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Jin L, Hu X, Tian Y, Fang M, Dong X, Jiang Y, Han Y, Li H, Sun Y. Detection of Staphylococcus aureus virulence gene pvl based on CRISPR strip. Front Immunol 2024; 15:1345532. [PMID: 38524136 PMCID: PMC10957627 DOI: 10.3389/fimmu.2024.1345532] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Accepted: 02/20/2024] [Indexed: 03/26/2024] Open
Abstract
Introduction Staphylococcus aureus (S. aureus) is a prominent pathogen responsible for both hospital-acquired and community-acquired infections. Among its arsenal of virulence factors, Panton-Valentine Leucocidin (PVL) is closely associated with severe diseases such as profound skin infections and necrotizing pneumonia. Patients infected with pvl-positive S. aureus often exhibit more severe symptoms and carry a substantially higher mortality risk. Therefore, it is crucial to promptly and accurately detect pvl-positive S. aureus before initiating protective measures and providing effective antibacterial treatment. Methods In this study, we propose a precise identification and highly sensitive detection method for pvl-positive S. aureus based on recombinase-assisted amplification and the CRISPR-ERASE strip which we previously developed. Results The results revealed that this method achieved a detection limit of 1 copy/μL for pvl-positive plasmids within 1 hour. The method successfully identified all 25 pvl-positive and 51 pvl-negative strains among the tested 76 isolated S. aureus samples, demonstrating its concordance with qPCR. Discussion These results show that the CRISPR-ERASE detection method for pvl-positive S. aureus has the advantages of high sensitivity and specificity, this method combines the characteristics of recombinase-assisted amplification at room temperature and the advantages of ERASE test strip visualization, which can greatly reduce the dependence on professional laboratories. It is more suitable for on-site detection than PCR and qPCR, thereby providing important value for rapid on-site detection of pvl.
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Affiliation(s)
- Li Jin
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
- College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, Fujian, China
| | - XiaoFeng Hu
- Center for Disease Control and Prevention of Chinese People's Liberation Army, Beijing, China
| | - Yuan Tian
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
| | - MengYa Fang
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
| | - Xue Dong
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
| | - YaXuan Jiang
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
| | - Yao Han
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
| | - Hao Li
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
| | - Yansong Sun
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
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Galenkamp NS, Van Meervelt V, Mutter NL, van der Heide NJ, Wloka C, Maglia G. Preparation of Cytolysin A (ClyA) Nanopores. Methods Mol Biol 2021; 2186:11-18. [PMID: 32918726 DOI: 10.1007/978-1-0716-0806-7_2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The ionic currents passing through nanopores can be used to sequence DNA and identify molecules at the single-molecule level. Recently, researchers have started using nanopores for the detection and analysis of proteins, providing a new platform for single-molecule enzymology studies and more efficient biomolecular sensing applications. For this approach, the homo-oligomeric Cytolysin A (ClyA) nanopore has been demonstrated as a powerful tool. Here, we describe a simple protocol allowing the production of ClyA nanopores. Monomers of ClyA are expressed in Escherichia coli and oligomerized in the presence of detergent. Subsequently, different oligomer variants are electrophoretically resolved and stored in a gel matrix for long-term use.
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Affiliation(s)
- Nicole Stéphanie Galenkamp
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, The Netherlands
| | - Veerle Van Meervelt
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, The Netherlands
| | - Natalie Lisa Mutter
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, The Netherlands
| | - Nieck Jordy van der Heide
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, The Netherlands
| | - Carsten Wloka
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, The Netherlands
| | - Giovanni Maglia
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, The Netherlands.
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Mutter NL, Huang G, van der Heide NJ, Lucas FLR, Galenkamp NS, Maglia G, Wloka C. Preparation of Fragaceatoxin C (FraC) Nanopores. METHODS IN MOLECULAR BIOLOGY (CLIFTON, N.J.) 2020; 2186:3-10. [PMID: 32918725 DOI: 10.1007/978-1-0716-0806-7_1] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Biological nanopores are an emerging class of biosensors with high-end precision owing to their reproducible fabrication at the nanometer scale. Most notably, nanopore-based DNA sequencing applications are currently being commercialized, while nanopore-based proteomics may become a reality in the near future.Although membrane proteins often prove to be difficult to purify, we describe a straightforward protocol for the preparation of Fragaceatoxin C (FraC) nanopores, which may have applications for DNA analysis and nanopore-based proteomics. Recombinantly expressed FraC nanopores are purified via two rounds of Ni-NTA affinity chromatography before and after oligomerization on sphingomyelin-containing liposomes. Starting from a plasmid vector containing the FraC gene, our method allows the production of purified nanopores within a week. Afterward, the FraC nanopores can be stored at +4 °C for several months, or frozen.
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Affiliation(s)
- Natalie Lisa Mutter
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, The Netherlands
| | - Gang Huang
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, The Netherlands
| | - Nieck Jordy van der Heide
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, The Netherlands
| | | | - Nicole Stéphanie Galenkamp
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, The Netherlands
| | - Giovanni Maglia
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, The Netherlands
| | - Carsten Wloka
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, The Netherlands.
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Tan CS, Fleming AM, Ren H, Burrows CJ, White HS. γ-Hemolysin Nanopore Is Sensitive to Guanine-to-Inosine Substitutions in Double-Stranded DNA at the Single-Molecule Level. J Am Chem Soc 2018; 140:14224-14234. [PMID: 30269492 DOI: 10.1021/jacs.8b08153] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Biological nanopores provide a unique single-molecule sensing platform to detect target molecules based on their specific electrical signatures. The γ-hemolysin (γ-HL) protein produced by Staphylococcus aureus is able to assemble into an octamer nanopore with a ∼2.3 nm diameter β-barrel. Herein, we demonstrate the first application of γ-HL nanopore for DNA structural analysis. To optimize conditions for ion-channel recording, the properties of the γ-HL pore (e.g., conductance, voltage-dependent gating, and ion-selectivity) were characterized at different pH, temperature, and electrolyte concentrations. The optimal condition for DNA analysis using γ-HL corresponds to 3 M KCl, pH 5, and T = 20 °C. The γ-HL protein nanopore is able to translocate dsDNA at about ∼20 bp/ms, and the unique current-signature of captured dsDNA can directly distinguish guanine-to-inosine substitutions at the single-molecule level with ∼99% accuracy. The slow dsDNA threading and translocation processes indicate this wild-type γ-HL channel has potential to detect other base modifications in dsDNA.
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Affiliation(s)
- Cherie S Tan
- Department of Chemistry , University of Utah , 315 South 1400 East , Salt Lake City , Utah 84112-0850 , United States
| | - Aaron M Fleming
- Department of Chemistry , University of Utah , 315 South 1400 East , Salt Lake City , Utah 84112-0850 , United States
| | - Hang Ren
- Department of Chemistry , University of Utah , 315 South 1400 East , Salt Lake City , Utah 84112-0850 , United States
| | - Cynthia J Burrows
- Department of Chemistry , University of Utah , 315 South 1400 East , Salt Lake City , Utah 84112-0850 , United States
| | - Henry S White
- Department of Chemistry , University of Utah , 315 South 1400 East , Salt Lake City , Utah 84112-0850 , United States
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Galenkamp NS, Soskine M, Hermans J, Wloka C, Maglia G. Direct electrical quantification of glucose and asparagine from bodily fluids using nanopores. Nat Commun 2018; 9:4085. [PMID: 30291230 PMCID: PMC6173770 DOI: 10.1038/s41467-018-06534-1] [Citation(s) in RCA: 76] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Accepted: 08/30/2018] [Indexed: 01/11/2023] Open
Abstract
Crucial steps in the miniaturisation of biosensors are the conversion of a biological signal into an electrical current as well as the direct sampling of bodily fluids. Here we show that protein sensors in combination with a nanopore, acting as an electrical transducer, can accurately quantify metabolites in real time directly from nanoliter amounts of blood and other bodily fluids. Incorporation of the nanopore into portable electronic devices will allow developing sensitive, continuous, and non-invasive sensors for metabolites for point-of-care and home diagnostics. Protein nanopores are emerging as sensors for a variety of biomolecules. Here the authors develop a nanopore based on the bacterial toxin ClyA, in conjunction with binding proteins for glucose and asparagine, to detect these biomolecules simultaneously from a variety of unprocessed, diluted body fluids.
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Affiliation(s)
- Nicole Stéphanie Galenkamp
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 7, Groningen, 9747 AG, The Netherlands
| | - Misha Soskine
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 7, Groningen, 9747 AG, The Netherlands
| | - Jos Hermans
- Analytical Biochemistry, Department of Pharmacy, University of Groningen, Antonius Deusinglaan 1, Groningen, 9713 AV, The Netherlands
| | - Carsten Wloka
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 7, Groningen, 9747 AG, The Netherlands
| | - Giovanni Maglia
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 7, Groningen, 9747 AG, The Netherlands.
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Staphylococcus aureus produces pain through pore-forming toxins and neuronal TRPV1 that is silenced by QX-314. Nat Commun 2018; 9:37. [PMID: 29295977 PMCID: PMC5750211 DOI: 10.1038/s41467-017-02448-6] [Citation(s) in RCA: 98] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Accepted: 11/30/2017] [Indexed: 12/22/2022] Open
Abstract
The hallmark of many bacterial infections is pain. The underlying mechanisms of pain during live pathogen invasion are not well understood. Here, we elucidate key molecular mechanisms of pain produced during live methicillin-resistant Staphylococcus aureus (MRSA) infection. We show that spontaneous pain is dependent on the virulence determinant agr and bacterial pore-forming toxins (PFTs). The cation channel, TRPV1, mediated heat hyperalgesia as a distinct pain modality. Three classes of PFTs-alpha-hemolysin (Hla), phenol-soluble modulins (PSMs), and the leukocidin HlgAB-directly induced neuronal firing and produced spontaneous pain. From these mechanisms, we hypothesized that pores formed in neurons would allow entry of the membrane-impermeable sodium channel blocker QX-314 into nociceptors to silence pain during infection. QX-314 induced immediate and long-lasting blockade of pain caused by MRSA infection, significantly more than lidocaine or ibuprofen, two widely used clinical analgesic treatments.
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Huang G, Willems K, Soskine M, Wloka C, Maglia G. Electro-osmotic capture and ionic discrimination of peptide and protein biomarkers with FraC nanopores. Nat Commun 2017; 8:935. [PMID: 29038539 PMCID: PMC5715100 DOI: 10.1038/s41467-017-01006-4] [Citation(s) in RCA: 153] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Accepted: 08/09/2017] [Indexed: 12/13/2022] Open
Abstract
Biological nanopores are nanoscale sensors employed for high-throughput, low-cost, and long read-length DNA sequencing applications. The analysis and sequencing of proteins, however, is complicated by their folded structure and non-uniform charge. Here we show that an electro-osmotic flow through Fragaceatoxin C (FraC) nanopores can be engineered to allow the entry of polypeptides at a fixed potential regardless of the charge composition of the polypeptide. We further use the nanopore currents to discriminate peptide and protein biomarkers from 25 kDa down to 1.2 kDa including polypeptides differing by one amino acid. On the road to nanopore proteomics, our findings represent a rationale for amino-acid analysis of folded and unfolded polypeptides with nanopores. Biological nanopore–based protein sequencing and recognition is challenging due to the folded structure or non-uniform charge of peptides. Here the authors show that engineered FraC nanopores can overcome these problems and recognize biomarkers in the form of oligopeptides, polypeptides and folded proteins.
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Affiliation(s)
- Gang Huang
- Groningen Biomolecular Sciences & Biotechnology Institute, University of Groningen, 9747 AG, Groningen, The Netherlands
| | - Kherim Willems
- KU Leuven Department of Chemistry, Celestijnenlaan 200G, 3001, Leuven, Belgium.,Imec, Kapeldreef 75, 3001, Leuven, Belgium
| | - Misha Soskine
- Groningen Biomolecular Sciences & Biotechnology Institute, University of Groningen, 9747 AG, Groningen, The Netherlands
| | - Carsten Wloka
- Groningen Biomolecular Sciences & Biotechnology Institute, University of Groningen, 9747 AG, Groningen, The Netherlands.
| | - Giovanni Maglia
- Groningen Biomolecular Sciences & Biotechnology Institute, University of Groningen, 9747 AG, Groningen, The Netherlands.
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8
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Buyukdagli S, Blossey R. Beyond Poisson-Boltzmann: fluctuations and fluid structure in a self-consistent theory. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:343001. [PMID: 27357125 DOI: 10.1088/0953-8984/28/34/343001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Poisson-Boltzmann (PB) theory is the classic approach to soft matter electrostatics and has been applied to numerous physical chemistry and biophysics problems. Its essential limitations are in its neglect of correlation effects and fluid structure. Recently, several theoretical insights have allowed the formulation of approaches that go beyond PB theory in a systematic way. In this topical review, we provide an update on the developments achieved in the self-consistent formulations of correlation-corrected Poisson-Boltzmann theory. We introduce a corresponding system of coupled non-linear equations for both continuum electrostatics with a uniform dielectric constant, and a structured solvent-a dipolar Coulomb fluid-including non-local effects. While the approach is only approximate and also limited to corrections in the so-called weak fluctuation regime, it allows us to include physically relevant effects, as we show for a range of applications of these equations.
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Affiliation(s)
- S Buyukdagli
- Department of Physics, Bilkent University, Ankara 06800, Turkey
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9
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Bezrukov SM, Nestorovich EM. Inhibiting bacterial toxins by channel blockage. Pathog Dis 2016; 74:ftv113. [PMID: 26656888 PMCID: PMC4830228 DOI: 10.1093/femspd/ftv113] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 08/15/2015] [Accepted: 11/24/2015] [Indexed: 01/01/2023] Open
Abstract
Emergent rational drug design techniques explore individual properties of target biomolecules, small and macromolecule drug candidates, and the physical forces governing their interactions. In this minireview, we focus on the single-molecule biophysical studies of channel-forming bacterial toxins that suggest new approaches for their inhibition. We discuss several examples of blockage of bacterial pore-forming and AB-type toxins by the tailor-made compounds. In the concluding remarks, the most effective rationally designed pore-blocking antitoxins are compared with the small-molecule inhibitors of ion-selective channels of neurophysiology.
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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 20892, USA
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Miljković-Selimović B, Dinić M, Orlović J, Babić T. Staphylococcus aureus: Immunopathogenesis and Human Immunity. ACTA FACULTATIS MEDICAE NAISSENSIS 2015. [DOI: 10.1515/afmnai-2015-0025] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
SummaryConsidering a large number of pathogen factors that enable high virulence of a microorganism such as Staphylococcus aureus (S. aureus), it is essential to see them through the continuous adaptation to the newly acquired mechanisms of the host immune response and efforts to overcome these, allowing the bacteria a perfect ecological niche for growth, reproduction, and location of new hosts. Past efforts to create a vaccine that would provide effective protection against infections caused by S. aureus remained without success. The reasons for this stem from the outstanding adaptability skills of this microorganism to almost all environmental conditions, the existence of a numerous virulence factors whose mechanisms of action are not well known, as well as insufficient knowledge of the immune response to S. aureus infections. This review article deals with this issue from another perspective and emphasizes actual knowledge on virulence factors and immune response to S. aureus.
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The bicomponent pore-forming leucocidins of Staphylococcus aureus. Microbiol Mol Biol Rev 2015; 78:199-230. [PMID: 24847020 DOI: 10.1128/mmbr.00055-13] [Citation(s) in RCA: 189] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The ability to produce water-soluble proteins with the capacity to oligomerize and form pores within cellular lipid bilayers is a trait conserved among nearly all forms of life, including humans, single-celled eukaryotes, and numerous bacterial species. In bacteria, some of the most notable pore-forming molecules are protein toxins that interact with mammalian cell membranes to promote lysis, deliver effectors, and modulate cellular homeostasis. Of the bacterial species capable of producing pore-forming toxic molecules, the Gram-positive pathogen Staphylococcus aureus is one of the most notorious. S. aureus can produce seven different pore-forming protein toxins, all of which are believed to play a unique role in promoting the ability of the organism to cause disease in humans and other mammals. The most diverse of these pore-forming toxins, in terms of both functional activity and global representation within S. aureus clinical isolates, are the bicomponent leucocidins. From the first description of their activity on host immune cells over 100 years ago to the detailed investigations of their biochemical function today, the leucocidins remain at the forefront of S. aureus pathogenesis research initiatives. Study of their mode of action is of immediate interest in the realm of therapeutic agent design as well as for studies of bacterial pathogenesis. This review provides an updated perspective on our understanding of the S. aureus leucocidins and their function, specificity, and potential as therapeutic targets.
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Buyukdagli S, Blossey R, Ala-Nissila T. Ionic current inversion in pressure-driven polymer translocation through nanopores. PHYSICAL REVIEW LETTERS 2015; 114:088303. [PMID: 25768784 DOI: 10.1103/physrevlett.114.088303] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Indexed: 05/24/2023]
Abstract
We predict streaming current inversion with multivalent counterions in hydrodynamically driven polymer translocation events from a correlation-corrected charge transport theory including charge fluctuations around mean-field electrostatics. In the presence of multivalent counterions, electrostatic many-body effects result in the reversal of the DNA charge. The attraction of anions to the charge-inverted DNA molecule reverses the sign of the ionic current through the pore. Our theory allows for a comprehensive understanding of the complex features of the resulting streaming currents. The underlying mechanism is an efficient way to detect DNA charge reversal in pressure-driven translocation experiments with multivalent cations.
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Affiliation(s)
- Sahin Buyukdagli
- Department of Physics, Bilkent University, Ankara 06800, Turkey
- Institut de Recherche Interdisciplinaire USR3078 CNRS and Université Lille I, Parc de la Haute Borne, 52 Avenue de Halley, 59658 Villeneuve d'Ascq, France
| | - Ralf Blossey
- Institut de Recherche Interdisciplinaire USR3078 CNRS and Université Lille I, Parc de la Haute Borne, 52 Avenue de Halley, 59658 Villeneuve d'Ascq, France
| | - T Ala-Nissila
- Department of Applied Physics and COMP Center of Excellence, Aalto University School of Science, P.O. Box 11000, FI-00076 Aalto, Espoo, Finland
- Department of Physics, Brown University, Providence, Box 1843, Rhode Island 02912-1843, USA
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Buyukdagli S, Ala-Nissila T. Controlling polymer translocation and ion transport via charge correlations. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:12907-15. [PMID: 25310861 DOI: 10.1021/la503327j] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We develop a correlation-corrected transport theory in order to predict ionic and polymer transport properties of membrane nanopores under physical conditions where mean-field electrostatics breaks down. The experimentally observed low KCl conductivity of open α-hemolysin pores is quantitatively explained by the presence of surface polarization effects. Upon the penetration of a DNA molecule into the pore, these polarization forces combined with the electroneutrality of DNA sets a lower boundary for the ionic current, explaining the weak salt dependence of blocked pore conductivities at dilute ion concentrations. The addition of multivalent counterions to the solution results in the reversal of the polymer charge and the direction of the electroosmotic flow. With trivalent spermidine or quadrivalent spermine molecules, the charge inversion is strong enough to stop the translocation of the polymer and to reverse its motion. This mechanism can be used efficiently in translocation experiments in order to improve the accuracy of DNA sequencing by minimizing the translocation velocity of the polymer.
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Affiliation(s)
- Sahin Buyukdagli
- Institut de Recherche Interdisciplinaire USR3078 CNRS and Université Lille I , Parc de la Haute Borne, 52 Avenue de Halley, 59658 Villeneuve d'Ascq, France
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Padmaja RJ, Halami PM. Immunogenicity of Staphylococcus aureus LukM/F'-PV recombinant subunits: validation of diagnostic potential and evaluation of protective efficacy in vitro. Vet Microbiol 2014; 170:358-67. [PMID: 24674742 DOI: 10.1016/j.vetmic.2014.02.041] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2013] [Revised: 02/19/2014] [Accepted: 02/24/2014] [Indexed: 11/30/2022]
Abstract
Leukotoxin M/F'-Panton Valentine (LukM/F'-PV), a beta pore-forming toxin secreted by Staphylococcus aureus, is a major virulence factor involved in the pathogenesis of bovine mastitis. The present study was aimed to determine immunogenicity of two recombinant subunits of LukM/F'-PV, rLukM (MW 38 kDa) and rLukF (MW 39 kDa), develop and validate an indirect enzyme linked immunosorbent assay (ELISA) using polyclonal antibodies raised in rabbits, and evaluate applicability of the assay to diagnose clinical and subclinical bovine mastitis. Additionally, in vitro assays were conducted to determine abilities of antibodies to neutralize cytotoxicity of the native leukotoxin. A total of 87 bovine milk samples (healthy, subclinical and clinical mastitis) were evaluated for the presence of toxin determinants. Receiver-operator characteristic curve for the experimental ELISA values statistically interpreted a cut-off score of >0.109 OD405, with an assay specificity of 100% and sensitivity in the range of 80-87.5%. In addition, area under curve of 0.93-0.98 revealed the test was accurate in categorizing samples from infected and non-infected bovine. The rLukF IgG-ELISA was more sensitive than rLukM IgG-ELISA. Furthermore, it was evident from MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium) dye reduction, indirect immunofluorescence and lactate dehydrogenase assays that anti-rLukM/rLukF antibodies, with high neutralizing titers, inhibited in vitro leukotoxic activity and protected bovine neutrophil membrane integrity from cytotoxicity of native leukotoxin. The findings demonstrated that antibodies produced from recombinant subunits contribute to specific and sensitive immunodiagnosis and may also have the potential to provide passive therapeutic benefit in the management of bovine mastitis.
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Affiliation(s)
- R J Padmaja
- Department of Food Microbiology, CSIR-Central Food Technological Research Institute, Mysore 570 020, India
| | - P M Halami
- Department of Food Microbiology, CSIR-Central Food Technological Research Institute, Mysore 570 020, India.
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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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Martel A, Cross B. Handling of artificial membranes using electrowetting-actuated droplets on a microfluidic device combined with integrated pA-measurements. BIOMICROFLUIDICS 2012; 6:12813-128137. [PMID: 22662080 PMCID: PMC3365332 DOI: 10.1063/1.3665719] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2011] [Accepted: 11/14/2011] [Indexed: 06/01/2023]
Abstract
Artificial membranes, as a controllable environment, are an essential tool to study membrane proteins. Electrophysiology provides information about the ion transport mechanism across a membrane at the single-protein level. Unfortunately, high-throughput studies and screening are not accessible to electrophysiology because it is a set of not automated and technically delicate methods. Therefore, it is necessary to automate and parallelize electrophysiology measurement in artificial membranes. Here, we present a first step toward this goal: the fabrication and characterization of a microfluidic device integrating electrophysiology measurements and the handling of an artificial membrane which includes its formation, its displacement and the separation of its leaflets using electrowetting actuation of sub-μL droplets. To validate this device, we recorded the insertion of a model porin, α-hemolysin.
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Hammerstein AF, Jayasinghe L, Bayley H. Subunit dimers of alpha-hemolysin expand the engineering toolbox for protein nanopores. J Biol Chem 2011; 286:14324-34. [PMID: 21324910 PMCID: PMC3077633 DOI: 10.1074/jbc.m111.218164] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2011] [Revised: 02/10/2011] [Indexed: 12/27/2022] Open
Abstract
Staphylococcal α-hemolysin (αHL) forms a heptameric pore that features a 14-stranded transmembrane β-barrel. We attempted to force the αHL pore to adopt novel stoichiometries by oligomerizing subunit dimers generated by in vitro transcription and translation of a tandem gene. However, in vitro transcription and translation also produced truncated proteins, monomers, that were preferentially incorporated into oligomers. These oligomers were shown to be functional heptamers by single-channel recording and had a similar mobility to wild-type heptamers in SDS-polyacrylamide gels. Purified full-length subunit dimers were then prepared by using His-tagged protein. Again, single-channel recording showed that oligomers made from these dimers are functional heptamers, implying that one or more subunits are excluded from the central pore. Therefore, the αHL pore resists all structures except those that possess seven subunits immediately surrounding the central axis. Although we were not able to change the stoichiometry of the central pore of αHL by the concatenation of subunits, we extended our findings to prepare pores containing one subunit dimer and five monomers and purified them by SDS-PAGE. Two half-chelating ligands were then installed at adjacent sites, one on each subunit of the dimer. Single-channel recording showed that pores formed from this construct formed complexes with divalent metal ions in a similar fashion to pores containing two half-chelating ligands on the same subunit, confirming that the oligomers had assembled with seven subunits around the central lumen. The ability to incorporate subunit dimers into αHL pores increases the range of structures that can be obtained from engineered protein nanopores.
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Affiliation(s)
- Anne F. Hammerstein
- From the Department of Chemistry, University of Oxford, Oxford OX1 3TA, United Kingdom
| | - Lakmal Jayasinghe
- From the Department of Chemistry, University of Oxford, Oxford OX1 3TA, United Kingdom
| | - Hagan Bayley
- From the Department of Chemistry, University of Oxford, Oxford OX1 3TA, United Kingdom
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Tan Q, Shim JW, Gu LQ. Separation of heteromeric potassium channel Kcv towards probing subunit composition-regulated ion permeation and gating. FEBS Lett 2010; 584:1602-8. [PMID: 20303961 DOI: 10.1016/j.febslet.2010.03.023] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2010] [Revised: 03/12/2010] [Accepted: 03/15/2010] [Indexed: 11/19/2022]
Abstract
The chlorella virus-encoded Kcv can form a homo-tetrameric potassium channel in lipid membranes. This miniature peptide can be synthesized in vitro, and the tetramer purified from the SDS-polyacrylamide gel retains the K(+) channel functionality. Combining this capability with the mass-tagging method, we propose a simple, straightforward approach that can generically manipulate individual subunits in the tetramer, thereby enabling the detection of contribution from individual subunits to the channel functions. Using this approach, we showed that the structural change in the selectivity filter from only one subunit is sufficient to cause permanent channel inactivation ("all-or-none" mechanism), whereas the mutation near the extracellular entrance additively modifies the ion permeation with the number of mutant subunits in the tetramer ("additive" mechanism).
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Affiliation(s)
- Qiulin Tan
- Department of Biological Engineering, Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO 65211, USA
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19
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Graber HU, Naskova J, Studer E, Kaufmann T, Kirchhofer M, Brechbühl M, Schaeren W, Steiner A, Fournier C. Mastitis-related subtypes of bovine Staphylococcus aureus are characterized by different clinical properties. J Dairy Sci 2009; 92:1442-51. [PMID: 19307625 DOI: 10.3168/jds.2008-1430] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Based on a former study from our group, one subtype of Staphylococcus aureus was associated with high within-herd prevalence of mastitis, whereas the other subtypes were associated with a low prevalence (sporadic intramammary infection). To confirm this hypothesis, a prospective study was done in 29 Swiss dairy herds. In particular, milk samples were collected from 10 herds with Staph. aureus herd problems (cases) and compared with samples from 19 herds with only sporadic cases of with Staph. aureus intramammary infection (controls). The isolates were tested for their virulence gene pattern and genotyped by PCR amplification of the 16S-23S rRNA intergenic spacer. The patterns and genotypes were then associated and compared with epidemiological and clinical data. Confirming the hypothesis, one particular subtype (genotype B) was associated with high within-herd and within-cow prevalence of intramammary infection, whereas the other subtypes were associated with low within-herd prevalence and infected single quarters. The gene patterns and genotypes were highly related, demonstrating the genetic diversity of the genotypes. The somatic cell counts were clearly increased in herds with a genotype B problem compared with herds with infections of other genotypes. Based on the different clinical properties and treatment consequences associated with these different genotypes found in Switzerland, we recommend subtyping Staph. aureus in other countries to determine if this finding is universally applicable.
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Affiliation(s)
- H U Graber
- Clinic for Ruminants, Department of Clinical Veterinary Medicine, University of Berne, Bremgartenstrasse 109a, PO Box 8466, 3001 Berne, Switzerland.
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20
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Syeda R, Holden MA, Hwang WL, Bayley H. Screening Blockers Against a Potassium Channel with a Droplet Interface Bilayer Array. J Am Chem Soc 2008; 130:15543-8. [DOI: 10.1021/ja804968g] [Citation(s) in RCA: 121] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ruhma Syeda
- Department of Chemistry, University of Oxford, Mansfield Road, Oxford, OX1 3TA, U.K
| | - Matthew A. Holden
- Department of Chemistry, University of Oxford, Mansfield Road, Oxford, OX1 3TA, U.K
| | - William L. Hwang
- Department of Chemistry, University of Oxford, Mansfield Road, Oxford, OX1 3TA, U.K
| | - Hagan Bayley
- Department of Chemistry, University of Oxford, Mansfield Road, Oxford, OX1 3TA, U.K
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21
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Fournier C, Kuhnert P, Frey J, Miserez R, Kirchhofer M, Kaufmann T, Steiner A, Graber HU. Bovine Staphylococcus aureus: association of virulence genes, genotypes and clinical outcome. Res Vet Sci 2008; 85:439-48. [PMID: 18358507 DOI: 10.1016/j.rvsc.2008.01.010] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2007] [Revised: 01/15/2008] [Accepted: 01/27/2008] [Indexed: 10/22/2022]
Abstract
Based on our clinical experience on bovine mastitis, we hypothesized that subtypes of Staphylococcus aureus (S. aureus) exist which differ in their contagious and pathogenic properties. In order to investigate this hypothesis, we analyzed strains of S. aureus isolated from spontaneous intramammary infection (IMI) with their virulence gene patterns and genotypes obtained by PCR amplification of the 16S-23S rRNA intergenic spacer (RS-PCR). The genotypes were then associated with epidemiological and clinical data including 26 herds. The results demonstrated a high association between genotypes and virulence gene patterns as well as between epidemiological and pathogenic properties of S. aureus. In particular, genotype B was related to high contagiosity and increased pathogenicity whereas the other types (C, OG) were found with infection of single cows. Because of the high clinical relevance, our results indicate the need to subtype the IMI-associated strains of S. aureus in the future.
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Affiliation(s)
- C Fournier
- Department of Clinical Veterinary Medicine, Vetsuisse-Faculty, University of Berne, 3001 Berne, Switzerland
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22
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Das SK, Darshi M, Cheley S, Wallace MI, Bayley H. Membrane protein stoichiometry determined from the step-wise photobleaching of dye-labelled subunits. Chembiochem 2007; 8:994-9. [PMID: 17503420 DOI: 10.1002/cbic.200600474] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Somes K Das
- Department of Molecular & Cellular Medicine, The Texas A&M University System Health Science Center, College Station, TX 77843-1114, USA
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23
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White RJ, Ervin EN, Yang T, Chen X, Daniel S, Cremer PS, White HS. Single ion-channel recordings using glass nanopore membranes. J Am Chem Soc 2007; 129:11766-75. [PMID: 17784758 DOI: 10.1021/ja073174q] [Citation(s) in RCA: 215] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Protein ion-channel recordings using a glass nanopore (GNP) membrane as the support structure for lipid bilayer membranes are presented. The GNP membrane is composed of a single conical-shaped nanopore embedded in a approximately 50 microm-thick glass membrane chemically modified with a 3-cyanopropyldimethylchlorosilane monolayer to produce a surface of intermediate hydrophobicity. This surface modification results in lipid monolayer formation on the glass surface and a lipid bilayer suspended across the small orifice (100-400 nm-radius) of the GNP membrane, while allowing aqueous solutions to fully wet the glass nanopore. The GNP membrane/bilayer structures, which exhibit ohmic seal resistances of approximately 70 GOmega and electrical breakdown voltages of approximately 0.8 V, are exceptionally stable to mechanical disturbances and have lifetimes of at least 2 weeks. These favorable characteristics result from the very small area of bilayer (10(-10)-10(-8) cm(2)) that is suspended across the GNP membrane orifice. Fluorescence microscopy and vibrational sum frequency spectroscopy demonstrate that a lipid monolayer forms on the 3-cyanopropyl-dimethylchlorosilane modified glass surface with the lipid tails oriented toward the glass. The GNP membrane/bilayer structure is well suited for single ion-channel recordings. Reproducible insertion of the protein ion channel, wild-type alpha-hemolysin (WTalphaHL), and stochastic detection of a small molecule, heptakis(6-O-sulfo)-beta-cyclodextrin, are demonstrated. In addition, the insertion and removal of WTalphaHL channels are reproducibly controlled by applying small pressures (-100 to 350 mmHg) across the lipid bilayer. The electrical and mechanical stability of the bilayer, the ease of which bilayer formation is achieved, and the ability to control ion-channel insertion, coupled with the small bilayer capacitance of the GNP membrane-based system, provide a new and nearly optimal system for single ion-channel recordings.
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Affiliation(s)
- Ryan J White
- Department of Chemistry, University of Utah, 315 S 1400 E, Salt Lake City, Utah 84112, USA
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24
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Hwang WL, Holden MA, White S, Bayley H. Electrical Behavior of Droplet Interface Bilayer Networks: Experimental Analysis and Modeling. J Am Chem Soc 2007; 129:11854-64. [PMID: 17764183 DOI: 10.1021/ja074071a] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Aqueous droplets submerged in an oil-lipid mixture become enclosed by a lipid monolayer. The droplets can be connected to form robust networks of droplet interface bilayers (DIBs) with functions such as a biobattery and a light sensor. Such DIB networks might be used as model systems for the study of membrane-based biological phenomena. In this study, we develop and experimentally validate an electrical modeling approach for DIB networks by applying it to describe the current flow through a simple network containing protein pores and blocking molecules. We demonstrate the use of SPICE (Simulation Program with Integrated Circuit Emphasis) for simulating the electrical behavior of DIB networks. The modular and scalable nature of DIB networks should enable a straightforward extension of the analysis presented in this paper to large, complex networks.
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Affiliation(s)
- William L Hwang
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, OX1 3TA, England, UK.
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25
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Abstract
We form networks from aqueous droplets by submerging them in an oil/lipid mixture. When the droplets are joined together, the lipid monolayers surrounding them combine at the interface to form a robust lipid bilayer. Various protein channels and pores can incorporate into the droplet-interface bilayer (DIB), and the application of a potential with electrodes embedded within the droplets allows ionic currents to be driven across the interface and measured. By joining droplets in linear or branched geometries, functional bionetworks can be created. Although the interfaces between neighboring droplets comprise only single lipid bilayers, the structures of the networks are long-lived and robust. Indeed, a single droplet can be "surgically" excised from a network and replaced with a new droplet without rupturing adjacent DIBs. Networks of droplets can be powered with internal "biobatteries" that use ion gradients or the light-driven proton pump bacteriorhodopsin. Besides their interest as coupled protocells, the droplets can be used as devices for ultrastable bilayer recording with greatly reduced electrolyte volume, which will permit their use in rapid screening applications.
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Affiliation(s)
- Matthew A Holden
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Mansfield Road, OX1 3TA Oxford, UK.
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26
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Shim JW, Yang M, Gu LQ. In vitro synthesis, tetramerization and single channel characterization of virus-encoded potassium channel Kcv. FEBS Lett 2007; 581:1027-34. [PMID: 17316630 DOI: 10.1016/j.febslet.2007.02.005] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2007] [Revised: 02/02/2007] [Accepted: 02/02/2007] [Indexed: 10/23/2022]
Abstract
Chlorella virus-encoded membrane protein Kcv represents a new class of potassium channel. This 94-amino acids miniature K(+) channel consists of two trans-membrane alpha-helix domains intermediated by a pore domain that contains a highly conserved K(+) selectivity filter. Therefore, as an archetypal K(+) channel, the study of Kcv may yield valuable insights into the structure-function relationships underlying this important class of ion channel. Here, we report a series of new properties of Kcv. We first verified Kcv can be synthesized in vitro. By co-synthesis and assembly of wild-type and the tagged version of Kcv, we were able to demonstrate a tetrameric stoichiometry, a molecular structure adopted by all known K(+) channels. Most notably, the tetrameric Kcv complex retains its functional integrity in SDS (strong detergent)-containing solutions, a useful feature that allows for direct purification of protein from polyacrylamide gel. Once purified, the tetramer can form single potassium-selective ion channels in a lipid bilayer with functions consistent to the heterologously expressed Kcv. These finding suggest that the synthetic Kcv can serve as a model of virus-encoded K(+) channels; and its newly identified properties can be applied to the future study on structure-determined mechanisms such as K(+) channel functional stoichiometry.
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Affiliation(s)
- Ji Wook Shim
- Department of Biological Engineering, Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO 65211, USA
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27
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Robertson KP, Smith CJ, Gough AM, Rocha ER. Characterization of Bacteroides fragilis hemolysins and regulation and synergistic interactions of HlyA and HlyB. Infect Immun 2006; 74:2304-16. [PMID: 16552061 PMCID: PMC1418898 DOI: 10.1128/iai.74.4.2304-2316.2006] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
This study describes the presence of 10 hemolysin orthologs in the genome of the opportunistic human anaerobic pathogen Bacteroides fragilis, which is currently classified as a nonhemolytic bacterium. The hemolysins were designated HlyA through HlyI plus HlyIII. All cloned hemolysin genes were able to confer hemolytic activity to a nonhemolytic Escherichia coli strain on blood agar plates. Interestingly, HlyH was found to be present in the genome of the B. fragilis NCTC9343 strain but absent in strains 638R, YCH46, and Bacteroides thetaiotaomicron VPI-5482. The hemolysins HlyA, HlyB, and HlyIII were selected for further characterization. HlyA, HlyB, and HlyIII were cytolytic to erythrocytes on liquid hemolytic assay. When hlyA and hlyB were expressed together in a nonhemolytic E. coli strain, the strain showed enhanced hemolytic activity on blood agar plates. Further analysis revealed that HlyA and HlyB have synergistic hemolytic activity as detected by the liquid hemolytic assay. In addition, the two-component hemolysins HlyA and HlyB form a protein-protein complex in vivo as determined by bacterial two-hybrid system assay. The hlyB and hlyA genes are organized in an operon that is coordinately regulated by iron and oxygen. Northern blot hybridization analysis revealed that hlyBA were expressed as a bicistronic mRNA induced approximately 2.5-fold under low-iron conditions and repressed in iron-rich medium. The normal iron-regulated expression of hlyBA mRNA was lost in the furA mutant strain. In contrast, the hlyA gene was also expressed as a single mRNA in iron-rich medium, but its expression was reduced approximately threefold under low-iron conditions in a Fur-independent manner. This suggests that hlyA alone is regulated by an unidentified iron-dependent regulator. Moreover, the expression levels of hlyBA and hlyA were reduced about threefold following oxygen exposure and treatment with hydrogen peroxide. Taken together, these results suggest that iron and oxidative stress have an effect on the control of hlyBA and hlyA transcriptional levels. A hlyBA mutant was constructed, and its hemolytic activity was greatly diminished compared to those of the hlyIII mutant and parent strains. In addition, the hlyBA mutant had a significant modification in colony morphology and growth deficiency compared to the parent strain. The implications of these findings for the pathophysiology of B. fragilis in extraintestinal infections and competition in ecological systems for this organism are discussed.
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Affiliation(s)
- Kirstin P Robertson
- Department of Microbiology and Immunology, East Carolina University Brody School of Medicine, Biotechnology Bldg., Room 130, 600 Moye Blvd., Greenville, NC 27834, USA
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28
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Holden MA, Jayasinghe L, Daltrop O, Mason A, Bayley H. Direct transfer of membrane proteins from bacteria to planar bilayers for rapid screening by single-channel recording. Nat Chem Biol 2006; 2:314-8. [PMID: 16680158 DOI: 10.1038/nchembio793] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2006] [Accepted: 04/17/2006] [Indexed: 11/09/2022]
Abstract
Although the examination of membrane proteins in planar bilayers is a powerful methodology for evaluating their pharmacology and physiological roles, introducing membrane proteins into bilayers is often a difficult process. Here, we use a mechanical probe to transfer membrane proteins directly from Escherichia coli expression colonies to artificial lipid bilayers. In this way, single-channel electrical recordings can be made from both of the major classes of membrane proteins, alpha-helix bundles and beta barrels, which are represented respectively by a K(+) channel and a bacterial pore-forming toxin. Further, we examined the bicomponent toxin leukocidin (Luk), which is composed of LukF and LukS subunits. We mixed separate LukF- and LukS-expressing colonies and transferred the mixture to a planar bilayer, which generated functional Luk pores. By this means, we rapidly screened binary combinations of mutant Luk subunits for a specific function: the ability to bind a molecular adaptor. We suggest that direct transfer from cells to bilayers will be useful in several aspects of membrane proteomics and in the construction of sensor arrays.
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Affiliation(s)
- Matthew A Holden
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Mansfield Road, Oxford OX1 3TA, UK.
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29
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Viero G, Cunaccia R, Prévost G, Werner S, Monteil H, Keller D, Joubert O, Menestrina G, Dalla Serra M. Homologous versus heterologous interactions in the bicomponent staphylococcal gamma-haemolysin pore. Biochem J 2006; 394:217-25. [PMID: 16241903 PMCID: PMC1386019 DOI: 10.1042/bj20051210] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Staphylococcal gamma-haemolysin HlgA-HlgB forms a beta-barrel transmembrane pore in cells and in model membranes. The pore is formed by the oligomerization of two different proteins and a still debated number of monomers. To clarify the topology of the pore, we have mutated single residues - placed near the right and left interfaces of each monomer into cysteine. The mutants were labelled with fluorescent probes, forming a donor-acceptor pair for FRET (fluorescence resonance energy transfer). Heterologous couples (labelled on complementary left and right interfaces) displayed a marked FRET, suggesting extensive HlgA-HlgB or HlgB-HlgA contacts. Heterologous control couples (with both components labelled on the same side) showed absent or low FRET. We found the same result for the homologous couple formed by HlgA [i.e. HlgA-HlgA in the presence of wt (wild-type) HlgB]. The homologous HlgB couple (HlgB-HlgB labelled on left and right interfaces and in the presence of wt HlgA) displayed a transient, declining FRET, which may indicate fast formation of an intermediate that is consumed during pore formation. We conclude that bicomponent pores are assembled by alternating heterologous monomers.
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Affiliation(s)
- Gabriella Viero
- *Istituto Trentino di Cultura (ITC) and Consiglio Nazionale delle Ricerche (CNR), Istituto di Biofisica, Sezione di Trento, Via Sommarive 18, I-38050 Povo (TN), Italy
| | - Romina Cunaccia
- *Istituto Trentino di Cultura (ITC) and Consiglio Nazionale delle Ricerche (CNR), Istituto di Biofisica, Sezione di Trento, Via Sommarive 18, I-38050 Povo (TN), Italy
| | - Gilles Prévost
- †Institut de Bactériologie de la Faculté de Médecine, UPRES EA-3432, ULP-HUS, 3 rue Koeberlé, F-67000 Strasbourg, France
| | - Sandra Werner
- †Institut de Bactériologie de la Faculté de Médecine, UPRES EA-3432, ULP-HUS, 3 rue Koeberlé, F-67000 Strasbourg, France
| | - Henri Monteil
- †Institut de Bactériologie de la Faculté de Médecine, UPRES EA-3432, ULP-HUS, 3 rue Koeberlé, F-67000 Strasbourg, France
| | - Daniel Keller
- †Institut de Bactériologie de la Faculté de Médecine, UPRES EA-3432, ULP-HUS, 3 rue Koeberlé, F-67000 Strasbourg, France
| | - Olivier Joubert
- †Institut de Bactériologie de la Faculté de Médecine, UPRES EA-3432, ULP-HUS, 3 rue Koeberlé, F-67000 Strasbourg, France
| | - Gianfranco Menestrina
- *Istituto Trentino di Cultura (ITC) and Consiglio Nazionale delle Ricerche (CNR), Istituto di Biofisica, Sezione di Trento, Via Sommarive 18, I-38050 Povo (TN), Italy
| | - Mauro Dalla Serra
- *Istituto Trentino di Cultura (ITC) and Consiglio Nazionale delle Ricerche (CNR), Istituto di Biofisica, Sezione di Trento, Via Sommarive 18, I-38050 Povo (TN), Italy
- To whom correspondence should be addressed (email )
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30
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Jayasinghe L, Bayley H. The leukocidin pore: evidence for an octamer with four LukF subunits and four LukS subunits alternating around a central axis. Protein Sci 2005; 14:2550-61. [PMID: 16195546 PMCID: PMC2253299 DOI: 10.1110/ps.051648505] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The staphylococcal alpha-hemolysin (alphaHL) and leukocidin (Luk) polypeptides are members of a family of related beta-barrel pore-forming toxins. Upon binding to susceptible cells, alphaHL forms water-filled homoheptameric transmembrane pores. By contrast, Luk pores are formed by two classes of subunit, F and S, rendering a heptameric structure displeasing on symmetry grounds at least. Both the subunit stoichiometry and arrangement within the Luk pore have been contentious issues. Here we use chemical and genetic approaches to show that (1) the predominant, or perhaps the only, form of the Luk pore is an octamer; (2) the subunit stoichiometry is 1:1; and (3) the subunits are arranged in an alternating fashion about a central axis of symmetry, at least when a fused LukS-LukF construct is used. The experimental approaches we have used also open up new avenues for engineering the arrangement of the subunits of beta-barrel pore-forming toxins.
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Affiliation(s)
- Lakmal Jayasinghe
- Department of Chemistry, University of Oxford, Oxford OX1 3TA, England, United Kingdom
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31
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Miles G, Jayasinghe L, Bayley H. Assembly of the Bi-component leukocidin pore examined by truncation mutagenesis. J Biol Chem 2005; 281:2205-14. [PMID: 16269405 DOI: 10.1074/jbc.m510842200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Staphylococcal leukocidin (Luk) and alpha-hemolysin (alphaHL) are members of the same family of beta barrel pore-forming toxins (betaPFTs). Although the alphaHL pore is a homoheptamer, the Luk pore is formed by the co-assembly of four copies each of the two distantly related polypeptides, LukF and LukS, to form an octamer. Here, we examine N- and C-terminal truncation mutants of LukF and LukS. LukF subunits missing up to nineteen N-terminal amino acids are capable of producing stable, functional hetero-oligomers with WT LukS. LukS subunits missing up to fourteen N-terminal amino acids perform similarly in combination with WT LukF. Further, the simultaneous truncation of both LukF and LukS is tolerated. Both Luk subunits are vulnerable to short deletions at the C terminus. Interestingly, the N terminus of the LukS polypeptide becomes resistant to proteolytic digestion in the fully assembled Luk pore while the N terminus of LukF remains in an exposed conformation. The results from this work and related experiments on alphaHL suggest that, although the N termini of betaPFTs may undergo reorganization during assembly, they are dispensable for the formation of functional pores.
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Affiliation(s)
- George Miles
- Department of Medical Biochemistry & Genetics, Texas A&M University System Health Science Center, College Station, TX 77843-1114, USA
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32
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Jayasinghe L, Miles G, Bayley H. Role of the amino latch of staphylococcal alpha-hemolysin in pore formation: a co-operative interaction between the N terminus and position 217. J Biol Chem 2005; 281:2195-204. [PMID: 16227199 DOI: 10.1074/jbc.m510841200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Staphylococcal alpha-hemolysin (alphaHL) is a beta barrel pore-forming toxin that is secreted by the bacterium as a water-soluble monomeric protein. Upon binding to susceptible cells, alphaHL assembles via an inactive prepore to form a water-filled homoheptameric transmembrane pore. The N terminus of alphaHL, which in the crystal structure of the fully assembled pore forms a latch between adjacent subunits, has been thought to play a vital role in the prepore to pore conversion. For example, the deletion of two N-terminal residues produced a completely inactive protein that was arrested in assembly at the prepore stage. In the present study, we have re-examined assembly with a comprehensive set of truncation mutants. Surprisingly, we found that after truncation of up to 17 amino acids, the ability of alphaHL to form functional pores was diminished, but still substantial. We then discovered that the mutation Ser(217) --> Asn, which was present in our original set of truncations but not in the new ones, promotes complete inactivation upon truncation of the N terminus. Therefore, the N terminus of alphaHL cannot be critical for the prepore to pore transformation as previously thought. Residue 217 is involved in the assembly process and must interact indirectly with the distant N terminus during the last step in pore formation. In addition, we provide evidence that an intact N terminus prevents the premature oligomerization of alphaHL monomers in solution.
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Affiliation(s)
- Lakmal Jayasinghe
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Mansfield Road, Oxford OX1 3TA, United Kingdom
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33
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Holden MA, Bayley H. Direct introduction of single protein channels and pores into lipid bilayers. J Am Chem Soc 2005; 127:6502-3. [PMID: 15869249 DOI: 10.1021/ja042470p] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We have developed a mechanical method for inserting single pores and channels into lipid bilayers. A hand-operated hydrogel probe, coated with a layer of proteins, is mechanically engaged with the lipid bilayer. The two major classes of membrane proteins (beta barrels and alpha-helix bundles) that can be inserted, thereby demonstrating the wide applicability of the approach. Recordings from the proteins show that they retain electrical properties that are the same as those of proteins inserted from solution. Protein-loaded probes can be used repeatedly, allowing individual pores to be rapidly screened one at a time. The method has implications for fundamental studies of cell membranes, array fabrication, and chemical screening.
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Affiliation(s)
- Matthew A Holden
- Department of Chemistry, University of Oxford, Oxford OX1 3TA, United Kingdom.
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34
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Kang XF, Gu LQ, Cheley S, Bayley H. Single Protein Pores Containing Molecular Adapters at High Temperatures. Angew Chem Int Ed Engl 2005. [DOI: 10.1002/ange.200461885] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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35
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Kang XF, Gu LQ, Cheley S, Bayley H. Single Protein Pores Containing Molecular Adapters at High Temperatures. Angew Chem Int Ed Engl 2005; 44:1495-9. [PMID: 15678432 DOI: 10.1002/anie.200461885] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Xiao-Feng Kang
- Department of Medical Biochemistry and Genetics, Texas A&M University System Health Science Center, College Station, TX 77843-1114, USA
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36
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Valeva A, Walev I, Weis S, Boukhallouk F, Wassenaar TM, Endres K, Fahrenholz F, Bhakdi S, Zitzer A. A cellular metalloproteinase activates Vibrio cholerae pro-cytolysin. J Biol Chem 2004; 279:25143-8. [PMID: 15066987 DOI: 10.1074/jbc.m313913200] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Many strains of Vibrio cholerae produce a cytolysin (VCC) that forms oligomeric transmembrane pores in animal cells. The molecule is secreted as a procytolysin (pro-VCC) of 79 kDa that must be cleaved at the N terminus to generate the active 65-kDa toxin. Processing can occur in solution, and previous studies have described the action of mature VCC thus generated. However, little is known about the properties of pro-VCC itself. In this study, it is shown that pro-VCC exist as a monomer in solution and binds as a monomer to eukaryotic cells. Bound pro-VCC can then be activated either by exogenous, extracellular, or by endogenous, cell-bound proteases. In both cases, cleavage generates the 65-kDa VCC that oligomerizes to form transmembrane pores. A wide variety of exogenous proteinases can mediate activation. In contrast, the activating cellular protease is selectively inhibited by the hydroxamate inhibitor TAPI, and thus probable candidates are members of the ADAM-metalloproteinase family. Furin, MMP-2, MMP-9, and serine proteinases were excluded. Cells over-expressing ADAM-17, also known as tumor necrosis factor alpha converting enzyme, displayed increased activation of VCC, and knockout cells lacking ADAM-17 had a markedly decreased capacity to cleave the protoxin. The possibility is raised that pro-VCC is targeted to membrane sites that selectively contain or are accessible to cellular ADAM-metalloproteinases. Although many microbial toxins are activated by furin, this is the first evidence for processing by a cellular metalloproteinase. We identified ADAM-17 as a potent activator of pro-VCC.
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Affiliation(s)
- Angela Valeva
- Institute of Medical Microbiology and Hygiene, University of Mainz, D55101 Mainz, Germany.
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37
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Menestrina G, Dalla Serra M, Comai M, Coraiola M, Viero G, Werner S, Colin DA, Monteil H, Prévost G. Ion channels and bacterial infection: the case of beta-barrel pore-forming protein toxins of Staphylococcus aureus. FEBS Lett 2003; 552:54-60. [PMID: 12972152 DOI: 10.1016/s0014-5793(03)00850-0] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Staphylococcus aureus strains causing human pathologies produce several toxins, including a pore-forming protein family formed by the single-component alpha-hemolysin and the bicomponent leukocidins and gamma-hemolysins. The last comprise two protein elements, S and F, that co-operatively form the active toxin. alpha-Hemolysin is always expressed by S. aureus strains, whereas bicomponent leukotoxins are more specifically involved in a few diseases. X-ray crystallography of the alpha-hemolysin pore has shown it is a mushroom-shaped, hollow heptamer, almost entirely consisting of beta-structure. Monomeric F subunits have a very similar core structure, except for the transmembrane stem domain which has to refold during pore formation. Large deletions in this domain abolished activity, whereas shorter deletions sometimes improved it, possibly by removing some of the interactions stabilizing the folded structure. Even before stem extension is completed, the formation of an oligomeric pre-pore can trigger Ca(2+)-mediated activation of some white cells, initiating an inflammatory response. Within the bicomponent toxins, gamma-hemolysins define three proteins (HlgA, HlgB, HlgC) that can generate two toxins: HlgA+HlgB and HlgC+HlgB. Like alpha-hemolysin they form pores in planar bilayers with similar conductance, but opposite selectivity (cation instead of anion) for the presence of negative charges in the ion pathway. gamma-Hemolysin pores seem to be organized as alpha-hemolysin, but should contain an even number of each component, alternating in a 1:1 stoichiometry.
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Affiliation(s)
- G Menestrina
- CNR-ITC Istituto di Biofisica, Sezione di Trento, Via Sommarive 18, I-38050 Povo, Italy.
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38
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Martin PE, Errington RJ, Evans WH. Gap junction assembly: multiple connexin fluorophores identify complex trafficking pathways. CELL COMMUNICATION & ADHESION 2003; 8:243-8. [PMID: 12064596 DOI: 10.3109/15419060109080731] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The assembly of gap junction channels was studied using mammalian cells expressing connexin (Cx) 26, 32 and 43 in which the carboxyl terminus was fused to green, yellow or cyan fluorescent proteins (GFP, YFP, CFP). Intracellular targeting of Cx32-CFP and 43-GFP to gap junctions was disrupted by brefeldin A treatment and resulted in a severe loss of gap junctional intercellular communication reflected by low intercellular dye transfer. Cells expressing Cx43-GFP exposed to nocodazole showed normal targeting to gap junctions and dye transfer. Cx32 and 43 thus appear to be transported and assembled into gap junctions via the classical secretory pathway. In contrast, we found that assembly of Cx26-GFP into functional gap junctions was relatively unaffected by treatment of cells with brefeldin A, but was extremely sensitive to nocodazole treatment. Coexpression of Cx26-YFP and Cx32-CFP indicated a different intracellular distribution that was accentuated in the presence of brefeldin A, with the gap junctions in these cells constructed predominantly of Cx26-YFP. A site specific mutation in the first transmembrane domain that distinguished Cx32 from Cx26 (Cx32128L) resulted in the adoption of the trafficking properties of Cx26 as well as its unusual post-translational membrane integration characteristics. The results indicate that multiple intracellular connexin trafficking routes exist and provide a further mechanism for regulating the connexin composition of gap junctions and thus specificity in intercellular signalling.
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Affiliation(s)
- P E Martin
- Wales Heart Research Institute and Department of Medical Biochemistry, University of Wales College of Medicine, Cardiff, UK.
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Abstract
The enteric pathogen Vibrio cholerae secretes a water-soluble 80-kD cytolysin, Vibrio cholerae cytolysin (VCC) that assembles into pentameric channels following proteolytic activation by exogenous proteases. Until now, VCC has been placed in a unique class of pore-forming toxins, distinct from paradigms such as Staphyloccal alpha-hemolysin. However, as reported here, amino acid sequence analysis and three-dimensional structure modeling indicate that the core component of the VCC toxin is related in sequence and structure to a family of hemolysins from Staphylococcus aureus that include leukocidin F and alpha-hemolysin. Furthermore, our analysis has identified the channel-forming region of VCC and a potential lipid head-group binding site, and suggests a conserved mechanism of assembly and lysis. An additional domain in the VCC toxin is related to plant lectins, conferring additional target cell specificity to the toxin.
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Affiliation(s)
- Rich Olson
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032, USA
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40
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Nguyen VT, Higuchi H, Kamio Y. Controlling pore assembly of staphylococcal gamma-haemolysin by low temperature and by disulphide bond formation in double-cysteine LukF mutants. Mol Microbiol 2002; 45:1485-98. [PMID: 12354220 DOI: 10.1046/j.1365-2958.2002.03125.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Staphylococcal LukF and Hlg2 are water-soluble monomers of gamma-haemolysin that assemble into oligomeric pores on the erythrocyte membranes. Here, we have created double-cysteine LukF mutants, in which single disulphide bonds connect either the prestem domain and the cap domain (V12C-T136C, Cap-Stem), or two beta-strands within the prestem domain (T117C-T136C, Stem-Stem) to control pore assembly of gamma-haemolysin at intermediate stages. The disulphide-trapped mutants were inactive in erythrocyte lysis, but gained full haemolytic activity if the disulphide bonds were reduced. The disulphide bonds blocked neither the membrane binding ability nor the intermediate prepore oligomerization, but efficiently inhibited the transition from prepores to pores. The prepores of Cap-Stem were dissociated into monomers in 1% SDS. In contrast, the prepores of Stem-Stem were stable in SDS and had ring-shaped structures similar to those of wild-type LukF, as observed by transmission electron microscopy. The transition of both mutants from prepores to pores could even be achieved by reducing disulphide bonds at low temperature (2 degrees C), whereas prepore oligomerization was effectively inhibited by low temperature. Finally, real-time transition of Stem-Stem from prepores to pores on ghost cells, visualized using a Ca2+-sensitive fluorescent indicator (Rhod2), was shown by the sequential appearance of fluorescence spots, indicating pore-opening events. Taken together, these data indicate that the prepores are legitimate intermediates during gamma-haemolysin pore assembly, and that conformational changes around residues 117 and 136 of the prestem domain are essential for pore formation, but not for membrane binding or prepore oligomerization. We propose a mechanism for gamma-haemolysin pore assembly based on the demonstrated intermediates.
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Affiliation(s)
- Vananh T Nguyen
- Department of Molecular and Cell Biology, School of Agricultural Science, Tohoku University, Sendai, Japan
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41
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Ahmad S, Evans WH. Post-translational integration and oligomerization of connexin 26 in plasma membranes and evidence of formation of membrane pores: implications for the assembly of gap junctions. Biochem J 2002; 365:693-9. [PMID: 11985493 PMCID: PMC1222727 DOI: 10.1042/bj20011572] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2001] [Revised: 04/26/2002] [Accepted: 05/02/2002] [Indexed: 01/13/2023]
Abstract
Gap-junction channels provide a widespread intercellular signalling mechanism. They are constructed of a family of connexin membrane proteins that thread across the membrane four times and oligomerize to generate hexameric gap-junction hemichannels. Using an in vitro cell-free transcription/translation system, we demonstrate that connexin (Cx) 26, one of the smallest connexins, is integrated directly in a post-translational manner into plasma membranes. Protein-cleavage studies of Cx26 integrated into plasma membranes indicate a similar native transmembrane topography to that of Cx26 integrated co-translationally into microsomes. Cx26 integrated post-translationally into plasma membranes oligomerizes and, when incorporated into liposomes, provides permeability to ascorbic acid, suggesting that gap-junction hemichannels are generated. The results provide the basis of a novel alternative mechanism for spontaneous assembly in plasma membranes of Cx26 gap-junction hemichannels that occurs independently of the conventional biogenesis of gap junctions involving connexin trafficking and oligomerization via membrane components of the secretory pathway.
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Affiliation(s)
- Shoeb Ahmad
- Department of Medical Biochemistry, University of Wales College of Medicine, Heath Park, Cardiff CF14 4XN, Wales, U.K
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42
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Miles G, Bayley H, Cheley S. Properties of Bacillus cereus hemolysin II: a heptameric transmembrane pore. Protein Sci 2002; 11:1813-24. [PMID: 12070333 PMCID: PMC2373656 DOI: 10.1110/ps.0204002] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
Abstract
The gene encoding hemolysin II (HlyII) was amplified from Bacillus cereus genomic DNA and a truncated mutant, HlyII(DeltaCT), was constructed lacking the 94 amino acid extension at the C terminus. The proteins were produced in an E. coli cell-free in vitro transcription and translation system, and were shown to assemble into SDS-stable oligomers on rabbit erythrocyte membranes and liposomes. The hemolytic activity of HlyII was measured with rabbit erythrocytes yielding an HC(50) value of 1.64 ng mL(-1), which is over 15 times more potent than staphylococcal alpha-hemolysin. HlyII(DeltaCT) was about eight times less potent than HlyII in this assay. Limited proteolysis of the oligomers formed by HlyII and HlyII(DeltaCT) on red cell membranes showed that the C-terminal extension is sensitive to digestion, while HlyII(DeltaCT) is protease resistant and migrates with an electrophoretic mobility similar to that of digested HlyII. HlyII forms moderately anion selective, rectifying pores (I(+80)/I(-80) = 0.57, 1 M KCl, pH 7.4) in planar lipid bilayers of diphytanoylphosphatidylcholine with a unitary conductance of 637 pS (1 M KCl, 5 mM HEPES, pH 7.4) and exhibits no gating over a wide range of applied potentials (-160 to +160 mV). In addition, it was demonstrated that HlyII forms a homoheptameric pore by using gel shift electrophoresis aided by a genetically encoded oligoaspartate tag. Although they share limited primary sequence identity (30%), these data confirm that HlyII is a structural and functional homolog of staphylococcal alpha-hemolysin.
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Affiliation(s)
- George Miles
- Department of Medical Biochemistry & Genetics, The Texas A&M University System Health Science Center, 440 Reynolds Medical Building, College Station, TX 77843-1114, USA
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43
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Comai M, Dalla Serra M, Coraiola M, Werner S, Colin DA, Monteil H, Prévost G, Menestrina G. Protein engineering modulates the transport properties and ion selectivity of the pores formed by staphylococcal gamma-haemolysins in lipid membranes. Mol Microbiol 2002; 44:1251-67. [PMID: 12068809 DOI: 10.1046/j.1365-2958.2002.02943.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Staphylococcal gamma-haemolysins are bicomponent toxins in a family including other leucocidins and alpha-toxin. Two active toxins are formed combining HlgA or HlgC with HlgB. Both open pores in lipid membranes with conductance, current voltage characteristics and stability similar to alpha-toxin, but different selectivity (cation instead of anion). Structural analogies between gamma-haemolysins and alpha-toxin indicate the presence, at the pore entry, of a conserved region containing four positive charges in alpha-toxin, but either positive or negative in gamma-haemolysins. Four mutants were produced (HlgA D44K, HlgB D47K, HlgB D49K and HlgB D47K/D49K) converting those negative charges to positive in HlgA and HlgB. When all charges were positive, the pores had the same selectivity and conductance as alpha-toxin, suggesting that the cluster may form an entrance electrostatic filter. As mutated HlgC-HlgB pores were less affected, additional charges in the lumen of the pore were changed (HlgB E107Q, HlgB D121N, HlgB T136D and HlgA K108T). Removing a negative charge from the lumen made the selectivity of both HlgA-HlgB D121N and HlgC-HlgB D121N more anionic. Residue D121 of HlgB is compensated by a positive residue (HlgA K108) in the HlgA-HlgB pore, but isolated in the more cation-selective HlgC-HlgB pore. Interestingly, the pore formed by HlgA K108T-HlgB, in which the positive charge of HlgA was removed, was as cation selective as HlgC-HlgB. Meanwhile, the pore formed by HlgA K108T-HlgB D121N, in which the two charge changes compensated, retrieved the properties of wild-type HlgA-HlgB. We conclude that the conductance and selectivity of the gamma-haemolysin pores depend substantially on the presence and location of charged residues in the channel.
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Affiliation(s)
- Massimiliano Comai
- CNR-ITC Centro di Fisica degli Stati Aggregati, Istituto di Biofisica del CNR, Via Sommarive 18, I-38050 Povo (Trento), Italy
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Miles G, Movileanu L, Bayley H. Subunit composition of a bicomponent toxin: staphylococcal leukocidin forms an octameric transmembrane pore. Protein Sci 2002; 11:894-902. [PMID: 11910032 PMCID: PMC2373538 DOI: 10.1110/ps.4360102] [Citation(s) in RCA: 104] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Staphylococcal leukocidin pores are formed by the obligatory interaction of two distinct polypeptides, one of class F and one of class S, making them unique in the family of beta-barrel pore-forming toxins (beta-PFTs). By contrast, other beta-PFTs form homo-oligomeric pores; for example, the staphylococcal alpha-hemolysin (alpha HL) pore is a homoheptamer. Here, we deduce the subunit composition of a leukocidin pore by two independent methods: gel shift electrophoresis and site-specific chemical modification during single-channel recording. Four LukF and four LukS subunits coassemble to form an octamer. This result in part explains properties of the leukocidin pore, such as its high conductance compared to the alpha HL pore. It is also pertinent to the mechanism of assembly of beta-PFT pores and suggests new possibilities for engineering these proteins.
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Affiliation(s)
- George Miles
- Department of Medical Biochemistry and Genetics, The Texas A&M University System Health Science Center, College Station, Texas 77843-1114, USA
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