023]
Abstract
Pseudomonas aeruginosa is a priority pathogen for the development of new antibiotics, particularly because multi-drug-resistant strains of this bacterium cause serious nosocomial infections and are the leading cause of death in cystic fibrosis patients. Pyocins, bacteriocins of P. aeruginosa, are potent and diverse protein antibiotics that are deployed during bacterial competition. Pyocins are produced by more than 90% of P. aeruginosa strains and may have utility as last resort antibiotics against this bacterium. In this study, we explore the antimicrobial activity of a newly discovered pyocin called pyocin G (PyoG). We demonstrate that PyoG has broad killing activity against a collection of clinical P. aeruginosa isolates and is active in a Galleria mellonella infection model. We go on to identify cell envelope proteins that are necessary for the import of PyoG and its killing activity. PyoG recognizes bacterial cells by binding to Hur, an outer-membrane TonB-dependent transporter. Both pyocin and Hur interact with TonB1, which in complex with ExbB-ExbD links the proton motive force generated across the inner membrane with energy-dependent pyocin translocation across the outer membrane. Inner-membrane translocation of PyoG is dependent on the conserved inner-membrane AAA+ ATPase/protease, FtsH. We also report a functional exploration of the PyoG receptor. We demonstrate that Hur can bind to hemin in vitro and that this interaction is blocked by PyoG, confirming the role of Hur in hemin acquisition.
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Affiliation(s)
- Iva Atanaskovic
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Khedidja Mosbahi
- Institute of Infection, Immunity, and Inflammation, College of Medical, Veterinary, and Life Sciences, University of Glasgow, G12 8QQ Glasgow, UK
| | - Connor Sharp
- Department of Zoology, University of Oxford, 11a Mansfield Rd, Oxford OX1 3SZ, UK
| | - Nicholas G Housden
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Renata Kaminska
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Daniel Walker
- Institute of Infection, Immunity, and Inflammation, College of Medical, Veterinary, and Life Sciences, University of Glasgow, G12 8QQ Glasgow, UK
| | - Colin Kleanthous
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
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14
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Behrens HM, Lowe ED, Gault J, Housden NG, Kaminska R, Weber TM, Thompson CMA, Mislin GLA, Schalk IJ, Walker D, Robinson CV, Kleanthous C. Pyocin S5 Import into Pseudomonas aeruginosa Reveals a Generic Mode of Bacteriocin Transport. mBio 2020; 11:e03230-19. [PMID: 32156826 PMCID: PMC7064778 DOI: 10.1128/mbio.03230-19] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Accepted: 01/28/2020] [Indexed: 11/20/2022] Open
Abstract
Pyocin S5 (PyoS5) is a potent protein bacteriocin that eradicates the human pathogen Pseudomonas aeruginosa in animal infection models, but its import mechanism is poorly understood. Here, using crystallography, biophysical and biochemical analyses, and live-cell imaging, we define the entry process of PyoS5 and reveal links to the transport mechanisms of other bacteriocins. In addition to its C-terminal pore-forming domain, elongated PyoS5 comprises two novel tandemly repeated kinked 3-helix bundle domains that structure-based alignments identify as key import domains in other pyocins. The central domain binds the lipid-bound common polysaccharide antigen, allowing the pyocin to accumulate on the cell surface. The N-terminal domain binds the ferric pyochelin transporter FptA while its associated disordered region binds the inner membrane protein TonB1, which together drive import of the bacteriocin across the outer membrane. Finally, we identify the minimal requirements for sensitizing Escherichia coli toward PyoS5, as well as other pyocins, and suggest that a generic pathway likely underpins the import of all TonB-dependent bacteriocins across the outer membrane of Gram-negative bacteria.IMPORTANCE Bacteriocins are toxic polypeptides made by bacteria to kill their competitors, making them interesting as potential antibiotics. Here, we reveal unsuspected commonalities in bacteriocin uptake pathways, through molecular and cellular dissection of the import pathway for the pore-forming bacteriocin pyocin S5 (PyoS5), which targets Pseudomonas aeruginosa In addition to its C-terminal pore-forming domain, PyoS5 is composed of two tandemly repeated helical domains that we also identify in other pyocins. Functional analyses demonstrate that they have distinct roles in the import process. One recognizes conserved sugars projected from the surface, while the other recognizes a specific outer membrane siderophore transporter, FptA, in the case of PyoS5. Through engineering of Escherichia coli cells, we show that pyocins can be readily repurposed to kill other species. This suggests basic ground rules for the outer membrane translocation step that likely apply to many bacteriocins targeting Gram-negative bacteria.
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Affiliation(s)
- Hannah M Behrens
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Edward D Lowe
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Joseph Gault
- Chemistry Research Laboratory, University of Oxford, Oxford, United Kingdom
| | - Nicholas G Housden
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Renata Kaminska
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - T Moritz Weber
- Institute of Bioorganic Chemistry, Heinrich Heine University Düsseldorf, Forschungszentrum Jülich, Jülich, Germany
| | - Catriona M A Thompson
- Institute of Infection, Immunity, and Inflammation, College of Medical, Veterinary, and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Gaëtan L A Mislin
- UMR 7242, Biotechnologie et Signalisation Cellulaire, ESBS, Illkirch, France
| | - Isabelle J Schalk
- UMR 7242, Biotechnologie et Signalisation Cellulaire, ESBS, Illkirch, France
| | - Daniel Walker
- Institute of Infection, Immunity, and Inflammation, College of Medical, Veterinary, and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Carol V Robinson
- Chemistry Research Laboratory, University of Oxford, Oxford, United Kingdom
| | - Colin Kleanthous
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
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15
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Atanaskovic I, Kleanthous C. Tools and Approaches for Dissecting Protein Bacteriocin Import in Gram-Negative Bacteria. Front Microbiol 2019; 10:646. [PMID: 31001227 PMCID: PMC6455109 DOI: 10.3389/fmicb.2019.00646] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Accepted: 03/14/2019] [Indexed: 12/30/2022] Open
Abstract
Bacteriocins of Gram-negative bacteria are typically multi-domain proteins that target and kill bacteria of the same or closely related species. There is increasing interest in protein bacteriocin import; from a fundamental perspective to understand how folded proteins are imported into bacteria and from an applications perspective as species-specific antibiotics to combat multidrug resistant bacteria. In order to translocate across the cell envelope and cause cell death, protein bacteriocins hijack nutrient uptake pathways. Their import is energized by parasitizing intermembrane protein complexes coupled to the proton motive force, which delivers a toxic domain into the cell. A plethora of genetic, structural, biochemical, and biophysical methods have been applied to find cell envelope components involved in bacteriocin import since their discovery almost a century ago. Here, we review the various approaches that now exist for investigating how protein bacteriocins translocate into Gram-negative bacteria and highlight areas of research that will need methodological innovations to fully understand this process. We also highlight recent studies demonstrating how bacteriocins can be used to probe organization and architecture of the Gram-negative cell envelope itself.
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Affiliation(s)
| | - Colin Kleanthous
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
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16
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Sharp C, Boinett C, Cain A, Housden NG, Kumar S, Turner K, Parkhill J, Kleanthous C. O-Antigen-Dependent Colicin Insensitivity of Uropathogenic Escherichia coli. J Bacteriol 2019; 201:e00545-18. [PMID: 30510143 PMCID: PMC6351738 DOI: 10.1128/jb.00545-18] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Accepted: 11/05/2018] [Indexed: 11/20/2022] Open
Abstract
The outer membrane of Gram-negative bacteria presents a significant barrier for molecules entering the cell. Nevertheless, colicins, which are antimicrobial proteins secreted by Escherichia coli, can target other E. coli cells by binding to cell surface receptor proteins and activating their import, resulting in cell death. Previous studies have documented high rates of nonspecific resistance (insensitivity) of various E. coli strains toward colicins that is independent of colicin-specific immunity and is instead associated with lipopolysaccharide (LPS) in the outer membrane. This observation poses a contradiction: why do E. coli strains have colicin-expressing plasmids, which are energetically costly to retain, if cells around them are likely to be naturally insensitive to the colicin they produce? Here, using a combination of transposon sequencing and phenotypic microarrays, we show that colicin insensitivity of uropathogenic E. coli sequence type 131 (ST131) is dependent on the production of its O-antigen but that minor changes in growth conditions render the organism sensitive toward colicins. The reintroduction of O-antigen into E. coli K-12 demonstrated that it is the density of O-antigen that is the dominant factor governing colicin insensitivity. We also show, by microscopy of fluorescently labelled colicins, that growth conditions affect the degree of occlusion by O-antigen of outer membrane receptors but not the clustered organization of receptors. The result of our study demonstrate that environmental conditions play a critical role in sensitizing E. coli toward colicins and that O-antigen in LPS is central to this role.IMPORTANCEEscherichia coli infections can be a major health burden, especially with the organism becoming increasingly resistant to "last-resort" antibiotics such as carbapenems. Although colicins are potent narrow-spectrum antimicrobials with potential as future antibiotics, high levels of naturally occurring colicin insensitivity have been documented which could limit their efficacy. We identify O-antigen-dependent colicin insensitivity in a clinically relevant uropathogenic E. coli strain and show that this insensitivity can be circumvented by minor changes to growth conditions. The results of our study suggest that colicin insensitivity among E. coli organisms has been greatly overestimated, and as a consequence, colicins could in fact be effective species-specific antimicrobials targeting pathogenic E. coli such as uropathogenic E. coli (UPEC).
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Affiliation(s)
- Connor Sharp
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | | | - Amy Cain
- Wellcome Sanger Institute, Hinxton, United Kingdom
- Macquarie University, Sydney, Australia
| | - Nicholas G Housden
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Sandip Kumar
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Keith Turner
- Quadram Institute Bioscience, Norwich, United Kingdom
| | | | - Colin Kleanthous
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
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17
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Duché D, Houot L. Similarities and Differences between Colicin and Filamentous Phage Uptake by Bacterial Cells. EcoSal Plus 2019; 8. [PMID: 30681066 DOI: 10.1128/ecosalplus.esp-0030-2018] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Indexed: 06/09/2023]
Abstract
Gram-negative bacteria have evolved a complex envelope to adapt and survive in a broad range of ecological niches. This physical barrier is the first line of defense against noxious compounds and viral particles called bacteriophages. Colicins are a family of bactericidal proteins produced by and toxic to Escherichia coli and closely related bacteria. Filamentous phages have a complex structure, composed of at least five capsid proteins assembled in a long thread-shaped particle, that protects the viral DNA. Despite their difference in size and complexity, group A colicins and filamentous phages both parasitize multiprotein complexes of their sensitive host for entry. They first bind to a receptor located at the surface of the target bacteria before specifically recruiting components of the Tol system to cross the outer membrane and find their way through the periplasm. The Tol system is thought to use the proton motive force of the inner membrane to maintain outer membrane integrity during the life cycle of the cell. This review describes the sequential docking mechanisms of group A colicins and filamentous phages during their uptake by their bacterial host, with a specific focus on the translocation step, promoted by interactions with the Tol system.
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Affiliation(s)
- Denis Duché
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires, UMR7255, Institut de Microbiologie de la Méditerranée, Aix-Marseille Université-CNRS, 13402 Marseille, France
| | - Laetitia Houot
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires, UMR7255, Institut de Microbiologie de la Méditerranée, Aix-Marseille Université- CNRS, 13402 Marseille, France
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18
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On mechanisms of colicin import: the outer membrane quandary. Biochem J 2018; 475:3903-3915. [PMID: 30541793 DOI: 10.1042/bcj20180477] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Revised: 11/02/2018] [Accepted: 11/12/2018] [Indexed: 01/09/2023]
Abstract
Current problems in the understanding of colicin import across the Escherichia coli outer membrane (OM), involving a range of cytotoxic mechanisms, are discussed: (I) Crystal structure analysis of colicin E3 (RNAase) with bound OM vitamin B12 receptor, BtuB, and of the N-terminal translocation (T) domain of E3 and E9 (DNAase) inserted into the OM OmpF porin, provide details of the initial interaction of the colicin central receptor (R)- and N-terminal T-domain with OM receptors/translocators. (II) Features of the translocon include: (a) high-affinity (K d ≈ 10-9 M) binding of the E3 receptor-binding R-domain E3 to BtuB; (b) insertion of disordered colicin N-terminal domain into the OmpF trimer; (c) binding of the N-terminus, documented for colicin E9, to the TolB protein on the periplasmic side of OmpF. Reinsertion of the colicin N-terminus into the second of the three pores in OmpF implies a colicin anchor site on the periplasmic side of OmpF. (III) Studies on the insertion of nuclease colicins into the cytoplasmic compartment imply that translocation proceeds via the C-terminal catalytic domain, proposed here to insert through the unoccupied third pore of the OmpF trimer, consistent with in vitro occlusion of OmpF channels by the isolated E3 C-terminal domain. (IV) Discussion of channel-forming colicins focuses mainly on colicin E1 for which BtuB is receptor and the OM TolC protein the proposed translocator. The ability of TolC, part of a multidrug efflux pump, for which there is no precedent for an import function, to provide a trans-periplasmic import pathway for colicin E1, is questioned on the basis of an unfavorable hairpin conformation of colicin N-terminal peptides inserted into TolC.
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19
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Gutiérrez-del-Río I, Marín L, Fernández J, Álvarez San Millán M, Ferrero FJ, Valledor M, Campo JC, Cobián N, Méndez I, Lombó F. Development of a biosensor protein bullet as a fluorescent method for fast detection of Escherichia coli in drinking water. PLoS One 2018; 13:e0184277. [PMID: 29304041 PMCID: PMC5755745 DOI: 10.1371/journal.pone.0184277] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Accepted: 08/21/2017] [Indexed: 11/23/2022] Open
Abstract
Drinking water can be exposed to different biological contaminants from the source, through the pipelines, until reaching the final consumer or industry. Some of these are pathogenic bacteria and viruses which may cause important gastrointestinal or systemic diseases. The microbiological quality of drinking water relies mainly in monitoring three indicator bacteria of faecal origin, Escherichia coli, Enterococcus faecalis and Clostridium perfringens, which serve as early sentinels of potential health hazards for the population. Here we describe the analysis of three chimeric fluorescent protein bullets as biosensor candidates for fast detection of E. coli in drinking water. Two of the chimeric proteins (based on GFP-hadrurin and GFP-pb5 chimera proteins) failed with respect to specificity and/or sensitivity, but the GFP-colS4 chimera protein was able to carry out specific detection of E. coli in drinking water samples in a procedure encompassing about 8 min for final result and this biosensor protein was able to detect in a linear way between 20 and 103 CFU of this bacterium. Below 20 CFU, the system cannot differentiate presence or absence of the target bacterium. The fluorescence in this biosensor system is provided by the GFP subunit of the chimeric protein, which, in the case of the better performing sensor bullet, GFP-colS4 chimera, is covalently bound to a flexible peptide bridge and to a bacteriocin binding specifically to E. coli cells. Once bound to the target bacteria, the excitation step with 395 nm LED light causes emission of fluorescence from the GFP domain, which is amplified in a photomultiplier tube, and finally this signal is converted into an output voltage which can be associated with a CFU value and these data distributed along mobile phone networks, for example. This method, and the portable fluorimeter which has been developed for it, may contribute to reduce the analysis time for detecting E. coli presence in drinking water.
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Affiliation(s)
- Ignacio Gutiérrez-del-Río
- Research Group BIONUC, Departamento de Biología Funcional, Área de Microbiología, University of Oviedo, Oviedo, Principality of Asturias, Spain
| | - Laura Marín
- Research Group BIONUC, Departamento de Biología Funcional, Área de Microbiología, University of Oviedo, Oviedo, Principality of Asturias, Spain
| | - Javier Fernández
- Research Group BIONUC, Departamento de Biología Funcional, Área de Microbiología, University of Oviedo, Oviedo, Principality of Asturias, Spain
| | - María Álvarez San Millán
- Research Group BIONUC, Departamento de Biología Funcional, Área de Microbiología, University of Oviedo, Oviedo, Principality of Asturias, Spain
| | - Francisco Javier Ferrero
- Department of Electric, Electronic, Computer and Systems Engineering, University of Oviedo, Campus of Gijón, Gijón, Principality of Asturias, Spain
| | - Marta Valledor
- Department of Electric, Electronic, Computer and Systems Engineering, University of Oviedo, Campus of Gijón, Gijón, Principality of Asturias, Spain
| | - Juan Carlos Campo
- Department of Electric, Electronic, Computer and Systems Engineering, University of Oviedo, Campus of Gijón, Gijón, Principality of Asturias, Spain
| | | | | | - Felipe Lombó
- Research Group BIONUC, Departamento de Biología Funcional, Área de Microbiología, University of Oviedo, Oviedo, Principality of Asturias, Spain
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20
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Johnson CL, Solovyova AS, Hecht O, Macdonald C, Waller H, Grossmann JG, Moore GR, Lakey JH. The Two-State Prehensile Tail of the Antibacterial Toxin Colicin N. Biophys J 2017; 113:1673-1684. [PMID: 29045862 PMCID: PMC5647543 DOI: 10.1016/j.bpj.2017.08.030] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Revised: 07/26/2017] [Accepted: 08/02/2017] [Indexed: 12/16/2022] Open
Abstract
Intrinsically disordered regions within proteins are critical elements in many biomolecular interactions and signaling pathways. Antibacterial toxins of the colicin family, which could provide new antibiotic functions against resistant bacteria, contain disordered N-terminal translocation domains (T-domains) that are essential for receptor binding and the penetration of the Escherichia coli outer membrane. Here we investigate the conformational behavior of the T-domain of colicin N (ColN-T) to understand why such domains are widespread in toxins that target Gram-negative bacteria. Like some other intrinsically disordered proteins in the solution state of the protein, ColN-T shows dual recognition, initially interacting with other domains of the same colicin N molecule and later, during cell killing, binding to two different receptors, OmpF and TolA, in the target bacterium. ColN-T is invisible in the high-resolution x-ray model and yet accounts for 90 of the toxin's 387 amino acid residues. To reveal its solution structure that underlies such a dynamic and complex system, we carried out mutagenic, biochemical, hydrodynamic and structural studies using analytical ultracentrifugation, NMR, and small-angle x-ray scattering on full-length ColN and its fragments. The structure was accurately modeled from small-angle x-ray scattering data by treating ColN as a flexible system, namely by the ensemble optimization method, which enables a distribution of conformations to be included in the final model. The results reveal, to our knowledge, for the first time the dynamic structure of a colicin T-domain. ColN-T is in dynamic equilibrium between a compact form, showing specific self-recognition and resistance to proteolysis, and an extended form, which most likely allows for effective receptor binding.
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Affiliation(s)
- Christopher L Johnson
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Alexandra S Solovyova
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom.
| | - Olli Hecht
- Centre for Structural and Molecular Biology, School of Chemistry, University of East Anglia, Norwich, United Kingdom
| | - Colin Macdonald
- Centre for Structural and Molecular Biology, School of Chemistry, University of East Anglia, Norwich, United Kingdom
| | - Helen Waller
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - J Günter Grossmann
- Institute of Integrative Biology, Structural and Chemical Biology, Liverpool, United Kingdom
| | - Geoffrey R Moore
- Centre for Structural and Molecular Biology, School of Chemistry, University of East Anglia, Norwich, United Kingdom
| | - Jeremy H Lakey
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom
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21
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Structural and biophysical analysis of nuclease protein antibiotics. Biochem J 2016; 473:2799-812. [PMID: 27402794 PMCID: PMC5264503 DOI: 10.1042/bcj20160544] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Accepted: 07/07/2016] [Indexed: 01/28/2023]
Abstract
Protein antibiotics (bacteriocins) are a large and diverse family of multidomain toxins that kill specific Gram-negative bacteria during intraspecies competition for resources. Our understanding of the mechanism of import of such potent toxins has increased significantly in recent years, especially with the reporting of several structures of bacteriocin domains. Less well understood is the structural biochemistry of intact bacteriocins and how these compare across bacterial species. Here, we focus on endonuclease (DNase) bacteriocins that target the genomes of Escherichia coli and Pseudomonas aeruginosa, known as E-type colicins and S-type pyocins, respectively, bound to their specific immunity (Im) proteins. First, we report the 3.2 Å structure of the DNase colicin ColE9 in complex with its ultra-high affinity Im protein, Im9. In contrast with Im3, which when bound to the ribonuclease domain of the homologous colicin ColE3 makes contact with the translocation (T) domain of the toxin, we find that Im9 makes no such contact and only interactions with the ColE9 cytotoxic domain are observed. Second, we report small-angle X-ray scattering data for two S-type DNase pyocins, S2 and AP41, into which are fitted recently determined X-ray structures for isolated domains. We find that DNase pyocins and colicins are both highly elongated molecules, even though the order of their constituent domains differs. We discuss the implications of these architectural similarities and differences in the context of the translocation mechanism of protein antibiotics through the cell envelope of Gram-negative bacteria.
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22
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Burger VM, Nolasco DO, Stultz CM. Expanding the Range of Protein Function at the Far End of the Order-Structure Continuum. J Biol Chem 2016; 291:6706-13. [PMID: 26851282 PMCID: PMC4807258 DOI: 10.1074/jbc.r115.692590] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The traditional view of the structure-function paradigm is that a protein's function is inextricably linked to a well defined, three-dimensional structure, which is determined by the protein's primary amino acid sequence. However, it is now accepted that a number of proteins do not adopt a unique tertiary structure in solution and that some degree of disorder is required for many proteins to perform their prescribed functions. In this review, we highlight how a number of protein functions are facilitated by intrinsic disorder and introduce a new protein structure taxonomy that is based on quantifiable metrics of a protein's disorder.
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Affiliation(s)
- Virginia M Burger
- From the Research Laboratory for Electronics, Department of Electrical Engineering & Computer Science, and
| | - Diego O Nolasco
- From the Research Laboratory for Electronics, Department of Electrical Engineering & Computer Science, and
| | - Collin M Stultz
- From the Research Laboratory for Electronics, Department of Electrical Engineering & Computer Science, and the Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02138
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23
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Abstract
The major class of integral proteins found in the outer membrane (OM) of E. coli and Salmonella adopt a β-barrel conformation (OMPs). OMPs are synthesized in the cytoplasm with a typical signal sequence at the amino terminus, which directs them to the secretion machinery (SecYEG) located in the inner membrane for translocation to the periplasm. Chaperones such as SurA, or DegP and Skp, escort these proteins across the aqueous periplasm protecting them from aggregation. The chaperones then deliver OMPs to a highly conserved outer membrane assembly site termed the Bam complex. In E. coli, the Bam complex is composed of an essential OMP, BamA, and four associated OM lipoproteins, BamBCDE, one of which, BamD, is also essential. Here we provide an overview of what we know about the process of OMP assembly and outline the various hypotheses that have been proposed to explain how proteins might be integrated into the asymmetric OM lipid bilayer in an environment that lacks obvious energy sources. In addition, we describe the envelope stress responses that ensure the fidelity of OM biogenesis and how factors, such as phage and certain toxins, have coopted this essential machine to gain entry into the cell.
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24
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Rassam P, Copeland NA, Birkholz O, Tóth C, Chavent M, Duncan AL, Cross SJ, Housden NG, Kaminska R, Seger U, Quinn DM, Garrod TJ, Sansom MSP, Piehler J, Baumann CG, Kleanthous C. Supramolecular assemblies underpin turnover of outer membrane proteins in bacteria. Nature 2015; 523:333-6. [PMID: 26061769 PMCID: PMC4905513 DOI: 10.1038/nature14461] [Citation(s) in RCA: 143] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Accepted: 04/08/2015] [Indexed: 12/24/2022]
Abstract
Gram-negative bacteria inhabit a broad range of ecological niches. For Escherichia coli, this includes river water as well as humans and animals, where it can be both a commensal and a pathogen. Intricate regulatory mechanisms ensure that bacteria have the right complement of β-barrel outer membrane proteins (OMPs) to enable adaptation to a particular habitat. Yet no mechanism is known for replacing OMPs in the outer membrane, an issue that is further confounded by the lack of an energy source and the high stability and abundance of OMPs. Here we uncover the process underpinning OMP turnover in E. coli and show it to be passive and binary in nature, in which old OMPs are displaced to the poles of growing cells as new OMPs take their place. Using fluorescent colicins as OMP-specific probes, in combination with ensemble and single-molecule fluorescence microscopy in vivo and in vitro, as well as molecular dynamics simulations, we established the mechanism for binary OMP partitioning. OMPs clustered to form ∼0.5-μm diameter islands, where their diffusion is restricted by promiscuous interactions with other OMPs. OMP islands were distributed throughout the cell and contained the Bam complex, which catalyses the insertion of OMPs in the outer membrane. However, OMP biogenesis occurred as a gradient that was highest at mid-cell but largely absent at cell poles. The cumulative effect is to push old OMP islands towards the poles of growing cells, leading to a binary distribution when cells divide. Hence, the outer membrane of a Gram-negative bacterium is a spatially and temporally organized structure, and this organization lies at the heart of how OMPs are turned over in the membrane.
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Affiliation(s)
- Patrice Rassam
- 1] Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK [2] Department of Biology, University of York, York YO10 5DD, UK
| | | | - Oliver Birkholz
- Department of Biology, University of Osnabrück, Barbarastraße 11, 49076 Osnabrück, Germany
| | - Csaba Tóth
- Department of Biology, University of York, York YO10 5DD, UK
| | - Matthieu Chavent
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Anna L Duncan
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Stephen J Cross
- Department of Biology, University of York, York YO10 5DD, UK
| | - Nicholas G Housden
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Renata Kaminska
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Urban Seger
- Department of Biology, University of York, York YO10 5DD, UK
| | - Diana M Quinn
- Department of Biology, University of York, York YO10 5DD, UK
| | - Tamsin J Garrod
- Department of Biology, University of York, York YO10 5DD, UK
| | - Mark S P Sansom
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Jacob Piehler
- Department of Biology, University of Osnabrück, Barbarastraße 11, 49076 Osnabrück, Germany
| | | | - Colin Kleanthous
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
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25
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Konovalova A, Perlman DH, Cowles CE, Silhavy TJ. Transmembrane domain of surface-exposed outer membrane lipoprotein RcsF is threaded through the lumen of β-barrel proteins. Proc Natl Acad Sci U S A 2014; 111:E4350-8. [PMID: 25267629 PMCID: PMC4205638 DOI: 10.1073/pnas.1417138111] [Citation(s) in RCA: 93] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
RcsF (regulator of capsule synthesis) is an outer membrane (OM) lipoprotein that functions to sense defects such as changes in LPS. However, LPS is found in the outer leaflet, and RcsF was thought to be tethered to the inner leaflet by its lipidated N terminus, raising the question of how it monitors LPS. We show that RcsF has a transmembrane topology with the lipidated N terminus on the cell surface and the C-terminal signaling domain in the periplasm. Strikingly, the short, unstructured, charged transmembrane domain is threaded through the lumen of β-barrel OM proteins where it is protected from the hydrophobic membrane interior. We present evidence that these unusual complexes, which contain one protein inside another, are formed by the Bam complex that assembles all β-barrel proteins in the OM. The ability of the Bam complex to expose lipoproteins at the cell surface underscores the mechanistic versatility of the β-barrel assembly machine.
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Affiliation(s)
- Anna Konovalova
- Department of Molecular Biology, Lewis Thomas Laboratory, Princeton University, Princeton, NJ 08544
| | - David H Perlman
- Department of Molecular Biology, Lewis Thomas Laboratory, Princeton University, Princeton, NJ 08544
| | - Charles E Cowles
- Department of Molecular Biology, Lewis Thomas Laboratory, Princeton University, Princeton, NJ 08544
| | - Thomas J Silhavy
- Department of Molecular Biology, Lewis Thomas Laboratory, Princeton University, Princeton, NJ 08544
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26
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Mora L, de Zamaroczy M. In vivo processing of DNase colicins E2 and E7 is required for their import into the cytoplasm of target cells. PLoS One 2014; 9:e96549. [PMID: 24840776 PMCID: PMC4026351 DOI: 10.1371/journal.pone.0096549] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2014] [Accepted: 04/08/2014] [Indexed: 11/19/2022] Open
Abstract
DNase colicins E2 and E7, both of which appropriate the BtuB/Tol translocation machinery to cross the outer membrane, undergo a processing step as they enter the cytoplasm. This endoproteolytic cleavage is essential for their killing action. A processed form of the same size, 18.5 kDa, which corresponds to the C-terminal catalytic domain, was detected in the cytoplasm of bacteria treated with either of the two DNase colicins. The inner-membrane protease FtsH is necessary for the processing that allows the translocation of the colicin DNase domain into the cytoplasm. The processing occurs near residue D420, at the same position as the FtsH-dependent cleavage in RNase colicins E3 and D. The cleavage site is located 30 amino acids upstream of the DNase domain. In contrast, the previously reported periplasm-dependent colicin cleavage, located at R452 in colicin E2, was shown to be generated by the outer-membrane protease OmpT and we show that this cleavage is not physiologically relevant for colicin import. Residue R452, whose mutated derivatives led to toxicity defect, was shown to have no role in colicin processing and translocation, but it plays a key role in the catalytic activity, as previously reported for other DNase colicins. Membrane associated forms of colicins E2 and E7 were detected on target cells as proteinase K resistant peptides, which include both the receptor-binding and DNase domains. A similar, but much less proteinase K-resistant form was also detected with RNase colicin E3. These colicin forms are not relevant for colicin import, but their detection on the cell surface indicates that whole nuclease-colicin molecules are found in a stable association with the outer-membrane receptor BtuB of the target cells.
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Affiliation(s)
- Liliana Mora
- Institut de Biologie Physico-Chimique, CNRS, UPR 9073, Paris, France
| | - Miklos de Zamaroczy
- Institut de Biologie Physico-Chimique, CNRS, UPR 9073, Paris, France
- * E-mail:
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27
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Kim YC, Tarr AW, Penfold CN. Colicin import into E. coli cells: a model system for insights into the import mechanisms of bacteriocins. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:1717-31. [PMID: 24746518 DOI: 10.1016/j.bbamcr.2014.04.010] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Revised: 04/04/2014] [Accepted: 04/06/2014] [Indexed: 01/03/2023]
Abstract
Bacteriocins are a diverse group of ribosomally synthesized protein antibiotics produced by most bacteria. They range from small lanthipeptides produced by lactic acid bacteria to much larger multi domain proteins of Gram negative bacteria such as the colicins from Escherichia coli. For activity bacteriocins must be released from the producing cell and then bind to the surface of a sensitive cell to instigate the import process leading to cell death. For over 50years, colicins have provided a working platform for elucidating the structure/function studies of bacteriocin import and modes of action. An understanding of the processes that contribute to the delivery of a colicin molecule across two lipid membranes of the cell envelope has advanced our knowledge of protein-protein interactions (PPI), protein-lipid interactions and the role of order-disorder transitions of protein domains pertinent to protein transport. In this review, we provide an overview of the arrangement of genes that controls the synthesis and release of the mature protein. We examine the uptake processes of colicins from initial binding and sequestration of binding partners to crossing of the outer membrane, and then discuss the translocation of colicins through the cell periplasm and across the inner membrane to their cytotoxic site of action. This article is part of a Special Issue entitled: Protein trafficking and secretion in bacteria. Guest Editors: Anastassios Economou and Ross Dalbey.
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Affiliation(s)
- Young Chan Kim
- School of Life Sciences, University of Nottingham, Queens Medical Centre, Nottingham, NG7 2UH, UK
| | - Alexander W Tarr
- School of Life Sciences, University of Nottingham, Queens Medical Centre, Nottingham, NG7 2UH, UK
| | - Christopher N Penfold
- School of Life Sciences, University of Nottingham, Queens Medical Centre, Nottingham, NG7 2UH, UK.
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28
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Johnson CL, Ridley H, Marchetti R, Silipo A, Griffin DC, Crawford L, Bonev B, Molinaro A, Lakey JH. The antibacterial toxin colicin N binds to the inner core of lipopolysaccharide and close to its translocator protein. Mol Microbiol 2014; 92:440-52. [PMID: 24589252 PMCID: PMC4114557 DOI: 10.1111/mmi.12568] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/27/2014] [Indexed: 12/03/2022]
Abstract
Colicins are a diverse family of large antibacterial protein toxins, secreted by and active against Escherichia coli and must cross their target cell's outer membrane barrier to kill. To achieve this, most colicins require an abundant porin (e.g. OmpF) plus a low‐copy‐number, high‐affinity, outer membrane protein receptor (e.g. BtuB). Recently, genetic screens have suggested that colicin N (ColN), which has no high‐affinity receptor, targets highly abundant lipopolysaccharide (LPS) instead. Here we reveal the details of this interaction and demonstrate that the ColN receptor‐binding domain (ColN‐R) binds to a specific region of LPS close to the membrane surface. Data from in vitro studies using calorimetry and both liquid‐ and solid‐state NMR reveal the interactions behind the in vivo requirement for a defined oligosaccharide region of LPS. Delipidated LPS (LPSΔLIPID) shows weaker binding; and thus full affinity requires the lipid component. The site of LPS binding means that ColN will preferably bind at the interface and thus position itself close to the surface of its translocon component, OmpF. ColN is, currently, unique among colicins in requiring LPS and, combined with previous data, this implies that the ColN translocon is distinct from those of other known colicins.
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Affiliation(s)
- Christopher L Johnson
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Faculty of Medical Sciences, Newcastle University, Framlington Place, Newcastle-upon-Tyne, NE2 4HH, UK
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29
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Ando T, Uchihashi T, Scheuring S. Filming biomolecular processes by high-speed atomic force microscopy. Chem Rev 2014; 114:3120-88. [PMID: 24476364 PMCID: PMC4076042 DOI: 10.1021/cr4003837] [Citation(s) in RCA: 231] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Indexed: 12/21/2022]
Affiliation(s)
- Toshio Ando
- Department of Physics, and Bio-AFM Frontier
Research Center, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
- CREST,
Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi 332-0012, Japan
| | - Takayuki Uchihashi
- Department of Physics, and Bio-AFM Frontier
Research Center, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
- CREST,
Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi 332-0012, Japan
| | - Simon Scheuring
- U1006
INSERM/Aix-Marseille Université, Parc Scientifique et Technologique
de Luminy Bâtiment Inserm TPR2 bloc 5, 163 avenue de Luminy, 13288 Marseille Cedex 9, France
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30
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Jakes KS. Daring to be different: colicin N finds another way. Mol Microbiol 2014; 92:435-9. [PMID: 24589284 DOI: 10.1111/mmi.12569] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/27/2014] [Indexed: 11/28/2022]
Abstract
The mechanisms by which colicins, protein toxins produced by Escherichia coli, kill other E. coli, have become much better understood in recent years. Most colicins initially bind to an outer membrane protein receptor, and then search for a separate nearby outer membrane protein translocator that serves as a pathway into target cells. Many colicins use the outer membrane porin, OmpF, as that translocator, while using a different primary receptor. Colicin N is unique among known colicins in that only OmpF had been identified as being required for uptake of the colicin and it was presumed to somehow serve as both receptor and translocator. Genetic screens also identified a number of genes required for lipopolysaccharide (LPS) synthesis as uniquely required for killing by colicin N, but not by other colicins. Johnson et al. show that the receptor-binding domain of colicin N binds to LPS, and does not require OmpF for that binding. LPS of a minimal length is required for binding, explaining the requirement for specific elements of the LPS biosynthetic pathway. For colicin N, the receptor-binding domain does not recognize a protein, but rather the most abundant component of the outer membrane itself, LPS.
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Affiliation(s)
- Karen S Jakes
- Department of Physiology and Biophysics, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY, 10461, USA
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31
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Vankemmelbeke M, Housden NG, James R, Kleanthous C, Penfold CN. Immunity protein release from a cell-bound nuclease colicin complex requires global conformational rearrangement. Microbiologyopen 2013; 2:853-61. [PMID: 24039240 PMCID: PMC3831645 DOI: 10.1002/mbo3.122] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2013] [Revised: 07/12/2013] [Accepted: 07/21/2013] [Indexed: 11/24/2022] Open
Abstract
Nuclease colicins bind their target receptor BtuB in the outer membrane of sensitive Escherichia coli cells in the form of a high-affinity complex with their cognate immunity proteins. The release of the immunity protein from the colicin complex is a prerequisite for cell entry of the colicin and occurs via a process that is still relatively poorly understood. We have previously shown that an energy input in the form of the cytoplasmic membrane proton motive force is required to promote immunity protein (Im9) release from the colicin E9/Im9 complex and colicin cell entry. We report here that engineering rigidity in the structured part of the colicin translocation domain via the introduction of disulfide bonds prevents immunity protein release from the colicin complex. Reduction of the disulfide bond by the addition of DTT leads to immunity protein release and resumption of activity. Similarly, the introduction of a disulfide bond in the DNase domain previously shown to abolish channel formation in planar bilayers also prevented immunity protein release. Importantly, all disulfide bonds, in the translocation as well as the DNase domain, also abolished the biological activity of the Im9-free colicin E9, the reduction of which led to a resumption of activity. Our results show, for the first time, that conformational flexibility in the structured translocation and DNase domains of a nuclease colicin is essential for immunity protein release, providing further evidence for the hypothesis that global structural rearrangement of the colicin molecule is required for disassembly of this high-affinity toxin-immunity protein complex prior to outer membrane translocation.
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Affiliation(s)
- Mireille Vankemmelbeke
- School of Life Sciences, Centre for Biomolecular Sciences, University of Nottingham, University Park, Nottingham, NG7 2RD, United Kingdom
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32
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Housden NG, Hopper JT, Lukoyanova N, Rodriguez-Larrea D, Wojdyla JA, Klein A, Kaminska R, Bayley H, Saibil HR, Robinson CV, Kleanthous C. Intrinsically disordered protein threads through the bacterial outer-membrane porin OmpF. Science 2013; 340:1570-4. [PMID: 23812713 PMCID: PMC3856478 DOI: 10.1126/science.1237864] [Citation(s) in RCA: 104] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Porins are β-barrel outer-membrane proteins through which small solutes and metabolites diffuse that are also exploited during cell death. We have studied how the bacteriocin colicin E9 (ColE9) assembles a cytotoxic translocon at the surface of Escherichia coli that incorporates the trimeric porin OmpF. Formation of the translocon involved ColE9's unstructured N-terminal domain threading in opposite directions through two OmpF subunits, capturing its target TolB on the other side of the membrane in a fixed orientation that triggers colicin import. Thus, an intrinsically disordered protein can tunnel through the narrow pores of an oligomeric porin to deliver an epitope signal to the cell to initiate cell death.
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Affiliation(s)
- Nicholas G. Housden
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Jonathan T.S. Hopper
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, UK
| | - Natalya Lukoyanova
- Department of Crystallography and Institute of Structural Molecular Biology, Birkbeck College, Malet Street, London WC1E 7HX, UK
| | - David Rodriguez-Larrea
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, UK
| | - Justyna A. Wojdyla
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Alexander Klein
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Renata Kaminska
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Hagan Bayley
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, UK
| | - Helen R. Saibil
- Department of Crystallography and Institute of Structural Molecular Biology, Birkbeck College, Malet Street, London WC1E 7HX, UK
| | - Carol V. Robinson
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, UK
| | - Colin Kleanthous
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
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33
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Rajarathnam K, Rösgen J. Isothermal titration calorimetry of membrane proteins - progress and challenges. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1838:69-77. [PMID: 23747362 DOI: 10.1016/j.bbamem.2013.05.023] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Revised: 05/16/2013] [Accepted: 05/20/2013] [Indexed: 11/20/2022]
Abstract
Integral membrane proteins, including G protein-coupled receptors (GPCR) and ion channels, mediate diverse biological functions that are crucial to all aspects of life. The knowledge of the molecular mechanisms, and in particular, the thermodynamic basis of the binding interactions of the extracellular ligands and intracellular effector proteins is essential to understand the workings of these remarkable nanomachines. In this review, we describe how isothermal titration calorimetry (ITC) can be effectively used to gain valuable insights into the thermodynamic signatures (enthalpy, entropy, affinity, and stoichiometry), which would be most useful for drug discovery studies, considering that more than 30% of the current drugs target membrane proteins. This article is part of a Special Issue entitled: Structural and biophysical characterisation of membrane protein-ligand binding.
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Affiliation(s)
- Krishna Rajarathnam
- Department of Biochemistry and Molecular Biology, The University of Texas Medical Branch, Galveston, TX 77555, USA; Sealy Center for Structural Biology and Molecular Biophysics, The University of Texas Medical Branch, Galveston, TX 77555, USA.
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34
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Johnson CL, Ridley H, Pengelly RJ, Salleh MZ, Lakey JH. The unstructured domain of colicin N kills Escherichia coli. Mol Microbiol 2013; 89:84-95. [PMID: 23672584 PMCID: PMC3739937 DOI: 10.1111/mmi.12260] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/10/2013] [Indexed: 11/28/2022]
Abstract
Bacteria often produce toxins which kill competing bacteria. Colicins, produced by and toxic to Escherichia coli bacteria are three-domain proteins so efficient that one molecule can kill a cell. The C-terminal domain carries the lethal activity and the central domain is required for surface receptor binding. The N-terminal domain, required for translocation across the outer membrane, is always intrinsically unstructured. It has always been assumed therefore that the C-terminal cytotoxic domain is required for the bactericidal activity. Here we report the unexpected finding that in isolation, the 90-residue unstructured N-terminal domain of colicin N is cytotoxic. Furthermore it causes ion leakage from cells but, unlike known antimicrobial peptides (AMPs) with this property, shows no membrane binding behaviour. Finally, its activity remains strictly dependent upon the same receptor proteins (OmpF and TolA) used by full-length colicin N. This mechanism of rapid membrane disruption, via receptor mediated binding of a soluble peptide, may reveal a new target for the development of highly specific antibacterials.
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Affiliation(s)
- Christopher L Johnson
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Faculty of Medical Sciences, Newcastle University, Framlington Place, Newcastle- upon-Tyne, NE2 4HH, UK
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35
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Farrance OE, Hann E, Kaminska R, Housden NG, Derrington SR, Kleanthous C, Radford SE, Brockwell DJ. A force-activated trip switch triggers rapid dissociation of a colicin from its immunity protein. PLoS Biol 2013; 11:e1001489. [PMID: 23431269 PMCID: PMC3576412 DOI: 10.1371/journal.pbio.1001489] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2012] [Accepted: 01/09/2013] [Indexed: 01/24/2023] Open
Abstract
A single-molecule force study shows that rapid dissociation of a high-affinity protein interaction can be triggered by site-specific remodelling of one protein partner, and that prevention of remodelling maintains avidity. Colicins are protein antibiotics synthesised by Escherichia coli strains to target and kill related bacteria. To prevent host suicide, colicins are inactivated by binding to immunity proteins. Despite their high avidity (Kd≈fM, lifetime ≈4 days), immunity protein release is a pre-requisite of colicin intoxication, which occurs on a timescale of minutes. Here, by measuring the dynamic force spectrum of the dissociation of the DNase domain of colicin E9 (E9) and immunity protein 9 (Im9) complex using an atomic force microscope we show that application of low forces (<20 pN) increases the rate of complex dissociation 106-fold, to a timescale (lifetime ≈10 ms) compatible with intoxication. We term this catastrophic force-triggered increase in off-rate a trip bond. Using mutational analysis, we elucidate the mechanism of this switch in affinity. We show that the N-terminal region of E9, which has sparse contacts with the hydrophobic core, is linked to an allosteric activator region in E9 (residues 21–30) whose remodelling triggers immunity protein release. Diversion of the force transduction pathway by the introduction of appropriately positioned disulfide bridges yields a force resistant complex with a lifetime identical to that measured by ensemble techniques. A trip switch within E9 is ideal for its function as it allows bipartite complex affinity, whereby the stable colicin:immunity protein complex required for host protection can be readily converted to a kinetically unstable complex whose dissociation is necessary for cellular invasion and competitor death. More generally, the observation of two force phenotypes for the E9:Im9 complex demonstrates that force can re-sculpt the underlying energy landscape, providing new opportunities to modulate biological reactions in vivo; this rationalises the commonly observed discrepancy between off-rates measured by dynamic force spectroscopy and ensemble methods. Many proteins interact with other proteins as part of their function. One method of modulating the activity of protein complexes is to break them apart. Some complexes, however, are extremely kinetically stable and it is unclear how these can dissociate on a biologically relevant timescale. In this study we address this question using protein complexes between colicin E9 (a bacterial toxin) and its immunity protein Im9. These highly avid complexes (with a lifetime of days) must be broken apart for colicin to be activated. By using single-molecule force methods we show that pulling on one end of colicin E9 drastically destabilises the complex so that it dissociates a million-fold faster than its intrinsic rate. We then show that preventing this destabilisation (by the insertion of cross-links that pin the N-terminus of E9 in place) yields a kinetically stable complex. It has previously been postulated that force can destabilise a protein complex by partially unfolding one or more binding partners. Our work provides new experimental evidence that shows this is the case and provides a mechanism for this phenomenon, which we term a trip bond. For the E9:Im9 complex, trip bond behaviour allows a stable complex to be rapidly dissociated by application of a surprisingly small force.
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Affiliation(s)
- Oliver E. Farrance
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, United Kingdom
- Astbury Centre for Structural Molecular Biology, University of Leeds, United Kingdom
| | - Eleanore Hann
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, United Kingdom
- Astbury Centre for Structural Molecular Biology, University of Leeds, United Kingdom
| | - Renata Kaminska
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | | | - Sasha R. Derrington
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, United Kingdom
- Astbury Centre for Structural Molecular Biology, University of Leeds, United Kingdom
| | - Colin Kleanthous
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Sheena E. Radford
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, United Kingdom
- Astbury Centre for Structural Molecular Biology, University of Leeds, United Kingdom
| | - David J. Brockwell
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, United Kingdom
- Astbury Centre for Structural Molecular Biology, University of Leeds, United Kingdom
- * E-mail:
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Xenocin export by the flagellar type III pathway in Xenorhabdus nematophila. J Bacteriol 2013; 195:1400-10. [PMID: 23335409 DOI: 10.1128/jb.01532-12] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The xenocin operon of Xenorhabdus nematophila consists of xciA and ximB genes encoding a 64-kDa xenocin and 42-kDa immunity protein to kill competing microbes in the insect larva. The catalytic domain of xenocin has RNase activity and is responsible for its cytotoxicity. Under SOS conditions, xenocin is produced with immunity protein as a complex. Here, we show that xenocin and immunity protein complex are exported through the flagellar type III system of X. nematophila. Secretion of xenocin complex was abolished in an flhA strain but not in an fliC strain. The xenocin operon is not linked to the flagellar operon transcriptionally. The immunity protein is produced alone from a second, constitutive promoter and is targeted to the periplasm in a flagellum-independent manner. For stable expression of xenocin, coexpression of immunity protein was necessary. To examine the role of immunity protein in xenocin export, an enzymatically inactive protein was produced by site-directed mutagenesis in the active site of the catalytic domain. Toxicity was abolished in D535A and H538A variants of xenocin, which were expressed alone without an immunity domain and secreted in the culture supernatant through flagellar export. Secretion of xenocin through the flagellar pathway has important implications in the evolutionary success of X. nematophila.
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Affiliation(s)
- Karen S. Jakes
- Department of Physiology and Biophysics, Albert Einstein College of Medicine, Bronx, New York 10461;
| | - William A. Cramer
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907;
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38
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Affiliation(s)
| | - Sergey M. Bezrukov
- Program in Physical Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, U.S.A
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39
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Structural basis of toxicity and immunity in contact-dependent growth inhibition (CDI) systems. Proc Natl Acad Sci U S A 2012; 109:21480-5. [PMID: 23236156 DOI: 10.1073/pnas.1216238110] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Contact-dependent growth inhibition (CDI) systems encode polymorphic toxin/immunity proteins that mediate competition between neighboring bacterial cells. We present crystal structures of CDI toxin/immunity complexes from Escherichia coli EC869 and Burkholderia pseudomallei 1026b. Despite sharing little sequence identity, the toxin domains are structurally similar and have homology to endonucleases. The EC869 toxin is a Zn(2+)-dependent DNase capable of completely degrading the genomes of target cells, whereas the Bp1026b toxin cleaves the aminoacyl acceptor stems of tRNA molecules. Each immunity protein binds and inactivates its cognate toxin in a unique manner. The EC869 toxin/immunity complex is stabilized through an unusual β-augmentation interaction. In contrast, the Bp1026b immunity protein exploits shape and charge complementarity to occlude the toxin active site. These structures represent the initial glimpse into the CDI toxin/immunity network, illustrating how sequence-diverse toxins adopt convergent folds yet retain distinct binding interactions with cognate immunity proteins. Moreover, we present visual demonstration of CDI toxin delivery into a target cell.
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Abstract
We are investigating how protein bacteriocins import their toxic payload across the Gram-negative cell envelope, both as a means of understanding the translocation process itself and as a means of probing the organization of the cell envelope and the function of the protein machines within it. Our work focuses on the import mechanism of the group A endonuclease (DNase) colicin ColE9 into Escherichia coli, where we combine in vivo observations with structural, biochemical and biophysical approaches to dissect the molecular mechanism of colicin entry. ColE9 assembles a multiprotein ‘translocon’ complex at the E. coli outer membrane that triggers entry of the toxin across the outer membrane and the simultaneous jettisoning of its tightly bound immunity protein, Im9, in a step that is dependent on the protonmotive force. In the present paper, we focus on recent work where we have uncovered how ColE9 assembles its translocon complex, including isolation of the complex, and how this leads to subversion of a signal intrinsic to the Tol–Pal assembly within the periplasm and inner membrane. In this way, the externally located ColE9 is able to ‘connect’ to the inner membrane protonmotive force via a network of protein–protein interactions that spans the entirety of the E. coli cell envelope to drive dissociation of Im9 and initiate entry of the colicin into the cell.
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41
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Hijacking cellular functions for processing and delivery of colicins E3 and D into the cytoplasm. Biochem Soc Trans 2012; 40:1486-91. [DOI: 10.1042/bst20120173] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The mechanisms for importing colicins from the extracellular medium into Escherichia coli target cells implicate a complex cascade of interactions with host proteins. It is known that colicins interact with membrane receptors, and they may appropriate them structurally, but not functionally, as a scaffold on the surface of the target cell so that they can be translocated across the outer membrane. During the import into the periplasm, colicins parasitize functionally membrane porins and energy-transducers by mimicking their natural substrates or interacting partners. Such structural or functional parasitism also takes place during the late molecular events responsible for the processing and translocation of nuclease colicins across the inner membrane. Two different RNase colicins (D and E3) require an endoproteolytic cleavage, dependent on the inner membrane ATPase/protease FtsH, in order to transfer their C-terminal toxic domain into the cytoplasm. Moreover, the processing of colicin D necessitates a specific interaction with the signal peptidase LepB, but without appropriating the catalytic activity of this enzyme. A comparison of the differences in structural and functional organizations of these two colicins, as well as the pore-forming colicin B, is discussed in the present paper in connection with the sequential steps of their import mechanisms and the exploitation of the machinery of the target cell.
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42
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Casuso I, Khao J, Chami M, Paul-Gilloteaux P, Husain M, Duneau JP, Stahlberg H, Sturgis JN, Scheuring S. Characterization of the motion of membrane proteins using high-speed atomic force microscopy. NATURE NANOTECHNOLOGY 2012; 7:525-9. [PMID: 22772862 DOI: 10.1038/nnano.2012.109] [Citation(s) in RCA: 116] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Accepted: 06/04/2012] [Indexed: 05/23/2023]
Abstract
For cells to function properly, membrane proteins must be able to diffuse within biological membranes. The functions of these membrane proteins depend on their position and also on protein-protein and protein-lipid interactions. However, so far, it has not been possible to study simultaneously the structure and dynamics of biological membranes. Here, we show that the motion of unlabelled membrane proteins can be characterized using high-speed atomic force microscopy. We find that the molecules of outer membrane protein F (OmpF) are widely distributed in the membrane as a result of diffusion-limited aggregation, and while the overall protein motion scales roughly with the local density of proteins in the membrane, individual protein molecules can also diffuse freely or become trapped by protein-protein interactions. Using these measurements, and the results of molecular dynamics simulations, we determine an interaction potential map and an interaction pathway for a membrane protein, which should provide new insights into the connection between the structures of individual proteins and the structures and dynamics of supramolecular membranes.
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Affiliation(s)
- Ignacio Casuso
- U1006 INSERM, Aix-Marseille Université, Parc Scientifique et Technologique de Luminy, 163 avenue de Luminy, 13009 Marseille, France
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43
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Wöhri AB, Hillertz P, Eriksson PO, Meuller J, Dekker N, Snijder A. Thermodynamic studies of ligand binding to the human homopentameric glycine receptor using isothermal titration calorimetry. Mol Membr Biol 2012; 30:169-83. [DOI: 10.3109/09687688.2012.696733] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Papadakos G, Housden NG, Lilly KJ, Kaminska R, Kleanthous C. Kinetic Basis for the Competitive Recruitment of TolB by the Intrinsically Disordered Translocation Domain of Colicin E9. J Mol Biol 2012; 418:269-80. [DOI: 10.1016/j.jmb.2012.01.039] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2011] [Revised: 01/11/2012] [Accepted: 01/24/2012] [Indexed: 11/15/2022]
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Abstract
It is more than 80 years since Gratia first described 'a remarkable antagonism between two strains of Escherichia coli'. Shown subsequently to be due to the action of proteins (or peptides) produced by one bacterium to kill closely related species with which it might be cohabiting, such bacteriocins have since been shown to be commonplace in the internecine warfare between bacteria. Bacteriocins have been studied primarily from the twin perspectives of how they shape microbial communities and how they penetrate bacteria to kill them. Here, we review the modes of action of a family of bacteriocins that cleave nucleic acid substrates in E. coli, known collectively as nuclease colicins, and the specific immunity (inhibitor) proteins that colicin-producing organisms make in order to avoid committing suicide. In a process akin to targeting in mitochondria, nuclease colicins engage in a variety of cellular associations in order to translocate their cytotoxic domains through the cell envelope to the cytoplasm. As well as informing on the process itself, the study of nuclease colicin import has also illuminated functional aspects of the host proteins they parasitize. We also review recent studies where nuclease colicins and their immunity proteins have been used as model systems for addressing fundamental problems in protein folding and protein-protein interactions, areas of biophysics that are intimately linked to the role of colicins in bacterial competition and to the import process itself.
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Clifton LA, Johnson CL, Solovyova AS, Callow P, Weiss KL, Ridley H, Le Brun AP, Kinane CJ, Webster JRP, Holt SA, Lakey JH. Low resolution structure and dynamics of a colicin-receptor complex determined by neutron scattering. J Biol Chem 2011; 287:337-346. [PMID: 22081604 PMCID: PMC3249085 DOI: 10.1074/jbc.m111.302901] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Proteins that translocate across cell membranes need to overcome a significant hydrophobic barrier. This is usually accomplished via specialized protein complexes, which provide a polar transmembrane pore. Exceptions to this include bacterial toxins, which insert into and cross the lipid bilayer itself. We are studying the mechanism by which large antibacterial proteins enter Escherichia coli via specific outer membrane proteins. Here we describe the use of neutron scattering to investigate the interaction of colicin N with its outer membrane receptor protein OmpF. The positions of lipids, colicin N, and OmpF were separately resolved within complex structures by the use of selective deuteration. Neutron reflectivity showed, in real time, that OmpF mediates the insertion of colicin N into lipid monolayers. This data were complemented by Brewster Angle Microscopy images, which showed a lateral association of OmpF in the presence of colicin N. Small angle neutron scattering experiments then defined the three-dimensional structure of the colicin N-OmpF complex. This revealed that colicin N unfolds and binds to the OmpF-lipid interface. The implications of this unfolding step for colicin translocation across membranes are discussed.
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Affiliation(s)
- Luke A Clifton
- ISIS Spallation Neutron Source, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0QX, United Kingdom
| | - Christopher L Johnson
- Institute for Cell and Molecular Biosciences, The Medical School, University of Newcastle, Framlington Place, Newcastle-upon-Tyne NE2 4HH, United Kingdom
| | - Alexandra S Solovyova
- Institute for Cell and Molecular Biosciences, The Medical School, University of Newcastle, Framlington Place, Newcastle-upon-Tyne NE2 4HH, United Kingdom
| | - Phil Callow
- Partnership for Structural Biology, Institut Laue Langevin, 6 Rue Jules Horowitz, 38042 Grenoble, France
| | - Kevin L Weiss
- Center for Structural Molecular Biology, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831
| | - Helen Ridley
- Institute for Cell and Molecular Biosciences, The Medical School, University of Newcastle, Framlington Place, Newcastle-upon-Tyne NE2 4HH, United Kingdom
| | - Anton P Le Brun
- Institute for Cell and Molecular Biosciences, The Medical School, University of Newcastle, Framlington Place, Newcastle-upon-Tyne NE2 4HH, United Kingdom
| | - Christian J Kinane
- ISIS Spallation Neutron Source, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0QX, United Kingdom
| | - John R P Webster
- ISIS Spallation Neutron Source, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0QX, United Kingdom
| | - Stephen A Holt
- ISIS Spallation Neutron Source, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0QX, United Kingdom
| | - Jeremy H Lakey
- Institute for Cell and Molecular Biosciences, The Medical School, University of Newcastle, Framlington Place, Newcastle-upon-Tyne NE2 4HH, United Kingdom.
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Chauleau M, Mora L, Serba J, de Zamaroczy M. FtsH-dependent processing of RNase colicins D and E3 means that only the cytotoxic domains are imported into the cytoplasm. J Biol Chem 2011; 286:29397-29407. [PMID: 21700705 DOI: 10.1074/jbc.m111.242354] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
It has long been suggested that the import of nuclease colicins requires protein processing; however it had never been formally demonstrated. Here we show that two RNase colicins, E3 and D, which appropriate two different translocation machineries to cross the outer membrane (BtuB/Tol and FepA/TonB, respectively), undergo a processing step inside the cell that is essential to their killing action. We have detected the presence of the C-terminal catalytic domains of these colicins in the cytoplasm of target bacteria. The same processed forms were identified in both colicin-sensitive cells and in cells immune to colicin because of the expression of the cognate immunity protein. We demonstrate that the inner membrane protease FtsH is necessary for the processing of colicins D and E3 during their import. We also show that the signal peptidase LepB interacts directly with the central domain of colicin D in vitro and that it is a specific but not a catalytic requirement for in vivo processing of colicin D. The interaction of colicin D with LepB may ensure a stable association with the inner membrane that in turn allows the colicin recognition by FtsH. We have also shown that the outer membrane protease OmpT is responsible for alternative and distinct endoproteolytic cleavages of colicins D and E3 in vitro, presumably reflecting its known role in the bacterial defense against antimicrobial peptides. Even though the OmpT-catalyzed in vitro cleavage also liberates the catalytic domain from colicins D and E3, it is not involved in the processing of nuclease colicins during their import into the cytoplasm.
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Affiliation(s)
- Mathieu Chauleau
- CNRS, UPR 9073, Institut de Biologie Physico-Chimique, 75005 Paris, France
| | - Liliana Mora
- CNRS, UPR 9073, Institut de Biologie Physico-Chimique, 75005 Paris, France
| | - Justyna Serba
- CNRS, UPR 9073, Institut de Biologie Physico-Chimique, 75005 Paris, France
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48
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Spector J, Zakharov S, Lill Y, Sharma O, Cramer WA, Ritchie K. Mobility of BtuB and OmpF in the Escherichia coli outer membrane: implications for dynamic formation of a translocon complex. Biophys J 2011; 99:3880-6. [PMID: 21156129 DOI: 10.1016/j.bpj.2010.10.029] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2010] [Revised: 10/06/2010] [Accepted: 10/07/2010] [Indexed: 11/18/2022] Open
Abstract
Diffusion of two Escherichia coli outer membrane proteins-the cobalamin (vitamin B12) receptor (BtuB) and the OmpF porin, which are implicated in the cellular import pathways of colicins and phages-was measured in vivo. The lateral mobility of these proteins is relevant to the mechanism of formation of the translocon for cellular import of colicins such as the rRNase colicin E3. The diffusion coefficient (D) of BtuB, the primary colicin receptor, complexed to fluorescent antibody or colicin, is 0.05±0.01 μm2/s and 0.10±0.02 μm2/s, respectively, over a timescale of 25-150 ms. Mutagenesis of the BtuB TonB box, which eliminates or significantly weakens the interaction between BtuB and the TonB energy-transducing protein that is anchored in the cytoplasmic membrane, resulted in a fivefold larger value of D, 0.27±0.06 μm2/s for antibody-labeled BtuB, indicating a cytoskeletal-like interaction of TonB with BtuB. OmpF has a diffusion coefficient of 0.006±0.002 μm2/s, ∼10-fold smaller than that of BtuB, and is restricted within a domain of diameter 100 nm, showing it to be relatively immobile compared to BtuB. Thus, formation of the outer membrane translocon for cellular import of the nuclease colicins is a demonstrably dynamic process, because it depends on lateral diffusion of BtuB and collisional interaction with relatively immobile OmpF.
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Affiliation(s)
- Jeff Spector
- Department of Physics, Purdue University, West Lafayette, Indiana, USA
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50
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Directed epitope delivery across the Escherichia coli outer membrane through the porin OmpF. Proc Natl Acad Sci U S A 2010; 107:21412-7. [PMID: 21098297 DOI: 10.1073/pnas.1010780107] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The porins OmpF and OmpC are trimeric β-barrel proteins with narrow channels running through each monomer that exclude molecules > 600 Da while mediating the passive diffusion of small nutrients and metabolites across the Gram-negative outer membrane (OM). Here, we elucidate the mechanism by which an entire soluble protein domain (> 6 kDa) is delivered through the lumen of such porins. Following high-affinity binding to the vitamin B(12) receptor in Escherichia coli, the bacteriocin ColE9 recruits OmpF or OmpC using an 83-residue intrinsically unstructured translocation domain (IUTD) to deliver a 16-residue TolB-binding epitope (TBE) in the center of the IUTD to the periplasm where it triggers toxin entry. We demonstrate that the IUTD houses two OmpF-binding sites, OBS1 (residues 2-18) and OBS2 (residues 54-63), which flank the TBE and bind with K(d)s of 2 and 24 μM, respectively, at pH 6.5 and 25 ºC. We show the two OBSs share the same binding site on OmpF and that the colicin must house at least one of them for antibiotic activity. Finally, we report the structure of the OmpF-OBS1 complex that shows the colicin bound within the porin lumen spanning the membrane bilayer. Our study explains how colicins exploit porins to deliver epitope signals to the bacterial periplasm and, more broadly, how the inherent flexibility and narrow cross-sectional area of an IUP domain can endow it with the ability to traverse a biological membrane via the constricted lumen of a β-barrel membrane protein.
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