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Goetschius DJ, Hartmann SR, Organtini LJ, Callaway H, Huang K, Bator CM, Ashley RE, Makhov AM, Conway JF, Parrish CR, Hafenstein SL. High-resolution asymmetric structure of a Fab-virus complex reveals overlap with the receptor binding site. Proc Natl Acad Sci U S A 2021; 118:e2025452118. [PMID: 34074770 PMCID: PMC8201801 DOI: 10.1073/pnas.2025452118] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Canine parvovirus is an important pathogen causing severe diseases in dogs, including acute hemorrhagic enteritis, myocarditis, and cerebellar disease. Overlap on the surface of parvovirus capsids between the antigenic epitope and the receptor binding site has contributed to cross-species transmission, giving rise to closely related variants. It has been shown that Mab 14 strongly binds and neutralizes canine but not feline parvovirus, suggesting this antigenic site also controls species-specific receptor binding. To visualize the conformational epitope at high resolution, we solved the cryogenic electron microscopy (cryo-EM) structure of the Fab-virus complex. We also created custom software, Icosahedral Subparticle Extraction and Correlated Classification, to solve a Fab-virus complex with only a few Fab bound per capsid and visualize local structures of the Fab-bound and -unbound antigenic sites extracted from the same complex map. Our results identified the antigenic epitope that had significant overlap with the receptor binding site, and the structures revealed that binding of Fab induced conformational changes to the virus. We were also able to assign the order and position of attached Fabs to allow assessment of complementarity between the Fabs bound to different positions. This approach therefore provides a method for using cryo-EM to investigate complementarity of antibody binding.
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Affiliation(s)
- Daniel J Goetschius
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802
| | - Samantha R Hartmann
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802
| | - Lindsey J Organtini
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802
| | - Heather Callaway
- Baker Institute for Animal Health, Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853
| | - Kai Huang
- Baker Institute for Animal Health, Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853
| | - Carol M Bator
- Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA 16802
| | - Robert E Ashley
- Department of Medicine, Penn State University College of Medicine, The Pennsylvania State University, Hershey, PA 17033
| | - Alexander M Makhov
- Department of Structural Biology, University of Pittsburgh School of Medicine, University of Pittsburgh, Pittsburgh, PA 15260
| | - James F Conway
- Department of Structural Biology, University of Pittsburgh School of Medicine, University of Pittsburgh, Pittsburgh, PA 15260
| | - Colin R Parrish
- Baker Institute for Animal Health, Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853
| | - Susan L Hafenstein
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802;
- Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA 16802
- Department of Medicine, Penn State University College of Medicine, The Pennsylvania State University, Hershey, PA 17033
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Guan J, Bywaters SM, Brendle SA, Ashley RE, Makhov AM, Conway JF, Christensen ND, Hafenstein S. High-Resolution Structure Analysis of Antibody V5 and U4 Conformational Epitopes on Human Papillomavirus 16. Viruses 2017; 9:v9120374. [PMID: 29211035 PMCID: PMC5744149 DOI: 10.3390/v9120374] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Revised: 11/13/2017] [Accepted: 11/18/2017] [Indexed: 01/14/2023] Open
Abstract
Cancers attributable to human papillomavirus (HPV) place a huge burden on the health of both men and women. The current commercial vaccines are genotype specific and provide little therapeutic benefit to patients with existing HPV infections. Identifying the conformational epitopes on the virus capsid supports the development of improved recombinant vaccines to maximize long-term protection against multiple types of HPV. Fragments of antibody (Fab) digested from the neutralizing monoclonal antibodies H16.V5 (V5) and H16.U4 (U4) were bound to HPV16 capsids and the structures of the two virus-Fab complexes were solved to near atomic resolution using cryo-electron microscopy. The structures reveal virus conformational changes, the Fab-binding mode to the capsid, the residues comprising the epitope and indicate a potential interaction of U4 with the minor structural protein, L2. Competition enzyme-linked immunosorbent assay (ELISA) showed V5 outcompetes U4 when added sequentially, demonstrating a steric interference even though the footprints do not overlap. Combined with our previously reported immunological and structural results, we propose that the virus may initiate host entry through an interaction between the icosahedral five-fold vertex of the capsid and receptors on the host cell. The highly detailed epitopes identified for the two antibodies provide a framework for continuing biochemical, genetic and biophysical studies.
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Affiliation(s)
- Jian Guan
- Department of Medicine, The Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033, USA.
| | - Stephanie M Bywaters
- Department of Pathology, The Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033, USA.
| | - Sarah A Brendle
- Department of Pathology, The Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033, USA.
| | - Robert E Ashley
- Department of Medicine, The Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033, USA.
| | - Alexander M Makhov
- Department of Structural Biology, University of Pittsburgh School of Medicine, 3501 5th Ave, Pittsburgh, PA 15260, USA.
| | - James F Conway
- Department of Structural Biology, University of Pittsburgh School of Medicine, 3501 5th Ave, Pittsburgh, PA 15260, USA.
| | - Neil D Christensen
- Department of Pathology, The Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033, USA.
| | - Susan Hafenstein
- Department of Medicine, The Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033, USA.
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, Millennium Science Complex, University Park, State College, PA 16802, USA.
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Guan J, Bywaters SM, Brendle SA, Ashley RE, Makhov AM, Conway JF, Christensen ND, Hafenstein S. Cryoelectron Microscopy Maps of Human Papillomavirus 16 Reveal L2 Densities and Heparin Binding Site. Structure 2017; 25:253-263. [PMID: 28065506 DOI: 10.1016/j.str.2016.12.001] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Revised: 10/07/2016] [Accepted: 12/12/2016] [Indexed: 11/24/2022]
Abstract
Human papillomavirus (HPV) is a significant health burden and leading cause of virus-induced cancers. The current commercial vaccines are genotype specific and provide little therapeutic benefit to patients with existing HPV infections. Host entry mechanisms represent an excellent target for alternative therapeutics, but HPV receptor use, the details of cell attachment, and host entry are inadequately understood. Here we present near-atomic resolution structures of the HPV16 capsid and HPV16 in complex with heparin, both determined from cryoelectron micrographs collected with direct electron detection technology. The structures clarify details of capsid architecture for the first time, including variation in L1 major capsid protein conformation and putative location of L2 minor protein. Heparin binds specifically around the capsid icosahedral vertices and may recapitulate the earliest stage of infection, providing a framework for continuing biochemical, genetic, and biophysical studies.
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Affiliation(s)
- Jian Guan
- Division of Infectious Diseases, Department of Medicine, Penn State College of Medicine, The Pennsylvania State University College of Medicine, Mail Code H036, 500 University Drive, P.O. Box 850, Hershey, PA 17033-0850, USA
| | - Stephanie M Bywaters
- Department of Pathology, The Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033, USA
| | - Sarah A Brendle
- Department of Pathology, The Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033, USA
| | - Robert E Ashley
- Division of Infectious Diseases, Department of Medicine, Penn State College of Medicine, The Pennsylvania State University College of Medicine, Mail Code H036, 500 University Drive, P.O. Box 850, Hershey, PA 17033-0850, USA
| | - Alexander M Makhov
- Department of Structural Biology, University of Pittsburgh School of Medicine, 3501 5th Avenue, Pittsburgh, PA 15260, USA
| | - James F Conway
- Department of Structural Biology, University of Pittsburgh School of Medicine, 3501 5th Avenue, Pittsburgh, PA 15260, USA
| | - Neil D Christensen
- Department of Pathology, The Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033, USA
| | - Susan Hafenstein
- Division of Infectious Diseases, Department of Medicine, Penn State College of Medicine, The Pennsylvania State University College of Medicine, Mail Code H036, 500 University Drive, P.O. Box 850, Hershey, PA 17033-0850, USA.
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Lee H, Shingler KL, Organtini LJ, Ashley RE, Makhov AM, Conway JF, Hafenstein S. The novel asymmetric entry intermediate of a picornavirus captured with nanodiscs. Sci Adv 2016; 2:e1501929. [PMID: 27574701 PMCID: PMC4996645 DOI: 10.1126/sciadv.1501929] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Accepted: 07/28/2016] [Indexed: 06/06/2023]
Abstract
Many nonenveloped viruses engage host receptors that initiate capsid conformational changes necessary for genome release. Structural studies on the mechanisms of picornavirus entry have relied on in vitro approaches of virus incubated at high temperatures or with excess receptor molecules to trigger the entry intermediate or A-particle. We have induced the coxsackievirus B3 entry intermediate by triggering the virus with full-length receptors embedded in lipid bilayer nanodiscs. These asymmetrically formed A-particles were reconstructed using cryo-electron microscopy and a direct electron detector. These first high-resolution structures of a picornavirus entry intermediate captured at a membrane with and without imposing icosahedral symmetry (3.9 and 7.8 Å, respectively) revealed a novel A-particle that is markedly different from the classical A-particles. The asymmetric receptor binding triggers minimal global capsid expansion but marked local conformational changes at the site of receptor interaction. In addition, viral proteins extrude from the capsid only at the site of extensive protein remodeling adjacent to the nanodisc. Thus, the binding of the receptor triggers formation of a unique site in preparation for genome release.
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Affiliation(s)
- Hyunwook Lee
- The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
| | - Kristin L. Shingler
- The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
| | | | - Robert E. Ashley
- The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
| | | | - James F. Conway
- University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, USA
| | - Susan Hafenstein
- The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
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5
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Abstract
Due to the inherent limitations of conventional antibiotics for the treatment of C. difficile infection (CDI), there is a growing interest in the development of alternative treatment strategies. Both bacteriophages and R-type bacteriocins, also known as phage tail-like particles (PTLPs), show promise as potential antibacterial alternatives for treating CDI. Similar to bacteriophages, but lacking a viral capsid and genome, PTLPs remain capable of killing target bacteria. Here we describe our experience in the induction and purification of C. difficile PTLPs. These methods have been optimized to allow production of concentrated, non-contractile, and non-aggregated samples for both sensitivity testing and structural electron microscopy studies.
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Affiliation(s)
- John P Hegarty
- Department of Surgery, Division of Colorectal Surgery, The Pennsylvania State University College of Medicine, 500 University Drive, H-137, 850, Hershey, PA, 17033, USA.
| | - William Sangster
- Department of Surgery, Division of Colorectal Surgery, The Pennsylvania State University College of Medicine, 500 University Drive, H-137, 850, Hershey, PA, 17033, USA
| | - Robert E Ashley
- Department of Medicine, The Pennsylvania State University College of Medicine, Hershey, PA, USA
- Department of Microbiology & Immunology, The Pennsylvania State University College of Medicine, Hershey, PA, USA
| | - Roland Myers
- Department of Neural and Behavioral Sciences, The Pennsylvania State University College of Medicine, Hershey, PA, USA
| | - Susan Hafenstein
- Department of Medicine, The Pennsylvania State University College of Medicine, Hershey, PA, USA
- Department of Microbiology & Immunology, The Pennsylvania State University College of Medicine, Hershey, PA, USA
| | - David B Stewart
- Department of Surgery, Division of Colorectal Surgery, The Pennsylvania State University College of Medicine, 500 University Drive, H-137, 850, Hershey, PA, 17033, USA.
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Guan J, Bywaters SM, Brendle SA, Lee H, Ashley RE, Makhov AM, Conway JF, Christensen ND, Hafenstein S. Structural comparison of four different antibodies interacting with human papillomavirus 16 and mechanisms of neutralization. Virology 2015; 483:253-63. [PMID: 25996608 DOI: 10.1016/j.virol.2015.04.016] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2015] [Revised: 04/13/2015] [Accepted: 04/17/2015] [Indexed: 01/29/2023]
Abstract
Cryo-electron microscopy (cryo-EM) was used to solve the structures of human papillomavirus type 16 (HPV16) complexed with fragments of antibody (Fab) from three different neutralizing monoclonals (mAbs): H16.1A, H16.14J, and H263.A2. The structure-function analysis revealed predominantly monovalent binding of each Fab with capsid interactions that involved multiple loops from symmetry related copies of the major capsid protein. The residues identified in each Fab-virus interface map to a conformational groove on the surface of the capsomer. In addition to the known involvement of the FG and HI loops, the DE loop was also found to constitute the core of each epitope. Surprisingly, the epitope mapping also identified minor contributions by EF and BC loops. Complementary immunological assays included mAb and Fab neutralization. The specific binding characteristics of mAbs correlated with different neutralizing behaviors in pre- and post-attachment neutralization assays.
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Affiliation(s)
- Jian Guan
- Department of Medicine, The Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033 USA
| | - Stephanie M Bywaters
- Department of Pathology, The Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033 USA
| | - Sarah A Brendle
- Department of Pathology, The Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033 USA
| | - Hyunwook Lee
- Department of Medicine, The Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033 USA
| | - Robert E Ashley
- Department of Medicine, The Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033 USA
| | - Alexander M Makhov
- Department of Structural Biology, University of Pittsburgh School of Medicine, 3501 5th Ave, Pittsburgh, PA 15260 USA
| | - James F Conway
- Department of Structural Biology, University of Pittsburgh School of Medicine, 3501 5th Ave, Pittsburgh, PA 15260 USA
| | - Neil D Christensen
- Department of Pathology, The Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033 USA
| | - Susan Hafenstein
- Department of Medicine, The Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033 USA.
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Gullberg M, Muszynski B, Organtini LJ, Ashley RE, Hafenstein SL, Belsham GJ, Polacek C. Assembly and characterization of foot-and-mouth disease virus empty capsid particles expressed within mammalian cells. J Gen Virol 2013; 94:1769-1779. [PMID: 23740480 DOI: 10.1099/vir.0.054122-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2023] Open
Abstract
The foot-and-mouth disease virus (FMDV) structural protein precursor, P1-2A, is cleaved by the virus-encoded 3C protease (3C(pro)) into the capsid proteins VP0, VP1 and VP3 (and 2A). In some systems, it is difficult to produce large amounts of these processed capsid proteins since 3C(pro) can be toxic for cells. The expression level of 3C(pro) activity has now been reduced relative to the P1-2A, and the effect on the yield of processed capsid proteins and their assembly into empty capsid particles within mammalian cells has been determined. Using a vaccinia-virus-based transient expression system, P1-2A (from serotypes O and A) and 3C(pro) were expressed from monocistronic cDNA cassettes as P1-2A-3C, or from dicistronic cassettes with the 3C(pro) expression dependent on a mutant FMDV internal ribosome entry site (IRES) (designated P1-2A-mIRES-3C). The effects of using a mutant 3C(pro) with reduced catalytic activity or using two different mutant IRES elements (the wt GNRA tetraloop sequence GCGA converted, in the cDNA, to GAGA or GTTA) were analysed. For both serotypes, the P1-2A-mIRES-3C construct containing the inefficient GTTA mutant IRES produced the highest amount of processed capsid proteins. These products self-assembled to form FMDV empty capsid particles, which have a related, but distinct, morphology (as determined by electron microscopy and reconstruction) from that determined previously by X-ray crystallography. The assembled empty capsids bind, in a divalent cation-dependent manner, to the RGD-dependent integrin αvβ6, a cellular receptor for FMDV, and are recognized appropriately in serotype-specific antigen ELISAs.
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Affiliation(s)
- Maria Gullberg
- National Veterinary Institute, Technical University of Denmark, Lindholm, 4771 Kalvehave, Denmark
| | - Bartosz Muszynski
- National Veterinary Institute, Technical University of Denmark, Lindholm, 4771 Kalvehave, Denmark
| | - Lindsey J Organtini
- Department of Microbiology and Immunology, the Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033, USA
| | - Robert E Ashley
- Department of Microbiology and Immunology, the Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033, USA
| | - Susan L Hafenstein
- Department of Microbiology and Immunology, the Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033, USA
| | - Graham J Belsham
- National Veterinary Institute, Technical University of Denmark, Lindholm, 4771 Kalvehave, Denmark
| | - Charlotta Polacek
- National Veterinary Institute, Technical University of Denmark, Lindholm, 4771 Kalvehave, Denmark
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Shingler KL, Yoder JL, Carnegie MS, Ashley RE, Makhov AM, Conway JF, Hafenstein S. The enterovirus 71 A-particle forms a gateway to allow genome release: a cryoEM study of picornavirus uncoating. PLoS Pathog 2013; 9:e1003240. [PMID: 23555253 PMCID: PMC3605244 DOI: 10.1371/journal.ppat.1003240] [Citation(s) in RCA: 92] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2012] [Accepted: 01/28/2013] [Indexed: 12/30/2022] Open
Abstract
Since its discovery in 1969, enterovirus 71 (EV71) has emerged as a serious worldwide health threat. This human pathogen of the picornavirus family causes hand, foot, and mouth disease, and also has the capacity to invade the central nervous system to cause severe disease and death. Upon binding to a host receptor on the cell surface, the virus begins a two-step uncoating process, first forming an expanded, altered “A-particle”, which is primed for genome release. In a second step after endocytosis, an unknown trigger leads to RNA expulsion, generating an intact, empty capsid. Cryo-electron microscopy reconstructions of these two capsid states provide insight into the mechanics of genome release. The EV71 A-particle capsid interacts with the genome near the icosahedral two-fold axis of symmetry, which opens to the external environment via a channel ∼10 Å in diameter that is lined with patches of negatively charged residues. After the EV71 genome has been released, the two-fold channel shrinks, though the overall capsid dimensions are conserved. These structural characteristics identify the two-fold channel as the site where a gateway forms and regulates the process of genome release. In a picornavirus capsid structural integrity must not be compromised until a key mechanism triggers genome release into a permissive cell. It has long been established that the majority of members of the picornavirus family solve this dilemma with a two-step uncoating process initiated by receptor recognition. For human enteroviruses, binding of an entry receptor triggers a series of conformational changes, resulting in an “A-particle” that is primed for genome release. After endocytosis, an unknown trigger causes the A-particle to expel the viral genome, leaving behind an emptied capsid. This process can be mimicked in solution by heating mature virus. Though the capsid species for both of these steps have been isolated, the fine details of the uncoating process have yet to be elucidated. Cryo-electron microscopy reconstructions of the enterovirus 71 A-particle and empty capsid provide compelling structural evidence to suggest that the icosahedral two-fold axis opens a channel that acts as a gateway in the viral capsid, regulating the release of genomic material from the altered particle.
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Affiliation(s)
- Kristin L. Shingler
- Department of Medicine, Department of Microbiology and Immunology, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania, United States of America
| | - Jennifer L. Yoder
- Department of Medicine, Department of Microbiology and Immunology, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania, United States of America
| | - Michael S. Carnegie
- Department of Medicine, Department of Microbiology and Immunology, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania, United States of America
| | - Robert E. Ashley
- Department of Medicine, Department of Microbiology and Immunology, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania, United States of America
| | - Alexander M. Makhov
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - James F. Conway
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Susan Hafenstein
- Department of Medicine, Department of Microbiology and Immunology, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania, United States of America
- * E-mail:
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Cherwa JE, Organtini LJ, Ashley RE, Hafenstein SL, Fane BA. In VITRO ASSEMBLY of the øX174 procapsid from external scaffolding protein oligomers and early pentameric assembly intermediates. J Mol Biol 2011; 412:387-96. [PMID: 21840317 DOI: 10.1016/j.jmb.2011.07.070] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2011] [Revised: 07/29/2011] [Accepted: 07/31/2011] [Indexed: 11/28/2022]
Abstract
Bacteriophage øX174 morphogenesis requires two scaffolding proteins: an internal species, similar to those employed in other viral systems, and an external species, which is more typically associated with satellite viruses. The current model of øX174 assembly is based on structural and in vivo data. During morphogenesis, 240 copies of the external scaffolding protein mediate the association of 12 pentameric particles into procapsids. The hypothesized pentameric intermediate, the 12S⁎ particle, contains 16 proteins: 5 copies each of the coat, spike and internal scaffolding proteins and 1 copy of the DNA pilot protein. Assembly naïve 12S⁎ particles and external scaffolding oligomers, most likely tetramers, formed procapsid-like particles in vitro, suggesting that the 12S⁎ particle is a bona fide assembly intermediate and validating the current model of procapsid morphogenesis. The in vitro system required a crowding agent, was influenced by the ratio of the reactants and was most likely driven by hydrophobic forces. While the system reported here shared some characteristics with other in vitro internal scaffolding protein-mediated systems, it displayed unique features. These features most likely reflect external scaffolding protein-mediated morphogenesis and the øX174 procapsid structure, in which external scaffolding-scaffolding protein interactions, as opposed to coat-coat protein interactions between pentamers, constitute the primary lattice-forming contacts.
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Affiliation(s)
- James E Cherwa
- School of Plant Sciences, University of Arizona, Tucson, AZ 85721, USA
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Ashley RE, Rawlins AG. TAMPON TREATMENT OF SINUS DISEASE IN CHILDREN. Cal West Med 1928; 29:408-409. [PMID: 18740894 PMCID: PMC1656111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
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