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Yvon M, German TL, Ullman DE, Dasgupta R, Parker MH, Ben-Mahmoud S, Verdin E, Gognalons P, Ancelin A, Laï Kee Him J, Girard J, Vernerey MS, Fernandez E, Filloux D, Roumagnac P, Bron P, Michalakis Y, Blanc S. The genome of a bunyavirus cannot be defined at the level of the viral particle but only at the scale of the viral population. Proc Natl Acad Sci U S A 2023; 120:e2309412120. [PMID: 37983500 PMCID: PMC10691328 DOI: 10.1073/pnas.2309412120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2023] [Accepted: 10/21/2023] [Indexed: 11/22/2023] Open
Abstract
Bunyaviruses are enveloped negative or ambisense single-stranded RNA viruses with a genome divided into several segments. The canonical view depicts each viral particle packaging one copy of each genomic segment in one polarity named the viral strand. Several opposing observations revealed nonequal ratios of the segments, uneven number of segments per virion, and even packaging of viral complementary strands. Unfortunately, these observations result from studies often addressing other questions, on distinct viral species, and not using accurate quantitative methods. Hence, what RNA segments and strands are packaged as the genome of any bunyavirus remains largely ambiguous. We addressed this issue by first investigating the virion size distribution and RNA content in populations of the tomato spotted wilt virus (TSWV) using microscopy and tomography. These revealed heterogeneity in viral particle volume and amount of RNA content, with a surprising lack of correlation between the two. Then, the ratios of all genomic segments and strands were established using RNA sequencing and qRT-PCR. Within virions, both plus and minus strands (but no mRNA) are packaged for each of the three L, M, and S segments, in reproducible nonequimolar proportions determined by those in total cell extracts. These results show that virions differ in their genomic content but together build up a highly reproducible genetic composition of the viral population. This resembles the genome formula described for multipartite viruses, with which some species of the order Bunyavirales may share some aspects of the way of life, particularly emerging properties at a supravirion scale.
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Affiliation(s)
- Michel Yvon
- PHIM, Univ Montpellier, INRAE, CIRAD, IRD, Institut Agro, Montpellier34398, France
| | - Thomas L. German
- Department of Entomology, University of Wisconsin, Wisconsin53706, Madison
| | - Diane E. Ullman
- Department of Entomology and Nematology, University of California, California95616, Davis
| | - Ranjit Dasgupta
- Department of Entomology, University of Wisconsin, Wisconsin53706, Madison
| | - Maxwell H. Parker
- Department of Entomology, University of Wisconsin, Wisconsin53706, Madison
| | - Sulley Ben-Mahmoud
- Department of Entomology and Nematology, University of California, California95616, Davis
| | - Eric Verdin
- Pathologie végétale, INRAE, Avignon84143, France
| | | | - Aurélie Ancelin
- CBS, Univ Montpellier, CNRS, INSERM, Montpellier34090, France
| | | | - Justine Girard
- CBS, Univ Montpellier, CNRS, INSERM, Montpellier34090, France
| | | | - Emmanuel Fernandez
- PHIM, Univ Montpellier, INRAE, CIRAD, IRD, Institut Agro, Montpellier34398, France
| | - Denis Filloux
- PHIM, Univ Montpellier, INRAE, CIRAD, IRD, Institut Agro, Montpellier34398, France
| | - Philippe Roumagnac
- PHIM, Univ Montpellier, INRAE, CIRAD, IRD, Institut Agro, Montpellier34398, France
| | - Patrick Bron
- CBS, Univ Montpellier, CNRS, INSERM, Montpellier34090, France
| | | | - Stéphane Blanc
- PHIM, Univ Montpellier, INRAE, CIRAD, IRD, Institut Agro, Montpellier34398, France
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Negi G, Sharma A, Dey M, Dhanawat G, Parveen N. Membrane attachment and fusion of HIV-1, influenza A, and SARS-CoV-2: resolving the mechanisms with biophysical methods. Biophys Rev 2022; 14:1109-1140. [PMID: 36249860 PMCID: PMC9552142 DOI: 10.1007/s12551-022-00999-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Accepted: 09/16/2022] [Indexed: 10/31/2022] Open
Abstract
Attachment to and fusion with cell membranes are two major steps in the replication cycle of many human viruses. We focus on these steps for three enveloped viruses, i.e., HIV-1, IAVs, and SARS-CoV-2. Viral spike proteins drive the membrane attachment and fusion of these viruses. Dynamic interactions between the spike proteins and membrane receptors trigger their specific attachment to the plasma membrane of host cells. A single virion on cell membranes can engage in binding with multiple receptors of the same or different types. Such dynamic and multivalent binding of these viruses result in an optimal attachment strength which in turn leads to their cellular entry and membrane fusion. The latter process is driven by conformational changes of the spike proteins which are also class I fusion proteins, providing the energetics of membrane tethering, bending, and fusion. These viruses exploit cellular and membrane factors in regulating the conformation changes and membrane processes. Herein, we describe the major structural and functional features of spike proteins of the enveloped viruses including highlights on their structural dynamics. The review delves into some of the case studies in the literature discussing the findings on multivalent binding, membrane hemifusion, and fusion of these viruses. The focus is on applications of biophysical tools with an emphasis on single-particle methods for evaluating mechanisms of these processes at the molecular and cellular levels.
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Affiliation(s)
- Geetanjali Negi
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, India
| | - Anurag Sharma
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, India
| | - Manorama Dey
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, India
| | - Garvita Dhanawat
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, India
| | - Nagma Parveen
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, India
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Qiao Y, Yang M, Marabella IA, McGee DA, Olson BA, Torremorell M, Hogan CJ. Wind tunnel-based testing of a photoelectrochemical oxidative filter-based air purification unit in coronavirus and influenza aerosol removal and inactivation. INDOOR AIR 2021; 31:2058-2069. [PMID: 33960547 PMCID: PMC8242653 DOI: 10.1111/ina.12847] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2021] [Revised: 03/17/2021] [Accepted: 04/12/2021] [Indexed: 05/27/2023]
Abstract
Recirculating air purification technologies are employed as potential means of reducing exposure to aerosol particles and airborne viruses. Toward improved testing of recirculating air purification units, we developed and applied a medium-scale single-pass wind tunnel test to examine the size-dependent collection of particles and the collection and inactivation of viable bovine coronavirus (BCoV, a betacoronavirus), porcine respiratory coronavirus (PRCV, an alphacoronavirus), and influenza A virus (IAV), by a commercial air purification unit. The tested unit, the Molekule Air Mini, incorporates a MERV 16 filter as well as a photoelectrochemical oxidating layer. It was found to have a collection efficiency above 95.8% for all tested particle diameters and flow rates, with collection efficiencies above 99% for supermicrometer particles with the minimum collection efficiency for particles smaller than 100 nm. For all three tested viruses, the physical tracer-based log reduction was near 2.0 (99% removal). Conversely, the viable virus log reductions were found to be near 4.0 for IAV, 3.0 for BCoV, and 2.5 for PRCV, suggesting additional inactivation in a virus family- and genus-specific manner. In total, this work describes a suite of test methods which can be used to rigorously evaluate the efficacy of recirculating air purification technologies.
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Affiliation(s)
- Yuechen Qiao
- Department of Mechanical EngineeringCollege of Science and EngineeringUniversity of MinnesotaMinneapolisMNUSA
| | - My Yang
- Department of Veterinary Population MedicineCollege of Veterinary MedicineUniversity of MinnesotaSaint PaulMNUSA
| | - Ian A. Marabella
- Department of Mechanical EngineeringCollege of Science and EngineeringUniversity of MinnesotaMinneapolisMNUSA
| | - Devin A.J. McGee
- Department of Mechanical EngineeringCollege of Science and EngineeringUniversity of MinnesotaMinneapolisMNUSA
| | - Bernard A. Olson
- Department of Mechanical EngineeringCollege of Science and EngineeringUniversity of MinnesotaMinneapolisMNUSA
| | - Montserrat Torremorell
- Department of Veterinary Population MedicineCollege of Veterinary MedicineUniversity of MinnesotaSaint PaulMNUSA
| | - Christopher J. Hogan
- Department of Mechanical EngineeringCollege of Science and EngineeringUniversity of MinnesotaMinneapolisMNUSA
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Abstract
Herpesviruses are an extensive family of double-stranded DNA-containing animal viruses. The typical herpes-virion consists of a loosely-fitting envelope derived from the nuclear membrane of the host cell, within which a proteinaceous "tegument" layer encloses an icosahedral nucleocapsid. The capsid is a thick-walled shell of triangulation class T=16, whose major constituent is a protein of monomer mass ∽ 155kDa. Hexamers of this protein occupy the hexavalent sites of the icosahedral surface lattice. The nucleocapsid also contains several minor proteins and the linear genome of 80-150 MDaDespite investigations extending over more than 20 years, many basic questions concerning the HSV nucleocapsid structure remain unanswered; e.g. where are the minor proteins located? and what is the structure and chemical identity of the vertex capsomers? Moreover, although several models have been proposed for the packing of DNA inside the capsid, further, more detailed, evidence is needed to settle this issue. Conventional electron microscopic approaches having been constrained by difficulties in preserving and conveying the native structures of intact nucleocapsids, we have started to explore the potentialities of cryo-electron microscopy for this system.
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5
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Rapid functionalisation and detection of viruses via a novel Ca 2+-mediated virus-DNA interaction. Sci Rep 2019; 9:16219. [PMID: 31700064 PMCID: PMC6838052 DOI: 10.1038/s41598-019-52759-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Accepted: 10/22/2019] [Indexed: 11/28/2022] Open
Abstract
Current virus detection methods often take significant time or can be limited in sensitivity and specificity. The increasing frequency and magnitude of viral outbreaks in recent decades has resulted in an urgent need for diagnostic methods that are facile, sensitive, rapid and inexpensive. Here, we describe and characterise a novel, calcium-mediated interaction of the surface of enveloped viruses with DNA, that can be used for the functionalisation of intact virus particles via chemical groups attached to the DNA. Using DNA modified with fluorophores, we have demonstrated the rapid and sensitive labelling and detection of influenza and other viruses using single-particle tracking and particle-size determination. With this method, we have detected clinical isolates of influenza in just one minute, significantly faster than existing rapid diagnostic tests. This powerful technique is easily extendable to a wide range of other enveloped pathogenic viruses and holds significant promise as a future diagnostic tool.
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Gallagher JR, McCraw DM, Torian U, Gulati NM, Myers ML, Conlon MT, Harris AK. Characterization of Hemagglutinin Antigens on Influenza Virus and within Vaccines Using Electron Microscopy. Vaccines (Basel) 2018; 6:E31. [PMID: 29799445 PMCID: PMC6027289 DOI: 10.3390/vaccines6020031] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2018] [Revised: 05/11/2018] [Accepted: 05/21/2018] [Indexed: 01/08/2023] Open
Abstract
Influenza viruses affect millions of people worldwide on an annual basis. Although vaccines are available, influenza still causes significant human mortality and morbidity. Vaccines target the major influenza surface glycoprotein hemagglutinin (HA). However, circulating HA subtypes undergo continual variation in their dominant epitopes, requiring vaccines to be updated annually. A goal of next-generation influenza vaccine research is to produce broader protective immunity against the different types, subtypes, and strains of influenza viruses. One emerging strategy is to focus the immune response away from variable epitopes, and instead target the conserved stem region of HA. To increase the display and immunogenicity of the HA stem, nanoparticles are being developed to display epitopes in a controlled spatial arrangement to improve immunogenicity and elicit protective immune responses. Engineering of these nanoparticles requires structure-guided design to optimize the fidelity and valency of antigen presentation. Here, we review electron microscopy applied to study the 3D structures of influenza viruses and different vaccine antigens. Structure-guided information from electron microscopy should be integrated into pipelines for the development of both more efficacious seasonal and universal influenza vaccine antigens. The lessons learned from influenza vaccine electron microscopic research could aid in the development of novel vaccines for other pathogens.
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Affiliation(s)
- John R Gallagher
- Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 50 South Drive, Room 6351, Bethesda, MD 20892, USA.
| | - Dustin M McCraw
- Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 50 South Drive, Room 6351, Bethesda, MD 20892, USA.
| | - Udana Torian
- Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 50 South Drive, Room 6351, Bethesda, MD 20892, USA.
| | - Neetu M Gulati
- Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 50 South Drive, Room 6351, Bethesda, MD 20892, USA.
| | - Mallory L Myers
- Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 50 South Drive, Room 6351, Bethesda, MD 20892, USA.
| | - Michael T Conlon
- Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 50 South Drive, Room 6351, Bethesda, MD 20892, USA.
| | - Audray K Harris
- Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 50 South Drive, Room 6351, Bethesda, MD 20892, USA.
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7
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Morphological characterization of a plant-made virus-like particle vaccine bearing influenza virus hemagglutinins by electron microscopy. Vaccine 2018; 36:2147-2154. [PMID: 29550194 DOI: 10.1016/j.vaccine.2018.02.106] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Revised: 02/19/2018] [Accepted: 02/23/2018] [Indexed: 12/17/2022]
Abstract
Plant-made virus-like particle (VLP) vaccines that display wild-type influenza hemagglutinin (HA) are rapidly advancing through clinical trials. Produced by transient transfection of Nicotiana benthamiana, these novel vaccines are unusually immunogenic, eliciting both humoral and cellular responses. Here, we directly visualized VLPs bearing either HA trimers derived from strains A/California/7/2009 or A/Indonesia/5/05 using cryo-electron microscopy and determined the 3D organization of the VLPs using cryo-electron tomography. More than 99.9% of the HA trimers in the vaccine preparations were found on discoid and ovoid-shaped particles. The discoid-shaped VLPs presented HA trimers on their outer diameter. The ovoid-shaped VLPs contained HA trimers evenly distributed at their surface. The VLPs were stable for 12 months at 4 °C. Early interactions of the VLPs with mouse dendritic and human monocytoid (U-937) cells were visualized by electron microscopy after resin-embedding and sectioning. The VLP particles were observed bound to plasma membranes as well as inside vesicles. Mouse dendritic cells exposed to VLPs displayed classic morphological changes associated with activation including the extensive formation of dendrites. Our findings demonstrate that plant-made VLPs bearing influenza HA trimers are morphologically stable over time and raise the possibility that these VLPs may interact with and activate antigen-presenting cells in a manner similar to the intact virus.
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8
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Structural analysis of the complex between influenza B nucleoprotein and human importin-α. Sci Rep 2017; 7:17164. [PMID: 29215074 PMCID: PMC5719345 DOI: 10.1038/s41598-017-17458-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Accepted: 11/27/2017] [Indexed: 12/29/2022] Open
Abstract
Influenza viruses are negative strand RNA viruses that replicate in the nucleus of the cell. The viral nucleoprotein (NP) is the major component of the viral ribonucleoprotein. In this paper we show that the NP of influenza B has a long N-terminal tail of 70 residues with intrinsic flexibility. This tail contains the Nuclear Location Signal (NLS). The nuclear trafficking of the viral components mobilizes cellular import factors at different stages, making these host-pathogen interactions promising targets for new therapeutics. NP is imported into the nucleus by the importin-α/β pathway, through a direct interaction with importin-α isoforms. Here we provide a combined nuclear magnetic resonance and small-angle X-ray scattering (NMR/SAXS) analysis to describe the dynamics of the interaction between influenza B NP and the human importin-α. The NP of influenza B does not have a single NLS nor a bipartite NLS but our results suggest that the tail harbors several adjacent NLS sequences, located between residues 30 and 71.
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9
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The Interplay between the Host Receptor and Influenza Virus Hemagglutinin and Neuraminidase. Int J Mol Sci 2017; 18:ijms18071541. [PMID: 28714909 PMCID: PMC5536029 DOI: 10.3390/ijms18071541] [Citation(s) in RCA: 117] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Revised: 06/30/2017] [Accepted: 07/10/2017] [Indexed: 12/16/2022] Open
Abstract
The hemagglutinin (HA) and neuraminidase (NA) glycoproteins of influenza A virus are responsible for the surface interactions of the virion with the host. Entry of the virus is mediated by functions of the HA: binding to cellular receptors and facilitating fusion of the virion membrane with the endosomal membrane. The HA structure contains receptor binding sites in the globular membrane distal head domains of the trimer, and the fusion machinery resides in the stem region. These sites have specific characteristics associated with subtype and host, and the differences often define species barriers. For example, avian viruses preferentially recognize α2,3-Sialic acid terminating glycans as receptors and mammalian viruses recognize α2,6-Sialic acid. The neuraminidase, or the receptor-destroying protein, cleaves the sialic acid from cellular membrane constituents and viral glycoproteins allowing for egress of nascent virions. A functional balance of activity has been demonstrated between the two glycoproteins, resulting in an optimum level of HA affinity and NA enzymatic cleavage to allow for productive infection. As more is understood about both HA and NA, the relevance for functional balance between HA and NA continues to expand, with potential implications for interspecies transmission, host adaptation, and pathogenicity.
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10
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Three-Dimensional Structural Characterization of HIV-1 Tethered to Human Cells. J Virol 2015; 90:1507-21. [PMID: 26582000 DOI: 10.1128/jvi.01880-15] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 11/14/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Tetherin (BST2, CD317, or HM1.24) is a host cellular restriction factor that prevents the release of enveloped viruses by mechanically linking virions to the plasma membrane. The precise arrangement of tetherin molecules at the plasma membrane site of HIV-1 assembly, budding, and restriction is not well understood. To gain insight into the biophysical mechanism underlying tetherin-mediated restriction of HIV-1, we utilized cryo-electron tomography (cryo-ET) to directly visualize HIV-1 virus-like particles (VLPs) and virions tethered to human cells in three dimensions (3D). Rod-like densities that we refer to as tethers were seen connecting HIV-1 virions to each other and to the plasma membrane. Native immunogold labeling showed tetherin molecules located on HIV-1 VLPs and virions in positions similar to those of the densities observed by cryo-ET. The location of the tethers with respect to the ordered immature Gag lattice or mature conical core was random. However, tethers were not uniformly distributed on the viral membrane but rather formed clusters at sites of contact with the cell or other virions. Chains of tethered HIV-1 virions often were arranged in a linear fashion, primarily as single chains and, to a lesser degree, as branched chains. Distance measurements support the extended tetherin model, in which the coiled-coil ectodomains are oriented perpendicular with respect to the viral and plasma membranes. IMPORTANCE Tetherin is a cellular factor that restricts HIV-1 release by directly cross-linking the virus to the host cell plasma membrane. We used cryo-electron tomography to visualize HIV-1 tethered to human cells in 3D. We determined that tetherin-restricted HIV-1 virions were physically connected to each other or to the plasma membrane by filamentous tethers that resembled rods ∼15 nm in length, which is consistent with the extended tetherin model. In addition, we found the position of the tethers to be arbitrary relative to the ordered immature Gag lattice or the mature conical cores. However, when present as multiple copies, the tethers clustered at the interface between virions. Tethered HIV-1 virions were arranged in a linear fashion, with the majority as single chains. This study advances our understanding of tetherin-mediated HIV-1 restriction by defining the spatial arrangement and orientation of tetherin molecules at sites of HIV-1 restriction.
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11
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Young KR, Arthus-Cartier G, Yam KK, Lavoie PO, Landry N, D'Aoust MA, Vézina LP, Couture MMJ, Ward BJ. Generation and characterization of a trackable plant-made influenza H5 virus-like particle (VLP) containing enhanced green fluorescent protein (eGFP). FASEB J 2015; 29:3817-27. [PMID: 26038124 DOI: 10.1096/fj.15-270421] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Accepted: 05/18/2015] [Indexed: 12/17/2022]
Abstract
Medicago, Inc. has developed an efficient virus-like particle (VLP) vaccine production platform using the Nicotiana benthamiana expression system, and currently has influenza-based products targeting seasonal/pandemic hemagglutinin (HA) proteins in advanced clinical trials. We wished to generate a trackable HA-based VLP that would allow us to study both particle assembly in plants and VLP interactions within the mammalian immune system. To this end, a fusion protein was designed, composed of H5 (from influenza A/Indonesia/05/2005 [H5N1]) with enhanced green fluorescent protein (eGFP). Expression of H5-eGFP in N. benthamiana produced brightly fluorescent ∼160 nm particles resembling H5-VLPs. H5-eGFP-VLPs elicited anti-H5 serologic responses in mice comparable to those elicited by H5-VLPs in almost all assays tested (hemagglutination inhibition/IgG(total)/IgG1/IgG2b/IgG2a:IgG1 ratio), as well as a superior anti-GFP IgG response (mean optical density = 2.52 ± 0.16 sem) to that elicited by soluble GFP (mean optical density = 0.12 ± 0.06 sem). Confocal imaging of N. benthamiana cells expressing H5-eGFP displayed large fluorescent accumulations at the cell periphery, and draining lymph nodes from mice given H5-eGFP-VLPs via footpad injection demonstrated bright fluorescence shortly after administration (10 min), providing proof of concept that the H5-eGFP-protein/VLPs could be used to monitor both VLP assembly and immune trafficking. Given these findings, this novel fluorescent reagent will be a powerful tool to gain further fundamental insight into the biology of influenza VLP vaccines.
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Affiliation(s)
- Katie R Young
- *Research Institute of McGill University Health Centre and Department of Experimental Medicine, McGill University, Montréal, Québec, Canada; and Medicago, Incorporated, Québec, Québec, Canada
| | - Guillaume Arthus-Cartier
- *Research Institute of McGill University Health Centre and Department of Experimental Medicine, McGill University, Montréal, Québec, Canada; and Medicago, Incorporated, Québec, Québec, Canada
| | - Karen K Yam
- *Research Institute of McGill University Health Centre and Department of Experimental Medicine, McGill University, Montréal, Québec, Canada; and Medicago, Incorporated, Québec, Québec, Canada
| | - Pierre-Olivier Lavoie
- *Research Institute of McGill University Health Centre and Department of Experimental Medicine, McGill University, Montréal, Québec, Canada; and Medicago, Incorporated, Québec, Québec, Canada
| | - Nathalie Landry
- *Research Institute of McGill University Health Centre and Department of Experimental Medicine, McGill University, Montréal, Québec, Canada; and Medicago, Incorporated, Québec, Québec, Canada
| | - Marc-André D'Aoust
- *Research Institute of McGill University Health Centre and Department of Experimental Medicine, McGill University, Montréal, Québec, Canada; and Medicago, Incorporated, Québec, Québec, Canada
| | - Louis-Philippe Vézina
- *Research Institute of McGill University Health Centre and Department of Experimental Medicine, McGill University, Montréal, Québec, Canada; and Medicago, Incorporated, Québec, Québec, Canada
| | - Manon M-J Couture
- *Research Institute of McGill University Health Centre and Department of Experimental Medicine, McGill University, Montréal, Québec, Canada; and Medicago, Incorporated, Québec, Québec, Canada
| | - Brian J Ward
- *Research Institute of McGill University Health Centre and Department of Experimental Medicine, McGill University, Montréal, Québec, Canada; and Medicago, Incorporated, Québec, Québec, Canada
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Structural Analysis of the Roles of Influenza A Virus Membrane-Associated Proteins in Assembly and Morphology. J Virol 2015; 89:8957-66. [PMID: 26085153 DOI: 10.1128/jvi.00592-15] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Accepted: 06/09/2015] [Indexed: 01/30/2023] Open
Abstract
UNLABELLED The assembly of influenza A virus at the plasma membrane of infected cells leads to release of enveloped virions that are typically round in tissue culture-adapted strains but filamentous in strains isolated from patients. The viral proteins hemagglutinin (HA), neuraminidase (NA), matrix protein 1 (M1), and M2 ion channel all contribute to virus assembly. When expressed individually or in combination in cells, they can all, under certain conditions, mediate release of membrane-enveloped particles, but their relative roles in virus assembly, release, and morphology remain unclear. To investigate these roles, we produced membrane-enveloped particles by plasmid-derived expression of combinations of HA, NA, and M proteins (M1 and M2) or by infection with influenza A virus. We monitored particle release, particle morphology, and plasma membrane morphology by using biochemical methods, electron microscopy, electron tomography, and cryo-electron tomography. Our data suggest that HA, NA, or HANA (HA plus NA) expression leads to particle release through nonspecific induction of membrane curvature. In contrast, coexpression with the M proteins clusters the glycoproteins into filamentous membrane protrusions, which can be released as particles by formation of a constricted neck at the base. HA and NA are preferentially distributed to differently curved membranes within these particles. Both the budding intermediates and the released particles are morphologically similar to those produced during infection with influenza A virus. Together, our data provide new insights into influenza virus assembly and show that the M segment together with either of the glycoproteins is the minimal requirement to assemble and release membrane-enveloped particles that are truly virus-like. IMPORTANCE Influenza A virus is a major respiratory pathogen. It assembles membrane-enveloped virus particles whose shapes vary from spherical to filamentous. Here we examine the roles of individual viral proteins in mediating virus assembly and determining virus shape. To do this, we used a range of electron microscopy techniques to obtain and compare two- and three-dimensional images of virus particles and virus-like particles during and after assembly. The virus-like particles were produced using different combinations of viral proteins. Among our results, we found that coexpression of one or both of the viral surface proteins (hemagglutinin and neuraminidase) with the viral membrane-associated proteins encoded by the M segment results in assembly and release of filamentous virus-like particles in a manner very similar to that of the budding and release of influenza virions. These data provide novel insights into the roles played by individual viral proteins in influenza A virus assembly.
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13
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Fontana J, Steven AC. Influenza virus-mediated membrane fusion: Structural insights from electron microscopy. Arch Biochem Biophys 2015; 581:86-97. [PMID: 25958107 DOI: 10.1016/j.abb.2015.04.011] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Revised: 04/21/2015] [Accepted: 04/27/2015] [Indexed: 12/26/2022]
Abstract
Influenza virus, the causative agent of flu, enters the host cell by endocytosis. The low pH encountered inside endosomes triggers conformational changes in the viral glycoprotein hemagglutinin (HA), that mediate fusion of the viral and cellular membranes. This releases the viral genome into the cytoplasm of the infected cell, establishing the onset of the replication cycle. To investigate the structural basis of HA-mediated membrane fusion, a number of techniques have been employed. These include X-ray crystallography, which has provided atomic models of the HA ectodomain in its initial (pre-fusion) state and of part of HA in its final (post-fusion) state. However, this left an information deficit concerning many other aspects of the fusion process. Electron microscopy (EM) approaches are helping to fill this void. For example, influenza virions at neutral pH have been imaged by cryo-EM and cryo-electron tomography (cryo-ET); thin section EM has shown that influenza viruses enter the cell by endocytosis; the large-scale structural changes in HA when virions are exposed to low pH (pre-fusion to post-fusion states) have been visualized by negative staining and cryo-EM; acidification also induces structural changes in the M1 matrix layer and its separation from the viral envelope; intermediate HA conformations between its pre- and post-fusion states have been detected by cryo-ET supplemented with subtomogram averaging; and fusion of influenza virions with liposomes has been visualized by cryo-ET. In this review, we survey EM-based contributions towards the characterization of influenza virus-mediated membrane fusion and anticipate the potential for future developments.
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Affiliation(s)
- Juan Fontana
- Laboratory of Structural Biology Research, National Institute of Arthritis, Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Alasdair C Steven
- Laboratory of Structural Biology Research, National Institute of Arthritis, Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
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Hutchinson EC, Charles PD, Hester SS, Thomas B, Trudgian D, Martínez-Alonso M, Fodor E. Conserved and host-specific features of influenza virion architecture. Nat Commun 2014; 5:4816. [PMID: 25226414 PMCID: PMC4167602 DOI: 10.1038/ncomms5816] [Citation(s) in RCA: 192] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2014] [Accepted: 07/28/2014] [Indexed: 01/11/2023] Open
Abstract
Viruses use virions to spread between hosts, and virion composition is therefore the primary determinant of viral transmissibility and immunogenicity. However, the virions of many viruses are complex and pleomorphic, making them difficult to analyse in detail. Here we address this by identifying and quantifying virion proteins with mass spectrometry, producing a complete and quantified model of the hundreds of viral and host-encoded proteins that make up the pleomorphic virions of influenza viruses. We show that a conserved influenza virion architecture is maintained across diverse combinations of virus and host. This ‘core’ architecture, which includes substantial quantities of host proteins as well as the viral protein NS1, is elaborated with abundant host-dependent features. As a result, influenza virions produced by mammalian and avian hosts have distinct protein compositions. Finally we note that influenza virions share an underlying protein composition with exosomes, suggesting that influenza virions form by subverting microvesicle production.
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Affiliation(s)
- Edward C Hutchinson
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Philip D Charles
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Svenja S Hester
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Benjamin Thomas
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - David Trudgian
- 1] Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK [2]
| | - Mónica Martínez-Alonso
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Ervin Fodor
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
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Katz G, Benkarroum Y, Wei H, Rice WJ, Bucher D, Alimova A, Katz A, Klukowska J, Herman GT, Gottlieb P. Morphology of influenza B/Lee/40 determined by cryo-electron microscopy. PLoS One 2014; 9:e88288. [PMID: 24516628 PMCID: PMC3916419 DOI: 10.1371/journal.pone.0088288] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2013] [Accepted: 01/07/2014] [Indexed: 12/22/2022] Open
Abstract
Cryo-electron microscopy projection image analysis and tomography is used to describe the overall architecture of influenza B/Lee/40. Algebraic reconstruction techniques with utilization of volume elements (blobs) are employed to reconstruct tomograms of this pleomorphic virus and distinguish viral surface spikes. The purpose of this research is to examine the architecture of influenza type B virions by cryo-electron tomography and projection image analysis. The aims are to explore the degree of ribonucleoprotein disorder in irregular shaped virions; and to quantify the number and distribution of glycoprotein surface spikes (hemagglutinin and neuraminidase) on influenza B. Projection image analysis of virion morphology shows that the majority (∼83%) of virions are spherical with an average diameter of 134±19 nm. The aspherical virions are larger (average diameter = 155±47 nm), exhibit disruption of the ribonucleoproteins, and show a partial loss of surface protein spikes. A count of glycoprotein spikes indicates that a typical 130 nm diameter type B virion contains ∼460 surface spikes. Configuration of the ribonucleoproteins and surface glycoprotein spikes are visualized in tomogram reconstructions and EM densities visualize extensions of the spikes into the matrix. The importance of the viral matrix in organization of virus structure through interaction with the ribonucleoproteins and the anchoring of the glycoprotein spikes to the matrix is demonstrated.
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Affiliation(s)
- Garrett Katz
- Department of Microbiology and Immunology, Sophie Davis School of Biomedical Education, The City College of New York, New York, New York, United States of America
| | - Younes Benkarroum
- Department of Computer Science, The Graduate Center, City University of New York, New York, New York, United States of America
| | - Hui Wei
- Department of Microbiology and Immunology, Sophie Davis School of Biomedical Education, The City College of New York, New York, New York, United States of America
| | - William J. Rice
- The New York Structural Biology Center, New York, New York, United States of America
| | - Doris Bucher
- Department of Microbiology and Immunology, New York Medical College, Valhalla, New York, United States of America
| | - Alexandra Alimova
- Department of Microbiology and Immunology, Sophie Davis School of Biomedical Education, The City College of New York, New York, New York, United States of America
| | - Al Katz
- Department of Physics, The City College of New York, New York, New York, United States of America
| | - Joanna Klukowska
- Department of Computer Science, The Graduate Center, City University of New York, New York, New York, United States of America
| | - Gabor T. Herman
- Department of Computer Science, The Graduate Center, City University of New York, New York, New York, United States of America
| | - Paul Gottlieb
- Department of Microbiology and Immunology, Sophie Davis School of Biomedical Education, The City College of New York, New York, New York, United States of America
- * E-mail:
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Fera A, Farrington JE, Zimmerberg J, Reese TS. A negative stain for electron microscopic tomography. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2012; 18:331-335. [PMID: 22364718 PMCID: PMC3650645 DOI: 10.1017/s1431927611012797] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
While negative staining can provide detailed, two-dimensional images of biological structures, the potential of combining tomography with negative staining to provide three-dimensional views has yet to be fully realized. Basic requirements of a negative stain for tomography are that the density and atomic number of the stain are optimal, and that the stain does not degrade or rearrange with the intensive electron dose (~10⁶ e/nm²) needed to collect a full set of tomographic images. A commercially available, tungsten-based stain appears to satisfy these prerequisites. Comparison of the surface structure of negatively stained influenza A virus with previous structural results served to evaluate this negative stain. The combination of many projections of the same structure yielded detailed images of single proteins on the viral surface. Corresponding surface renderings are a good fit to images of the viral surface derived from cryomicroscopy as well as to the shapes of crystallized surface proteins. Negative stain tomography with the appropriate stain yields detailed images of individual molecules in their normal setting on the surface of the influenza A virus.
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Affiliation(s)
- Andrea Fera
- Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Jane E. Farrington
- Laboratory of Cellular Molecular Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Joshua Zimmerberg
- Laboratory of Cellular Molecular Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Thomas S. Reese
- Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA
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Structural changes in Influenza virus at low pH characterized by cryo-electron tomography. J Virol 2012; 86:2919-29. [PMID: 22258245 DOI: 10.1128/jvi.06698-11] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Influenza virus enters host cells by endocytosis. The low pH of endosomes triggers conformational changes in hemagglutinin (HA) that mediate fusion of the viral and endosomal membranes. We have used cryo-electron tomography to visualize influenza A virus at pH 4.9, a condition known to induce fusogenicity. After 30 min, when all virions are in the postfusion state, dramatic changes in morphology are apparent: elongated particles are no longer observed, larger particles representing fused virions appear, the HA spikes become conspicuously disorganized, a layer of M1 matrix protein is no longer resolved on most virions, and the ribonucleoprotein complexes (RNPs) coagulate on the interior surface of the virion. To probe for intermediate states, preparations were imaged after 5 min at pH 4.9. These virions could be classified according to their glycoprotein arrays (organized or disorganized) and whether or not they have a resolved M1 layer. Employing subtomogram averaging, we found, in addition to the neutral-pH state of HA, two intermediate conformations that appear to reflect an outwards movement of the fusion peptide and rearrangement of the HA1 subunits, respectively. These changes are reversible. The tomograms also document pH-induced changes affecting the M1 layer that appear to render the envelope more pliable and hence conducive to fusion. However, it appears desirable for productive infection that fusion should proceed before the RNPs become coagulated with matrix protein, as eventually happens at low pH.
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Abstract
Influenza A virus is an enveloped virus with a segmented, single-strand, negative-sense RNA genome. Its virions show spherical or filamentous shapes of about 100 nm in diameter and occasionally irregular morphology, which exemplifies the pleomorphic nature of these virions. Each viral RNA segment forms a ribonucleoprotein complex (RNP), along with an RNA-dependent RNA polymerase complex and multiple copies of nucleoproteins; the RNPs reside in the enveloped virions. Here, we focus on electron microscopic analyses of influenza virions and RNPs. Based on the morphological and structural observations obtained by using electron microscopic techniques, we present a model of the native morphology of the influenza virion.
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Affiliation(s)
- Takeshi Noda
- Division of Virology, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo Tokyo, Japan
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Liu CH, Horng JT, Chang JS, Hsieh CF, Tseng YC, Lin S. Localization and force analysis at the single virus particle level using atomic force microscopy. Biochem Biophys Res Commun 2012; 417:109-15. [DOI: 10.1016/j.bbrc.2011.11.065] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2011] [Accepted: 11/14/2011] [Indexed: 11/16/2022]
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Desbat B, Lancelot E, Krell T, Nicolaï MC, Vogel F, Chevalier M, Ronzon F. Effect of the β-propiolactone treatment on the adsorption and fusion of influenza A/Brisbane/59/2007 and A/New Caledonia/20/1999 virus H1N1 on a dimyristoylphosphatidylcholine/ganglioside GM3 mixed phospholipids monolayer at the air-water interface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:13675-13683. [PMID: 21981550 DOI: 10.1021/la2027175] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The production protocol of many whole cell/virion vaccines involves an inactivation step with β-propiolactone (BPL). Despite the widespread use of BPL, its mechanism of action is poorly understood. Earlier work demonstrated that BPL alkylates nucleotide bases, but its interaction with proteins has not been studied in depth. In the present study we use ellipsometry to analyze the influence of BPL treatment of two H1N1 influenza strains, A/Brisbane/59/2007 and A/New Caledonia/20/1999, which are used for vaccine production on an industrial scale. Analyses were conducted using a mixed lipid monolayer containing ganglioside GM3, which functions as the viral receptor. Our results show that BPL treatment of both strains reduces viral affinity for the mixed monolayer and also diminishes the capacity of viral domains to self-assemble. In another series of experiments, the pH of the subphase was reduced from 7.4 to 5 to provoke the pH-induced conformational change of hemagglutinin, which occurs following endocytosis into the endosome. In the presence of the native virus the pH decrease caused a reduction in domain size, whereas lipid layer thickness and surface pressure were increased. These observations are consistent with a fusion of the viral membrane with the lipid monolayer. Importantly, this fusion was not observed with adsorbed inactivated virus, which indicates that BPL treatment inhibits the first step of virus-membrane fusion. Our data also indicate that BPL chemically modifies hemagglutinin, which mediates the interaction with GM3.
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Affiliation(s)
- Bernard Desbat
- CBMN, UMR CNRS 5248, Université Bordeaux, IPB, Allée Geoffroy Saint Hilaire 33600 Pessac, France.
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Sugita Y, Noda T, Sagara H, Kawaoka Y. Ultracentrifugation deforms unfixed influenza A virions. J Gen Virol 2011; 92:2485-2493. [PMID: 21795472 DOI: 10.1099/vir.0.036715-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Negatively stained influenza virions sometimes show irregular morphology and are often referred to as pleomorphic. However, this irregular morphology has not been visualized when ultrathin-section transmission and scanning electron microscopies are used. This study focused on the effects of ultracentrifugation on influenza A virion morphology, as negative staining often involves ultracentrifugation to concentrate or purify virions. The morphologies of unfixed, glutaraldehyde-fixed and osmium tetroxide-fixed virions were quantitatively compared before and after ultracentrifugation, and it was found that, without chemical fixation, approximately 30% of virions were altered from oval to irregular shapes following ultracentrifugation. By contrast, most glutaraldehyde-fixed virions remained uniformly elliptical, even after ultracentrifugation. When a virus with an 11 aa deletion at the C terminus of its M2 cytoplasmic tail was ultracentrifuged, its morphology was appreciably deformed compared with that of the wild-type virus. These results demonstrate that the native morphology of influenza A virions is regular but is disrupted by ultracentrifugation, and that the cytoplasmic tail of M2 is important for virion integrity.
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Affiliation(s)
- Yukihiko Sugita
- Division of Virology, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan
| | - Takeshi Noda
- Department of Special Pathogens, International Research Center for Infectious Diseases, Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan
| | - Hiroshi Sagara
- Medical Proteomics Laboratory, Institute of Medical Science, University of Tokyo, Shirokanedai, Minato-ku, Tokyo 108-8639, Japan
| | - Yoshihiro Kawaoka
- ERATO Infection-Induced Host Responses Project, Saitama 332-0012, Japan
- Division of Virology, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan
- Department of Special Pathogens, International Research Center for Infectious Diseases, Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan
- Department of Pathological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI 53706, USA
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Moulès V, Terrier O, Yver M, Riteau B, Moriscot C, Ferraris O, Julien T, Giudice E, Rolland JP, Erny A, Bouscambert-Duchamp M, Frobert E, Rosa-Calatrava M, Pu Lin Y, Hay A, Thomas D, Schoehn G, Lina B. Importance of viral genomic composition in modulating glycoprotein content on the surface of influenza virus particles. Virology 2011; 414:51-62. [PMID: 21470649 DOI: 10.1016/j.virol.2011.03.011] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2011] [Revised: 02/24/2011] [Accepted: 03/14/2011] [Indexed: 10/18/2022]
Abstract
Despite progress in our knowledge of the internal organisation of influenza virus particles, little is known about the determinants of their morphology and, more particularly, of the actual abundance of structural proteins at the virion level. To address these issues, we used cryo-EM to focus on viral (and host) factors that might account for observed differences in virion morphology and characteristics such as size, shape and glycoprotein (GP) spike density. Twelve recombinant viruses were characterised in terms of their morphology, neuraminidase activity and virus growth. The genomic composition was shown to be important in determining the GP spike density. In particular, polymerase gene segments and especially PB1/PB2 were shown to have a prominent influence in addition to that for HA in determining GP spike density, a feature consistent with a functional link between these virus components important for virus fitness.
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Affiliation(s)
- Vincent Moulès
- Université Lyon 1, Faculté de médecine RTH Laennec, CNRS FRE 3011 VirPath, Virologie et Pathologie Humaine, F-69008 Lyon, France.
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23
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Noda T, Kawaoka Y. Structure of influenza virus ribonucleoprotein complexes and their packaging into virions. Rev Med Virol 2011; 20:380-91. [PMID: 20853340 DOI: 10.1002/rmv.666] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The influenza A virus genome consists of eight segmented, single-stranded, negative-sense RNAs. Each viral RNA (vRNA) segment forms a ribonucleoprotein (RNP) complex together with NPs and a polymerase complex, which is a fundamental unit for transcription and replication of the viral genome. Although the exact structure of the intact RNP remains poorly understood, recent electron microscopic studies have revealed certain structural characteristics of the RNP. This review focuses on the findings of these various electron microscopic analyses of RNPs extracted from virions and RNPs inside virions. Based on the morphological and structural observations, we present the architecture of RNPs within a virion and discuss the genome packaging mechanism by which the vRNA segments are incorporated into virions.
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Affiliation(s)
- Takeshi Noda
- Department of Special Pathogens, International Research Center for Infectious Diseases, University of Tokyo, Tokyo, Japan.
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24
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In vitro characterization of naturally occurring influenza H3NA- viruses lacking the NA gene segment: toward a new mechanism of viral resistance? Virology 2010; 404:215-24. [PMID: 20627352 DOI: 10.1016/j.virol.2010.04.030] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2010] [Revised: 03/30/2010] [Accepted: 04/27/2010] [Indexed: 11/21/2022]
Abstract
Among a panel of 788 clinical influenza H3N2 isolates, two isolates were characterized by an oseltamivir-resistant phenotype linked to the absence of any detectable NA activity. Here, we established that the two H3NA- isolates lack any detectable full-length NA segment, and one of these could be rescued by reverse genetics in the absence of any NA segment sequence. We found that the absence of NA segment induced a moderate growth defect of the H3NA- viruses as on cultured cells. The glycoproteins density at the surface of H3NA- virions was unchanged as compared to H3N2 virions. The HA protein as well as residues 188 and 617 of the PB1 protein were shown to be strong determinants of the ability of H3NA- viruses to grow in the absence of the NA segment. The significance of these findings about naturally occurring seven-segment influenza A viruses is discussed.
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Abstract
Influenza is a lipid-enveloped, pleomorphic virus. We combine electron cryotomography and analysis of images of frozen-hydrated virions to determine the structural organization of filamentous influenza A virus. Influenza A/Udorn/72 virions are capsule-shaped or filamentous particles of highly uniform diameter. We show that the matrix layer adjacent to the membrane is an ordered helix of the M1 protein and its close interaction with the surrounding envelope determines virion morphology. The ribonucleoprotein particles (RNPs) that package the genome segments form a tapered assembly at one end of the virus interior. The neuraminidase, which is present in smaller numbers than the hemagglutinin, clusters in patches and are typically present at the end of the virion opposite to RNP attachment. Incubation of virus at low pH causes a loss of filamentous morphology, during which we observe a structural transition of the matrix layer from its helical, membrane-associated form to a multilayered coil structure inside the virus particle. The polar organization of the virus provides a model for assembly of the virion during budding at the host membrane. Images and tomograms of A/Aichi/68 X-31 virions show the generality of these conclusions to non-filamentous virions.
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26
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Hutchinson EC, von Kirchbach JC, Gog JR, Digard P. Genome packaging in influenza A virus. J Gen Virol 2009; 91:313-28. [PMID: 19955561 DOI: 10.1099/vir.0.017608-0] [Citation(s) in RCA: 213] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The negative-sense RNA genome of influenza A virus is composed of eight segments, which encode 12 proteins between them. At the final stage of viral assembly, these genomic virion (v)RNAs are incorporated into the virion as it buds from the apical plasma membrane of the cell. Genome segmentation confers evolutionary advantages on the virus, but also poses a problem during virion assembly as at least one copy of each of the eight segments is required to produce a fully infectious virus particle. Historically, arguments have been presented in favour of a specific packaging mechanism that ensures incorporation of a full genome complement, as well as for an alternative model in which segments are chosen at random but packaged in sufficient numbers to ensure that a reasonable proportion of virions are viable. The question has seen a resurgence of interest in recent years leading to a consensus that the vast majority of virions contain no more than eight segments and that a specific mechanism does indeed function to select one copy of each vRNA. This review summarizes work leading to this conclusion. In addition, we describe recent progress in identifying the specific packaging signals and discuss likely mechanisms by which these RNA elements might operate.
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Affiliation(s)
- Edward C Hutchinson
- Division of Virology, Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK
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27
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Giocondi MC, Ronzon F, Nicolai MC, Dosset P, Milhiet PE, Chevalier M, Le Grimellec C. Organization of influenza A virus envelope at neutral and low pH. J Gen Virol 2009; 91:329-38. [DOI: 10.1099/vir.0.015156-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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28
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Yamaguchi M, Danev R, Nishiyama K, Sugawara K, Nagayama K. Zernike phase contrast electron microscopy of ice-embedded influenza A virus. J Struct Biol 2008; 162:271-6. [PMID: 18313941 DOI: 10.1016/j.jsb.2008.01.009] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2007] [Revised: 12/28/2007] [Accepted: 01/17/2008] [Indexed: 11/15/2022]
Abstract
The ultrastructure of the frozen-hydrated influenza A virus was examined by Zernike phase contrast electron microscopy. Using this new microscopy, not only lipid bilayers but also individual glycoprotein spikes on viral envelopes were clearly resolved with high contrast in micrographs taken in focus. In addition to spherical and elongated virions, three other classes of virions were distinguished on the basis of the features of their viral envelope: virions with a complete matrix layer, which were the most predominant, virions with a partial matrix layer, and virions with no matrix layer under the lipid bilayer. About 450 glycoprotein spikes were present in an average-sized spherical virion. Eight ribonucleoprotein complexes, that is, a central one surrounded by seven others, were distinguished in one viral particle. Thus, Zernike phase contrast electron microscopy is a powerful tool for resolving the ultrastructure of viruses, because it enables high-contrast images of ice-embedded particles free of contrast transfer function artifacts that can be a problem in conventional cryo-electron microscopy.
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Affiliation(s)
- Masashi Yamaguchi
- Medical Mycology Research Center, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8673, Japan.
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Harris A, Cardone G, Winkler DC, Heymann JB, Brecher M, White JM, Steven AC. Influenza virus pleiomorphy characterized by cryoelectron tomography. Proc Natl Acad Sci U S A 2006; 103:19123-7. [PMID: 17146053 PMCID: PMC1748186 DOI: 10.1073/pnas.0607614103] [Citation(s) in RCA: 364] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2006] [Indexed: 11/18/2022] Open
Abstract
Influenza virus remains a global health threat, with millions of infections annually and the impending threat that a strain of avian influenza may develop into a human pandemic. Despite its importance as a pathogen, little is known about the virus structure, in part because of its intrinsic structural variability (pleiomorphy): the primary distinction is between spherical and elongated particles, but both vary in size. Pleiomorphy has thwarted structural analysis by image reconstruction of electron micrographs based on averaging many identical particles. In this study, we used cryoelectron tomography to visualize the 3D structures of 110 individual virions of the X-31 (H3N2) strain of influenza A. The tomograms distinguish two kinds of glycoprotein spikes [hemagglutinin (HA) and neuraminidase (NA)] in the viral envelope, resolve the matrix protein layer lining the envelope, and depict internal configurations of ribonucleoprotein (RNP) complexes. They also reveal the stems that link the glycoprotein ectodomains to the membrane and interactions among the glycoproteins, the matrix, and the RNPs that presumably control the budding of nascent virions from host cells. Five classes of virions, four spherical and one elongated, are distinguished by features of their matrix layer and RNP organization. Some virions have substantial gaps in their matrix layer ("molecular fontanels"), and others appear to lack a matrix layer entirely, suggesting the existence of an alternative budding pathway in which matrix protein is minimally involved.
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Affiliation(s)
- Audray Harris
- *Laboratory of Structural Biology, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD 20892; and
| | - Giovanni Cardone
- *Laboratory of Structural Biology, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD 20892; and
| | - Dennis C. Winkler
- *Laboratory of Structural Biology, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD 20892; and
| | - J. Bernard Heymann
- *Laboratory of Structural Biology, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD 20892; and
| | - Matthew Brecher
- Department of Microbiology, University of Virginia, Charlottesville, VA 22908
| | - Judith M. White
- Department of Microbiology, University of Virginia, Charlottesville, VA 22908
| | - Alasdair C. Steven
- *Laboratory of Structural Biology, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD 20892; and
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Anwar T, Lal SK, Khan AU. Matrix protein 1: A comparative in silico study on different strains of influenza A H5N1 Virus. Bioinformation 2006; 1:253-6. [PMID: 17597902 PMCID: PMC1891697 DOI: 10.6026/97320630001253] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2006] [Accepted: 11/21/2006] [Indexed: 11/24/2022] Open
Abstract
The importance of influenza viruses as worldwide infectious agents is well
recognized. Specific mutations and evolution in influenza viruses is difficult
to predict. We studied specific mutations in matrix protein 1 (M1) of H5N1
influenza A virus together with properties associated with it using prediction
tools developed in Bioinformatics. Changes in hydrophobicity, polarity and
secondary structure at the site of mutation were noticed and documented to gain
insight towards its infection.
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Affiliation(s)
| | - Sunil K Lal
- International Center for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110 067, India
| | - Asad U Khan
- Distributed Information Sub-centre
- Interdisciplinary Biotechnology Unit Aligarh Muslim University, Aligarh 202002, India
- Asad U Khan
E-mail:
Phone: +91 571 2723088; Fax: +91 571 2721776; Corresponding author
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31
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Perlman S, Holmes KV. Ultrastructure of SARS-CoV, FIPV, and MHV revealed by electron cryomicroscopy. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2006; 581:181-5. [PMID: 17037527 PMCID: PMC7123189 DOI: 10.1007/978-0-387-33012-9_31] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Affiliation(s)
- Stanley Perlman
- Department of Pediatrics, University of Iowa, 52242 Iowa City, IA USA
| | - Kathryn V. Holmes
- Department of Microbiology, University of Colorado Health Sciences Center at Fitzsimons, 80045-8333 Aurora, CO USA
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32
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Neuman BW, Adair BD, Burns JW, Milligan RA, Buchmeier MJ, Yeager M. Complementarity in the supramolecular design of arenaviruses and retroviruses revealed by electron cryomicroscopy and image analysis. J Virol 2005; 79:3822-30. [PMID: 15731275 PMCID: PMC1075687 DOI: 10.1128/jvi.79.6.3822-3830.2005] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Arenaviruses are rodent-borne agents of diseases, including potentially lethal human hemorrhagic fevers. These enveloped viruses encapsidate a bisegmented ambisense single-stranded RNA genome that can be packaged in variable copy number. Electron cryomicroscopy and image analysis of New World Pichinde and Tacaribe arenaviruses and Old World lymphocytic choriomeningitis virus revealed pleomorphic enveloped particles ranging in diameter from approximately 400 to approximately 2,000 A. The surface spikes were spaced approximately 100 A apart and extended approximately 90 A from the maximum phospholipid headgroup density of the outer bilayer leaflet. Distinctive stalk and head regions extended radially approximately 30 and approximately 60 A from the outer bilayer leaflet, respectively. Two interior layers of density apposed to the inner leaflet of the viral lipid bilayer were assigned as protein Z and nucleoprotein (NP) molecules on the basis of their appearance, spacing, and projected volume. Analysis of en face views of virions lacking the GP-C spikes showed reflections consistent with paracrystalline packing of the NP molecules in a lattice with edges of approximately 57 and approximately 74 A. The structural proteins of retroviruses and arenaviruses assemble with similar radial density distributions, using common cellular components.
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Affiliation(s)
- Benjamin W Neuman
- Department of Neuropharmacology, The Scripps Research Institute, 10550 N. Torrey Pines Rd., La Jolla, CA 92037, USA.
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33
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Burleigh LM, Calder LJ, Skehel JJ, Steinhauer DA. Influenza a viruses with mutations in the m1 helix six domain display a wide variety of morphological phenotypes. J Virol 2005; 79:1262-70. [PMID: 15613353 PMCID: PMC538569 DOI: 10.1128/jvi.79.2.1262-1270.2005] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Several functions required for the replication of influenza A viruses have been attributed to the viral matrix protein (M1), and a number of studies have focused on a region of the M1 protein designated "helix six." This region contains an exposed positively charged stretch of amino acids, including the motif 101-RKLKR-105, which has been identified as a nuclear localization signal, but several studies suggest that this domain is also involved in functions such as binding to the ribonucleoprotein genome segments (RNPs), membrane association, interaction with the viral nuclear export protein, and virus assembly. In order to define M1 functions in more detail, a series of mutants containing alanine substitutions in the helix six region were generated in A/WSN/33 virus. These were analyzed for RNP-binding function, their capacity to incorporate into infectious viruses by using reverse genetics, the replication properties of rescued viruses, and the morphological phenotypes of the mutant virus particles. The most notable effect that was identified concerned single amino acid substitution mutants that caused significant alterations to the morphology of budded viruses. Whereas A/WSN/33 virus generally forms particles that are predominantly spherical, observations made by negative stain electron microscopy showed that several of the mutant virions, such as K95A, K98A, R101A, and K102A, display a wide range of shapes and sizes that varied in a temperature-dependent manner. The K102A mutant is particularly interesting in that it can form extended filamentous particles. These results support the proposition that the helix six domain is involved in the process of virus assembly.
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Affiliation(s)
- Laura M Burleigh
- Department of Microbiology and Immunology, Emory University School of Medicine, Rollins Research Center, 1510 Clifton Rd., Atlanta, GA 30322, USA
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34
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Sato Y, Yoshioka K, Suzuki C, Awashima S, Hosaka Y, Yewdell J, Kuroda K. Localization of influenza virus proteins to nuclear dot 10 structures in influenza virus-infected cells. Virology 2003; 310:29-40. [PMID: 12788628 DOI: 10.1016/s0042-6822(03)00104-1] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
We studied influenza virus M1 protein by generating HeLa and MDCK cell lines that express M1 genetically fused to green fluorescent protein (GFP). GFP-M1 was incorporated into virions produced by influenza virus infected MDCK cells expressing the fusion protein indicating that the fusion protein is at least partially functional. Following infection of either HeLa or MDCK cells with influenza A virus (but not influenza B virus), GFP-M1 redistributes from its cytosolic/nuclear location and accumulates in nuclear dots. Immunofluorescence revealed that the nuclear dots represent nuclear dot 10 (ND10) structures. The colocalization of authentic M1, as well as NS1 and NS2 protein, with ND10 was confirmed by immunofluorescence following in situ isolation of ND10. These findings demonstrate a previously unappreciated involvement of influenza virus with ND10, a structure involved in cellular responses to immune cytokines as well as the replication of a rapidly increasing list of viruses.
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Affiliation(s)
- Yoshiko Sato
- Department of Virology and Immunology, Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka 569-1094, Japan
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35
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Subczynski WK, Kusumi A. Dynamics of raft molecules in the cell and artificial membranes: approaches by pulse EPR spin labeling and single molecule optical microscopy. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1610:231-43. [PMID: 12648777 DOI: 10.1016/s0005-2736(03)00021-x] [Citation(s) in RCA: 143] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Lipid rafts in the plasma membrane, domains rich in cholesterol and sphingolipids, have been implicated in a number of important membrane functions. Detergent insolubility has been used to define membrane "rafts" biochemically. However, such an approach does not directly contribute to the understanding of the size and the lifetime of rafts, dynamics of the raft-constituent molecules, and the function of rafts in the membrane in situ. To address these issues, we have developed pulse EPR spin labeling and single molecule tracking optical techniques for studies of rafts in both artificial and cell membranes. In this review, we summarize our results and perspectives obtained by using these methods. We emphasize the importance of clearly distinguishing small/unstable rafts (lifetime shorter than a millisecond) in unstimulated cells and stabilized rafts induced by liganded and oligomerized (GPI-anchored) receptor molecules (core receptor rafts, lifetime over a few minutes). We propose that these stabilized rafts further induce temporal, greater rafts (signaling rafts, lifetime on the order of a second) for signaling by coalescing other small/unstable rafts, including those in the inner leaflet of the membrane, each containing perhaps one molecule of the downstream effector molecules. At variance with the general view, we emphasize the importance of cholesterol segregation from the liquid-crystalline unsaturated bulk-phase membrane for formation of the rafts, rather than the affinity of cholesterol and saturated alkyl chains. In the binary mixture of cholesterol and an unsaturated phospholipid, cholesterol is segregated out from the bulk unsaturated liquid-crystalline phase, forming cholesterol-enriched domains or clustered cholesterol domains, probably due to the lateral nonconformability between the rigid planar transfused ring structure of cholesterol and the rigid bend of the unsaturated alkyl chain at C9-C10. However, such cholesterol-rich domains are small, perhaps consisting of only several cholesterol molecules, and are short-lived, on the order of 1-100 ns. We speculate that these cholesterol-enriched domains may be stabilized by the presence of saturated alkyl chains of sphingomyelin or glycosphingolipids, and also by clustered raft proteins. In the influenza viral membrane, one of the simplest forms of a biological membrane, the lifetime of a protein and cholesterol-rich domain was evaluated to be on the order of 100 micro, again showing the short lifetime of rafts in an unstimulated state. Finally, we propose a thermal Lego model for rafts as the basic building blocks for signaling pathways in the plasma membrane.
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Affiliation(s)
- Witold K Subczynski
- National Biomedical EPR Center, Biophysics Research Institute, The Medical College of Wisconsin, Milwaukee, WI 53226, USA
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36
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Kawasaki K, Yin JJ, Subczynski WK, Hyde JS, Kusumi A. Pulse EPR detection of lipid exchange between protein-rich raft and bulk domains in the membrane: methodology development and its application to studies of influenza viral membrane. Biophys J 2001; 80:738-48. [PMID: 11159441 PMCID: PMC1301272 DOI: 10.1016/s0006-3495(01)76053-5] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
A pulse saturation-recovery electron paramagnetic resonance (EPR) method has been developed that allows estimation of the exchange rates of a spin-labeled lipid between the bulk domain and the protein-rich membrane domain, in which the rate of collision between the spin label and molecular oxygen is reduced (slow-oxygen transport domain, or SLOT domain). It is based on the measurements of saturation-recovery signals of a lipid spin label as a function of concentrations of both molecular oxygen and the spin label. Influenza viral membrane, one of the simplest paradigms for the study of biomembranes, showed the presence of two membrane domains with slow and fast collision rates with oxygen (a 16-fold difference) at 30 degrees C. The outbound rate from and the inbound rate into the SLOT domain (or possibly the rate of the domain disintegration and formation) were estimated to be 7.7 x 10(4) and 4.6 x 10(4) s(-1), (15 micros residency time), respectively, indicating that the SLOT domain is highly dynamic and that the entire SLOT domain represents about one-third of the membrane area. Because the oxygen transport rate in the SLOT domain is a factor of two smaller than that in purple membrane, where bacteriorhodopsin is aggregated, we propose that the SLOT domain in the viral membrane is the cholesterol-rich raft domain stabilized by the trimers of hemagglutinin and/or the tetramers of neuraminidase.
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Affiliation(s)
- K Kawasaki
- National Institute of Bioscience and Human Technology, Tsukuba 305-8566, Japan
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37
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Ruigrok RW, Barge A, Durrer P, Brunner J, Ma K, Whittaker GR. Membrane interaction of influenza virus M1 protein. Virology 2000; 267:289-98. [PMID: 10662624 DOI: 10.1006/viro.1999.0134] [Citation(s) in RCA: 124] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The M1 protein of influenza virus is thought to make contact with the cytoplasmic tails of the glycoprotein spikes, lipid molecules in the viral membrane, and the internal ribonucleoprotein particles. Here we show electron micrographs of negatively stained virus particles in which M1 is visualized as a 60-A-long rod that touches the membrane but apparently is not membrane inserted. Photolabeling with a membrane restricted reagent resulted in labeling of the transmembrane region of haemagglutinin but not of M1, also suggesting that most of M1 is not embedded into the hydrophobic core of the viral membrane. Finally, in vitro reconstitution experiments using soluble M1 protein and synthetic liposomes or Madin-Darby canine kidney cell membranes suggest that M1 can bind to negatively charged liposomes and to the cellular membranes and that this binding can be prevented under high-salt conditions. Although none of these experiments prove that there does not exist a minor fraction of M1 that is membrane inserted, it appears that most of M1 in the virus is membrane associated through electrostatic interactions.
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Affiliation(s)
- R W Ruigrok
- EMBL Grenoble Outstation, Grenoble Cedex 9, 38042, France.
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38
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Korte T, Ludwig K, Booy FP, Blumenthal R, Herrmann A. Conformational intermediates and fusion activity of influenza virus hemagglutinin. J Virol 1999; 73:4567-74. [PMID: 10233915 PMCID: PMC112497 DOI: 10.1128/jvi.73.6.4567-4574.1999] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Three strains of influenza virus (H1, H2, and H3) exhibited similar characteristics in the ability of their hemagglutinin (HA) to induce membrane fusion, but the HAs differed in their susceptibility to inactivation. The extent of inactivation depended on the pH of preincubation and was lowest for A/Japan (H2 subtype), in agreement with previous studies (A. Puri, F. Booy, R. W. Doms, J. M. White, and R. Blumenthal, J. Virol. 64:3824-3832, 1990). While significant inactivation of X31 (H3 subtype) was observed at 37 degrees C at pH values corresponding to the maximum of fusion (about pH 5.0), no inactivation was seen at preincubation pH values 0.2 to 0.4 pH units higher. Surprisingly, low-pH preincubation under those conditions enhanced the fusion rates and extents of A/Japan as well as those of X31. For A/PR 8/34 (H1 subtype), neither a shift of the pH (to >5.0) nor a decrease of the temperature to 20 degrees C was sufficient to prevent inactivation. We provide evidence that the activated HA is a conformational intermediate distinct from the native structure and from the final structure associated with the conformational change of HA, which is implicated by the high-resolution structure of the soluble trimeric fragment TBHA2 (P. A. Bullough, F. M. Hughson, J. J. Skehel, and D. C. Wiley, Nature 371:37-43, 1994).
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Affiliation(s)
- T Korte
- Laboratory of Experimental and Computational Biology, National Cancer Institute-Frederick Cancer Research & Development Center, National Institutes of Health, Frederick, Maryland 21702, USA
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39
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Shangguan T, Siegel DP, Lear JD, Axelsen PH, Alford D, Bentz J. Morphological changes and fusogenic activity of influenza virus hemagglutinin. Biophys J 1998; 74:54-62. [PMID: 9449309 PMCID: PMC1299361 DOI: 10.1016/s0006-3495(98)77766-5] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The kinetics of low-pH induced fusion of influenza virus with liposomes have been compared to changes in the morphology of influenza hemagglutinin (HA). At pH 4.9 and 30 degrees C, the fusion of influenza A/PR/8/34 virus with ganglioside-bearing liposomes was complete within 6 min. Virus preincubated at pH 4.9 and 30 degrees C in the absence of liposomes for 2 or 10 min retained most of its fusion activity. However, fusion activity was dramatically reduced after 30 min, and virtually abolished after a 60-min preincubation. Cryo-electron microscopy showed that the hemagglutinin spikes of virions exposed to pH 4.9 at 30 degrees C for 10 min underwent no major morphological changes. After 30 min, however, the spike morphology changed dramatically, and further changes occurred for up to 60 min after exposure to low pH. Because the morphological changes occur at a rate corresponding to the loss of fusion activity, and because these changes are much slower than the rate at which fusion occurs, we conclude that the morphologically altered HA is inactive with respect to fusion-promoting activity. Molecular modeling studies indicate that the formation of an extended coiled coil within the HA trimer, as proposed for HA at low pH, requires a major conformational change in HA, and that the morphological changes we observe are consistent with the formation of an extended coiled coil. These results imply that the crystallographically determined low-pH form of HA does occur in the intact virus, but that this form is not a precursor of viral fusion. It is speculated that the motion to the low-pH form may be responsible for the membrane destabilization leading to fusion.
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Affiliation(s)
- T Shangguan
- Department of Bioscience and Biotechnology, Drexel University, Philadelphia, Pennsylvania 19104, USA
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40
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Cerritelli ME, Cheng N, Rosenberg AH, McPherson CE, Booy FP, Steven AC. Encapsidated conformation of bacteriophage T7 DNA. Cell 1997; 91:271-80. [PMID: 9346244 DOI: 10.1016/s0092-8674(00)80409-2] [Citation(s) in RCA: 252] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The structural organization of encapsidated T7 DNA was investigated by cryo-electron microscopy and image processing. A tail-deletion mutant was found to present two preferred views of phage heads: views along the axis through the capsid vertex where the connector protein resides and via which DNA is packaged; and side views perpendicular to this axis. The resulting images reveal striking patterns of concentric rings in axial views, and punctate arrays in side views. As corroborated by computer modeling, these data establish that the T7 chromosome is spooled around this axis in approximately six coaxial shells in a quasi-crystalline packing, possibly guided by the core complex on the inner surface of the connector.
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Affiliation(s)
- M E Cerritelli
- Laboratory of Structural Biology, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
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41
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Bar-Zvi D, Yoshida M, Shavit N. Modification of domains of alpha and beta subunits of F1-ATPase from the thermophylic bacterium PS3, in their isolated and associated forms, by 3'-O-(4-benzoyl)benzoyl adenosine 5'-triphosphate (BzATP). J Bioenerg Biomembr 1996; 28:471-81. [PMID: 8953379 DOI: 10.1007/bf02110437] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Photoaffinity labeling by 3'-O-(4-benzoyl)benzoyl adenosine 5'-triphosphate (BzATP) of the adenine nucleotide binding site(s) on isolated and complexed alpha and beta subunits of F1-ATPase from the thermophilic bacterium PS3 (TF1) is described. BzATP binds to both isolated alpha and beta subunits, to complexed beta subunit but not to complexed alpha subunit. Amino acid sequence determination of radiolabeled peptides obtained by proteolytic digestion of [gamma-32P]BzATP-labeled alpha subunit indicates that residues on both the amino-terminal (residues A41-E67) and carboxy-terminal (residues Q422-Q476) were modified by BzATP. One of the residues in the carboxy-terminal modified by BzATP is most probably alpha Q422. Although the binding stoichiometry of 1 mol of BzATP incorporated by either isolated or complexed beta subunit was maintained, the spatial conformation of the polypeptide determines which amino acid residue(s) is more accessible to the reactive radical. CNBr derived fragments beta G10-M64, beta E75-M233, and beta D390-M469 were labeled with the isolated beta subunit. With complexed beta subunit the label was found only in CNBr fragments: beta E75-M233 and beta G339-M389. The locations where the covalently bound BzATP was found, in the soluble and assembled subunits, indicate that different conformational states exist. In the isolated form of the alpha and beta subunits the amino- and carboxy-termini can fold and reach the central domain of the polypeptide, the domain containing the adenine nucleotide binding site. When alpha combines with beta to form the alpha 3 beta 3 core complex the new conformation of the subunits is such that covalent labeling by BzATP of alpha and of the amino terminal of beta subunit is excluded.
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Affiliation(s)
- D Bar-Zvi
- Doris and Bertie Black Center of Bioenergetics in Life Sciences, Ben Gurion University of the Negev, Beer Sheva, Israel
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42
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Nermut MV, Grief C, Hashmi S, Hockley DJ. Further evidence of icosahedral symmetry in human and simian immunodeficiency virus. AIDS Res Hum Retroviruses 1993; 9:929-38. [PMID: 8280478 DOI: 10.1089/aid.1993.9.929] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Specimens of HIV and SIV have been examined by electron microscopy, using the techniques of conventional thin sectioning, freeze-substitution, cryosectioning, and cryomicroscopy of frozen hydrated specimens. In addition freeze-drying and critical point drying were used for both shadowed replicas and scanning electron microscopy. Thin sections revealed hexagonal, pentagonal, or near-spherical profiles. Angular particles were seen in shadowed replicas and also by scanning electron microscopy. The images observed were consistent with an icosahedral shape of the virus. It is proposed that mature HIV (SIV) is an icosadeltahedron with flat triangular facets. Size measurements of the specimens showed a wide range of values for conventional embedding, but a narrow range for specimens prepared by low-temperature techniques.
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Affiliation(s)
- M V Nermut
- National Institute for Biological Standards and Control, Hertfordshire, England
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43
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Burger KN, Calder LJ, Frederik PM, Verkleij AJ. Electron microscopy of virus--liposome fusion. Methods Enzymol 1993; 220:362-79. [PMID: 8350762 DOI: 10.1016/0076-6879(93)20095-k] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- K N Burger
- Department of Cell Biology, Medical School AZU, University of Utrecht, The Netherlands
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44
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Guy HR, Durell SR, Schoch C, Blumenthal R. Analyzing the fusion process of influenza hemagglutinin by mutagenesis and molecular modeling. Biophys J 1992; 62:95-7. [PMID: 1600107 PMCID: PMC1260496 DOI: 10.1016/s0006-3495(92)81790-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Affiliation(s)
- H R Guy
- Lab of Mathematical Biology, DCBDC, NCI, National Institutes of Health, Bethesda, Maryland 20892
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45
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Lünsdorf H, Tiedge H. Immunoelectron microscopy of enzymes, multienzyme complexes, and selected other oligomeric proteins. ELECTRON MICROSCOPY REVIEWS 1992; 5:105-27. [PMID: 1730073 DOI: 10.1016/0892-0354(92)90007-d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The collective term "immunoelectron microscopy" subsumes a number of techniques in which the biological material is decorated with specific antibodies, prior to being visualized in the electron microscope. In this article, we have reviewed literature on immunoelectron microscopy that focusses on the analysis of the molecular architecture of proteins, in particular of enzymes and of multienzyme complexes. Molecular immunoelectron microscopy has been remarkably successful with multi-subunit enzymes of complex quaternary structures, and in many cases the data have been the basis for the eventual development of detailed three-dimensional molecular models. The elucidation of subunit composition and juxtaposition of a given enzyme, an important accomplishment in itself, has in turn stimulated and guided discussions on the catalytic mechanism; illustrative examples include F1 ATPase and citrate lyase, among others. Here we have chosen a variety of enzymes, multienzyme complexes, and non-enzymatic proteins to demonstrate the versatility of immunoelectron microscopy, to illustrate methodological prerequisites and limitations, and to discuss significance and implications of individual immunoelectron microscopy studies.
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Affiliation(s)
- H Lünsdorf
- Bereich Mikrobiologie, Gesellschaft für Biotechnologische Forschung, Braunschweig, Germany
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46
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Murti KG, Brown PS, Bean WJ, Webster RG. Composition of the helical internal components of influenza virus as revealed by immunogold labeling/electron microscopy. Virology 1992; 186:294-9. [PMID: 1727605 DOI: 10.1016/0042-6822(92)90084-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The composition of the large helical internal components of influenza virus was investigated by immunogold labeling/electron microscopy with antibodies to the nucleoprotein (NP), matrix protein (M), and polymerase complex (PB1, PB2, and PA) of the virus. The morphologically intact helices, obtained by air-drying of the virions on the electron microscope grid, showed little or no labeling with any of the above antibodies. However, partial to full degradation of the helix by proteinase K (2 ng/ml) prior to immunogold labeling made the helices accessible to all three antibodies. The results are consistent with a model that the helix represents a polymer of M protein enclosing or containing the influenza ribonucleoprotein(s).
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Affiliation(s)
- K G Murti
- Department of Virology and Molecular Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38101-0318
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47
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Blumenthal R, Schoch C, Puri A, Clague MJ. A dissection of steps leading to viral envelope protein-mediated membrane fusion. Ann N Y Acad Sci 1991; 635:285-96. [PMID: 1741588 DOI: 10.1111/j.1749-6632.1991.tb36499.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- R Blumenthal
- Section on Membrane Structure and Function, National Cancer Institute, National Insitutes of Health, Bethesda, Maryland 20892
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48
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Booy FP, Newcomb WW, Trus BL, Brown JC, Baker TS, Steven AC. Liquid-crystalline, phage-like packing of encapsidated DNA in herpes simplex virus. Cell 1991; 64:1007-15. [PMID: 1848156 PMCID: PMC4140082 DOI: 10.1016/0092-8674(91)90324-r] [Citation(s) in RCA: 199] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The organization of DNA within the HSV-1 capsid has been determined by cryoelectron microscopy and image reconstruction. Purified C-capsids, which are fully packaged, were compared with A-capsids, which are empty. Unlike A-capsids, C-capsids show fine striations and punctate arrays with a spacing of approximately 2.6 nm. The packaged DNA forms a uniformly dense ball, extending radially as far as the inner surface of the icosahedral (T = 16) capsid shell, whose structure is essentially identical in A-capsids and C-capsids. Thus we find no evidence for the inner T = 4 shell previously reported by Schrag et al. to be present in C-capsids. Encapsidated HSV-1 DNA closely resembles that previously visualized in bacteriophages T4 and lambda, thus supporting the idea of a close parallelism between the respective assembly pathways of a major family of animal viruses (the herpesviruses) and a major family of bacterial viruses.
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Affiliation(s)
- F P Booy
- Laboratory of Structural Biology Research, National Institute of Arthritis, Musculoskeletal and Skin Diseases, NIH, Bethesda, Maryland 20892
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Ruigrok RW, Hewat EA. Comparison of negatively stained and frozen hydrated samples of influenza viruses A and B and of vesicular stomatitis virus. ACTA ACUST UNITED AC 1991. [DOI: 10.1016/0739-6260(91)90060-d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Puri A, Booy FP, Doms RW, White JM, Blumenthal R. Conformational changes and fusion activity of influenza virus hemagglutinin of the H2 and H3 subtypes: effects of acid pretreatment. J Virol 1990; 64:3824-32. [PMID: 2196382 PMCID: PMC249678 DOI: 10.1128/jvi.64.8.3824-3832.1990] [Citation(s) in RCA: 122] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Marked differences were observed between the H2 and H3 strains of influenza virus in their sensitivity to pretreatment at low pH. Whereas viral fusion and hemolysis mediated by influenza virus X:31 (H3 subtype) were inactivated by pretreatment of the virus at low pH, influenza virus A/Japan/305/57 (H2 subtype) retained those activities even after a 15-min incubation at pH 5.0 and 37 degrees C. Fusion with erythrocytes was measured by using the octadecylrhodamine-dequenching assay with both intact virions and CV-1 monkey kidney cells expressing hemagglutinin (HA) on the plasma membrane. To study the nature of the differences between the two strains, we examined the effects of low-pH treatment on the conformational change of HA by its susceptibility to protease digestion, exposure of the fusion peptide, and electron microscopy of unstained, frozen, hydrated virus. We found that the respective HA molecules from the two strains assumed different conformational states after exposure to low pH. The relationship between the conformation of HA and its fusogenic activity is discussed in the context of these experiments.
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Affiliation(s)
- A Puri
- Section on Membrane Structure and Function, National Cancer Institute, Bethesda, Maryland 20892
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