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Tomé-Poderti L, Olivero-Deibe N, Carrión F, Portela MM, Obal G, Cabrera G, Bianchi S, Lima A, Addiego A, Durán R, Moratorio G, Pritsch O. Characterization and application of recombinant Bovine Leukemia Virus Env protein. Sci Rep 2024; 14:12190. [PMID: 38806566 PMCID: PMC11133380 DOI: 10.1038/s41598-024-62811-8] [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: 02/20/2024] [Accepted: 05/21/2024] [Indexed: 05/30/2024] Open
Abstract
The Bovine Leukemia Virus (BLV) Envelope (Env) glycoprotein complex is instrumental in viral infectivity and shapes the host's immune response. This study presents the production and characterization of a soluble furin-mutated BLV Env ectodomain (sBLV-EnvFm) expressed in a stable S2 insect cell line. We purified a 63 kDa soluble protein, corresponding to the monomeric sBLV-EnvFm, which predominantly presented oligomannose and paucimannose N-glycans, with a high content of core fucose structures. Our results demonstrate that our recombinant protein can be recognized from specific antibodies in BLV infected cattle, suggesting its potential as a powerful diagnostic tool. Moreover, the robust humoral immune response it elicited in mice shows its potential contribution to the development of subunit-based vaccines against BLV.
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Affiliation(s)
- Lorena Tomé-Poderti
- Immunovirology Lab, Institut Pasteur de Montevideo, 11400, Montevideo, Uruguay.
- Morphogenesis and Antigenicity of HIV and Hepatitis Viruses (MAVIVH), INSERM Unit 1259, Université de Tours and CHRU de Tours, Tours, France.
| | | | - Federico Carrión
- Immunovirology Lab, Institut Pasteur de Montevideo, 11400, Montevideo, Uruguay
| | - María Magdalena Portela
- Analytical Biochemistry and Proteomics Unit, Instituto de Investigaciones Biológicas Clemente Estable/Institut Pasteur de Montevideo, 11400, Montevideo, Uruguay
- Facultad de Ciencias, Universidad de la República, 11400, Montevideo, Uruguay
| | - Gonzalo Obal
- Immunovirology Lab, Institut Pasteur de Montevideo, 11400, Montevideo, Uruguay
| | - Gleysin Cabrera
- Analytical Biochemistry and Proteomics Unit, Instituto de Investigaciones Biológicas Clemente Estable/Institut Pasteur de Montevideo, 11400, Montevideo, Uruguay
| | - Sergio Bianchi
- Laboratory of Molecular Biomarkers, Department of Physiopathology, University Hospital, Universidad de la República, 11600, Montevideo, Uruguay
- Functional Genomics Unit, Institut Pasteur de Montevideo, 11400, Montevideo, Uruguay
| | - Analia Lima
- Analytical Biochemistry and Proteomics Unit, Instituto de Investigaciones Biológicas Clemente Estable/Institut Pasteur de Montevideo, 11400, Montevideo, Uruguay
| | - Andrés Addiego
- Immunovirology Lab, Institut Pasteur de Montevideo, 11400, Montevideo, Uruguay
| | - Rosario Durán
- Analytical Biochemistry and Proteomics Unit, Instituto de Investigaciones Biológicas Clemente Estable/Institut Pasteur de Montevideo, 11400, Montevideo, Uruguay
| | - Gonzalo Moratorio
- Experimental Evolution of Viruses, Institut Pasteur de Montevideo, 11400, Montevideo, Uruguay
- Laboratorio de Virología Molecular, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay
| | - Otto Pritsch
- Immunovirology Lab, Institut Pasteur de Montevideo, 11400, Montevideo, Uruguay
- Immunobiology Department School of Medicine, Universidad de la República, 11800, Montevideo, Uruguay
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2
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Azimi FC, Dean TT, Minari K, Basso LGM, Vance TDR, Serrão VHB. A Frame-by-Frame Glance at Membrane Fusion Mechanisms: From Viral Infections to Fertilization. Biomolecules 2023; 13:1130. [PMID: 37509166 PMCID: PMC10377500 DOI: 10.3390/biom13071130] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 07/09/2023] [Accepted: 07/12/2023] [Indexed: 07/30/2023] Open
Abstract
Viral entry and fertilization are distinct biological processes that share a common mechanism: membrane fusion. In viral entry, enveloped viruses attach to the host cell membrane, triggering a series of conformational changes in the viral fusion proteins. This results in the exposure of a hydrophobic fusion peptide, which inserts into the host membrane and brings the viral and host membranes into close proximity. Subsequent structural rearrangements in opposing membranes lead to their fusion. Similarly, membrane fusion occurs when gametes merge during the fertilization process, though the exact mechanism remains unclear. Structural biology has played a pivotal role in elucidating the molecular mechanisms underlying membrane fusion. High-resolution structures of the viral and fertilization fusion-related proteins have provided valuable insights into the conformational changes that occur during this process. Understanding these mechanisms at a molecular level is essential for the development of antiviral therapeutics and tools to influence fertility. In this review, we will highlight the biological importance of membrane fusion and how protein structures have helped visualize both common elements and subtle divergences in the mechanisms behind fusion; in addition, we will examine the new tools that recent advances in structural biology provide researchers interested in a frame-by-frame understanding of membrane fusion.
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Affiliation(s)
- Farshad C. Azimi
- Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada;
| | - Trevor T. Dean
- Pharmaceutical Sciences, University of Illinois Chicago, Chicago, IL 60612, USA;
| | - Karine Minari
- Biomolecular Cryo-Electron Microscopy Facility, University of California-Santa Cruz, Santa Cruz, CA 95064, USA;
| | - Luis G. M. Basso
- Laboratório de Ciências Físicas, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, Rio de Janeiro 28013-602, Brazil;
| | - Tyler D. R. Vance
- Department of Laboratory Medicine and Pathobiology, Temerty Faculty of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada;
| | - Vitor Hugo B. Serrão
- Biomolecular Cryo-Electron Microscopy Facility, University of California-Santa Cruz, Santa Cruz, CA 95064, USA;
- Department of Chemistry and Biochemistry, University of California-Santa Cruz, Santa Cruz, CA 95064, USA
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3
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Hogan V, Johnson WE. Unique Structure and Distinctive Properties of the Ancient and Ubiquitous Gamma-Type Envelope Glycoprotein. Viruses 2023; 15:v15020274. [PMID: 36851488 PMCID: PMC9967133 DOI: 10.3390/v15020274] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Revised: 01/13/2023] [Accepted: 01/15/2023] [Indexed: 01/20/2023] Open
Abstract
After the onset of the AIDS pandemic, HIV-1 (genus Lentivirus) became the predominant model for studying retrovirus Env glycoproteins and their role in entry. However, HIV Env is an inadequate model for understanding entry of viruses in the Alpharetrovirus, Gammaretrovirus and Deltaretrovirus genera. For example, oncogenic model system viruses such as Rous sarcoma virus (RSV, Alpharetrovirus), murine leukemia virus (MLV, Gammaretrovirus) and human T-cell leukemia viruses (HTLV-I and HTLV-II, Deltaretrovirus) encode Envs that are structurally and functionally distinct from HIV Env. We refer to these as Gamma-type Envs. Gamma-type Envs are probably the most widespread retroviral Envs in nature. They are found in exogenous and endogenous retroviruses representing a broad spectrum of vertebrate hosts including amphibians, birds, reptiles, mammals and fish. In endogenous form, gamma-type Envs have been evolutionarily coopted numerous times, most notably as placental syncytins (e.g., human SYNC1 and SYNC2). Remarkably, gamma-type Envs are also found outside of the Retroviridae. Gp2 proteins of filoviruses (e.g., Ebolavirus) and snake arenaviruses in the genus Reptarenavirus are gamma-type Env homologs, products of ancient recombination events involving viruses of different Baltimore classes. Distinctive hallmarks of gamma-type Envs include a labile disulfide bond linking the surface and transmembrane subunits, a multi-stage attachment and fusion mechanism, a highly conserved (but poorly understood) "immunosuppressive domain", and activation by the viral protease during virion maturation. Here, we synthesize work from diverse retrovirus model systems to illustrate these distinctive properties and to highlight avenues for further exploration of gamma-type Env structure and function.
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Fló M, Carrión F, Olivero-Deibe N, Bianchi S, Portela M, Rammauro F, Alvarez B, Pritsch O. Kinetics of Bovine leukemia virus aspartic protease reveals its dimerization and conformational change. PLoS One 2022; 17:e0271671. [PMID: 35867649 PMCID: PMC9307154 DOI: 10.1371/journal.pone.0271671] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2022] [Accepted: 07/05/2022] [Indexed: 11/28/2022] Open
Abstract
The retropepsin (PR) of the Bovine leukemia virus (BLV) plays, as in other retroviruses, a crucial role in the transition from the non-infective viral particle to the infective virion by processing the polyprotein Gag. PR is expressed as an immature precursor associated with Gag, after an occasional −1 ribosomal frameshifting event. Self-hydrolysis of PR at specific N- and C-terminal sites releases the monomer that dimerizes giving rise to the active protease. We designed a strategy to express BLV PR in E. coli as a fusion protein with maltose binding protein, with a six-histidine tag at its N-terminal end, and bearing a tobacco etch virus protease hydrolysis site. This allowed us to obtain soluble and mature recombinant PR in relatively good yields, with exactly the same amino acid composition as the native protein. As PR presents relative promiscuity for the hydrolysis sites we designed four fluorogenic peptide substrates based on Förster resonance energy transfer (FRET) in order to characterize the activity of the recombinant enzyme. These substrates opened the way to perform kinetic studies, allowing us to characterize the dimer-monomer equilibrium. Furthermore, we obtained kinetic evidence for the existence of a conformational change that enables the interaction with the substrate. These results constitute a starting point for the elucidation of the kinetic properties of BLV-PR, and may be relevant not only to improve the chemical warfare against this virus but also to better understand other viral PRs.
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Affiliation(s)
- Martín Fló
- Laboratorio de Inmunovirología, Institut Pasteur de Montevideo, Montevideo, Uruguay
- Departamento de Inmunobiología, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
- * E-mail: (OP); (MF)
| | - Federico Carrión
- Laboratorio de Inmunovirología, Institut Pasteur de Montevideo, Montevideo, Uruguay
| | | | - Sergio Bianchi
- Laboratorio de Inmunovirología, Institut Pasteur de Montevideo, Montevideo, Uruguay
- Laboratorio de Biomarcadores Moleculares, Departamento de Fisiopatología, Hospital de Clínicas, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| | - Madelón Portela
- Unidad de Bioquímica y Proteómica Analíticas, Institut Pasteur de Montevideo, Facultad de Ciencias, Montevideo, Uruguay
| | - Florencia Rammauro
- Laboratorio de Inmunovirología, Institut Pasteur de Montevideo, Montevideo, Uruguay
- Departamento de Inmunobiología, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| | - Beatriz Alvarez
- Laboratorio de Enzimología, Instituto de Química Biológica, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay
| | - Otto Pritsch
- Laboratorio de Inmunovirología, Institut Pasteur de Montevideo, Montevideo, Uruguay
- Departamento de Inmunobiología, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
- * E-mail: (OP); (MF)
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Cerón Téllez F, González Méndez AS, Tórtora Pérez JL, Loza-Rubio E, Ramírez Álvarez H. Lack of association between amino acid sequences of the bovine leukemia virus envelope and varying stages of infection in dairy cattle. Virus Res 2020; 278:197866. [PMID: 31968223 DOI: 10.1016/j.virusres.2020.197866] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2019] [Revised: 01/15/2020] [Accepted: 01/15/2020] [Indexed: 02/05/2023]
Abstract
We collected 724 blood samples from dairy cattle from six Mexican states, and tested them for the presence of antibodies against BLV using a commercial ELISA test. Our study groups consisted of 32 samples: 12 asymptomatic cows, 12 cows with lymphocytosis and 8 samples of tumor tissue of the abomasum and heart of cattle with lymphoma. We designed three pairs of primers to amplify the complete BLV env gene, and obtained a fragment of 1548 nucleotides in length with the sequenced products. According to the phylogenetic tree we constructed to identify the viral genotype, 96.87 % of the sequences grouped into genotype 1, while a single sample from a cow with lymphocytosis (3.13 %) was associated with genotype 3 sequences. The similarity between the Mexican BLV sequences ranged from 0.985-1.00. In addition, the proportion of non-synonymous and synonymous mutations indicated negative selection. We did not identify any conserved residues in the viral protein sequences that could be related to BLV infection stage in cattle. Proviral quantification was performed using quantitative polymerase chain reaction, and we used Mood´s median test as statistical analysis. We found no significant association between proviral load and phase of infection. The sequences showed high similarity without any association between BLV surface glycoprotein and the different infection stages, nor differences in the proviral load. BLV genotype 1 was identified as prevalent in the studied samples, and for the first time in Mexico, we identified BLV genotype 3 in cattle.
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Affiliation(s)
- Fernando Cerón Téllez
- Virology, Genetics and Molecular Biology Laboratory, Faculty of Higher Education, Cuautitlan, Veterinary Medicine, Campus 4, National Autonomous University of Mexico, Km. 2.5 Carretera Cuautitlán-Teoloyucan San Sebastián Xhala, Cuautitlán Izcalli Estado de México, C.P. 54714, Mexico.
| | - Ana Silvia González Méndez
- Virology, Genetics and Molecular Biology Laboratory, Faculty of Higher Education, Cuautitlan, Veterinary Medicine, Campus 4, National Autonomous University of Mexico, Km. 2.5 Carretera Cuautitlán-Teoloyucan San Sebastián Xhala, Cuautitlán Izcalli Estado de México, C.P. 54714, Mexico.
| | - Jorge Luis Tórtora Pérez
- Virology, Genetics and Molecular Biology Laboratory, Faculty of Higher Education, Cuautitlan, Veterinary Medicine, Campus 4, National Autonomous University of Mexico, Km. 2.5 Carretera Cuautitlán-Teoloyucan San Sebastián Xhala, Cuautitlán Izcalli Estado de México, C.P. 54714, Mexico.
| | - Elizabeth Loza-Rubio
- National Center of Research in Animal Microbiology and Innocuity, INIFAP, CP. 05110, Mexico City, Mexico.
| | - Hugo Ramírez Álvarez
- Virology, Genetics and Molecular Biology Laboratory, Faculty of Higher Education, Cuautitlan, Veterinary Medicine, Campus 4, National Autonomous University of Mexico, Km. 2.5 Carretera Cuautitlán-Teoloyucan San Sebastián Xhala, Cuautitlán Izcalli Estado de México, C.P. 54714, Mexico.
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6
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X-ray Structures of the Post-fusion 6-Helix Bundle of the Human Syncytins and their Functional Implications. J Mol Biol 2019; 431:4922-4940. [PMID: 31711961 PMCID: PMC7094397 DOI: 10.1016/j.jmb.2019.10.020] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Revised: 10/22/2019] [Accepted: 10/23/2019] [Indexed: 12/27/2022]
Abstract
The retroviral envelope-derived proteins syncytin-1 and syncytin-2 (syn1 and syn2) drive placentation in humans by forming a syncytiotophoblast, a structure allowing for an exchange interface between maternal and fetal blood during pregnancy. Despite their essential role, little is known about the molecular mechanism underlying the syncytins' function. We report here the X-ray structures of the syn1 and syn2 transmembrane subunit ectodomains, featuring a 6-helix bundle (6HB) typical of the post-fusion state of gamma-retrovirus and filovirus fusion proteins. Contrary to the filoviruses, for which the fusion glycoprotein was crystallized both in the post-fusion and in the spring-loaded pre-fusion form, the highly unstable nature of the syncytins' prefusion form has precluded structural studies. We undertook a proline-scanning approach searching for regions in the syn1 6HB central helix that tolerate the introduction of helix-breaker residues and still fold correctly in the pre-fusion form. We found that there is indeed such a region, located two α-helical turns downstream a stutter in the central coiled-coil helix - precisely where the breaks of the spring-loaded helix of the filoviruses map. These mutants were fusion-inactive as they cannot form the 6HB, similar to the “SOSIP” mutant of HIV Env that allowed the high-resolution structural characterization of its labile pre-fusion form. These results now open a new window of opportunity to engineer more stable variants of the elusive pre-fusion trimer of the syncytins and other gamma-retroviruses envelope proteins for structural characterization. A typical retroviral γ-type Env protein 6-helix bundle in post-fusion syncytins. An extensive ionic interactions network correlates with higher stability of syn1. Spring-loaded pre-fusion form hinted by structural homology with filoviruses. Helix-breaking residues in the central coiled-coil allow folding in pre-fusion form.
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Corredor AP, González J, Baquero LA, Curtidor H, Olaya-Galán NN, Patarroyo MA, Gutiérrez MF. In silico and in vitro analysis of boAP3d1 protein interaction with bovine leukaemia virus gp51. PLoS One 2018; 13:e0199397. [PMID: 29928016 PMCID: PMC6013181 DOI: 10.1371/journal.pone.0199397] [Citation(s) in RCA: 11] [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: 03/27/2018] [Accepted: 06/06/2018] [Indexed: 11/19/2022] Open
Abstract
The envelope glycoprotein 51 (gp51) is essential for bovine leukaemia virus (BLV) entry to bovine B-lymphocytes. Although the bovine adaptor protein 3 complex subunit delta-1 (boAP3D1) has been proposed as the potential receptor, the specific ligand-receptor interaction has not yet been completely defined and boAP3D1 receptor and gp51 3D structures have not been determined. This study was thus aimed at a functional annotation of boAP3D1 cellular adaptor protein and BLV gp51 and, proposing a reliable model for gp51-AP3D1 interaction using bioinformatics tools. The boAP3D1 receptor interaction patterns were calculated based on models of boAP3D1 receptor and gp51 complexes’ 3D structures, which were constructed using homology techniques and data-driven docking strategy. The results showed that the participation of 6 key amino acids (aa) on gp51 (Asn170, Trp127, His115, Ala97, Ser98 and Glu128) and 4 aa on AP3D1 (Lys925, Asp807, Asp695 and Arg800) was highly probable in the interaction between gp51 and BLVR domains. Three gp51 recombinant peptides were expressed and purified to validate these results: the complete domain (rgp51), the N-terminal portion (rNgp51) and the C-terminal fragment (rCgp51); and binding assays to Madin-Darby bovine kidney (MDBK) cells were then carried out with each recombinant. It was found that rNgp51 preferentially bound to MDBK cells, suggesting this domain’s functional role during invasion. The rNgp51-MDBK cell interaction was sensitive to trypsin (98% reduction) and chymotrypsin treatment (80% reduction). These results highlighted that the N-terminal portion of gp51 interacted in vitro with the AP3D1 receptor and provides a plausible in silico interaction model.
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Affiliation(s)
| | - Janneth González
- Nutrition and Biochemistry Department, Science Faculty, Universidad Javeriana, Bogotá DC, Colombia
- * E-mail: (MFG); (JG)
| | - Luis Alfredo Baquero
- Molecular Biology and Immunology Department, Fundación Instituto de Inmunología de Colombia (FIDIC), Bogotá DC, Colombia
| | - Hernando Curtidor
- Molecular Biology and Immunology Department, Fundación Instituto de Inmunología de Colombia (FIDIC), Bogotá DC, Colombia
- Basic Sciences Department, School of Medicine and Health Sciences, Universidad del Rosario, Bogotá DC, Colombia
| | - Nury Nathalia Olaya-Galán
- Virology Laboratory, Universidad Javeriana, Bogotá DC, Colombia
- PhD Programme in Biomedical and Biological Sciences, Universidad del Rosario, Bogotá DC, Colombia
| | - Manuel Alfonso Patarroyo
- Molecular Biology and Immunology Department, Fundación Instituto de Inmunología de Colombia (FIDIC), Bogotá DC, Colombia
- Basic Sciences Department, School of Medicine and Health Sciences, Universidad del Rosario, Bogotá DC, Colombia
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8
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Waugh DS. Crystal structures of MBP fusion proteins. Protein Sci 2016; 25:559-71. [PMID: 26682969 DOI: 10.1002/pro.2863] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Accepted: 12/16/2015] [Indexed: 02/06/2023]
Abstract
Although chaperone-assisted protein crystallization remains a comparatively rare undertaking, the number of crystal structures of polypeptides fused to maltose-binding protein (MBP) that have been deposited in the Protein Data Bank (PDB) has grown dramatically during the past decade. Altogether, 102 fusion protein structures were detected by Basic Local Alignment Search Tool (BLAST) analysis. Collectively, these structures comprise a range of sizes, space groups, and resolutions that are typical of the PDB as a whole. While most of these MBP fusion proteins were equipped with short inter-domain linkers to increase their rigidity, fusion proteins with long linkers have also been crystallized. In some cases, surface entropy reduction mutations in MBP appear to have facilitated the formation of crystals. A comparison of the structures of fused and unfused proteins, where both are available, reveals that MBP-mediated structural distortions are very rare.
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Affiliation(s)
- David S Waugh
- Protein Engineering Section, Macromolecular Crystallography Laboratory, Center for Cancer Research, National Cancer Institute at Frederick, P.O. Box B, Frederick, Maryland, 21702-1201
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Kiselev OI, Vasin AV, Shevyryova MP, Deeva EG, Sivak KV, Egorov VV, Tsvetkov VB, Egorov AY, Romanovskaya-Romanko EA, Stepanova LA, Komissarov AB, Tsybalova LM, Ignatjev GM. Ebola hemorrhagic fever: Properties of the pathogen and development of vaccines and chemotherapeutic agents. Mol Biol 2015; 49:480-493. [PMID: 32214474 PMCID: PMC7089462 DOI: 10.1134/s002689331504007x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2014] [Accepted: 01/16/2015] [Indexed: 11/22/2022]
Abstract
Ebola hemorrhagic fever (EHF) epidemic currently ongoing in West Africa is not the first among numerous epidemics in the continent. Yet it seems to be the worst EHF epidemic outbreak caused by Ebola virus Zaire since 1976 as regards its extremely large scale and rapid spread in the population. Experiments to study the agent have continued for more than 20 years. The EHF virus has a relatively simple genome with seven genes and additional reading frame resulting from RNA editing. While being of a relatively low genetic capacity, the virus can be ranked as a standard for pathogenicity with the ability to evade the host immune response in uttermost perfection. The EHF virus has similarities with retroviruses, but belongs to (-)RNA viruses of a nonretroviral origin. Genetic elements of the virus, NIRV, were detected in animal and human genomes. EHF virus glycoprotein (GP) is a class I fusion protein and shows more similarities than distinctions in tertiary structure with SIV and HIV gp41 proteins and even influenza virus hemagglutinin. EHF is an unusual infectious disease, and studying the molecular basis of its pathogenesis may contribute to new findings in therapy of severe conditions leading to a fatal outcome.
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Affiliation(s)
- O. I. Kiselev
- Institute of Influenza, Ministry of Health of the Russian Federation, St. Petersburg, 197376 Russia
| | - A. V. Vasin
- Institute of Influenza, Ministry of Health of the Russian Federation, St. Petersburg, 197376 Russia
- St. Petersburg State Polytechnic University, St. Petersburg, 195251 Russia
| | - M. P. Shevyryova
- Ministry of Health of the Russian Federation, Moscow, 127994 Russia
| | - E. G. Deeva
- Institute of Influenza, Ministry of Health of the Russian Federation, St. Petersburg, 197376 Russia
| | - K. V. Sivak
- Institute of Influenza, Ministry of Health of the Russian Federation, St. Petersburg, 197376 Russia
| | - V. V. Egorov
- Institute of Influenza, Ministry of Health of the Russian Federation, St. Petersburg, 197376 Russia
| | - V. B. Tsvetkov
- Institute of Influenza, Ministry of Health of the Russian Federation, St. Petersburg, 197376 Russia
- Topchiev Institute of Petrochemical Synthesis, Moscow, 119991 Russia
| | - A. Yu. Egorov
- Institute of Influenza, Ministry of Health of the Russian Federation, St. Petersburg, 197376 Russia
| | | | - L. A. Stepanova
- Institute of Influenza, Ministry of Health of the Russian Federation, St. Petersburg, 197376 Russia
| | - A. B. Komissarov
- Institute of Influenza, Ministry of Health of the Russian Federation, St. Petersburg, 197376 Russia
| | - L. M. Tsybalova
- Institute of Influenza, Ministry of Health of the Russian Federation, St. Petersburg, 197376 Russia
| | - G. M. Ignatjev
- Institute of Influenza, Ministry of Health of the Russian Federation, St. Petersburg, 197376 Russia
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10
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Ishida Y, McCallister C, Nikolaidis N, Tsangaras K, Helgen KM, Greenwood AD, Roca AL. Sequence variation of koala retrovirus transmembrane protein p15E among koalas from different geographic regions. Virology 2014; 475:28-36. [PMID: 25462343 DOI: 10.1016/j.virol.2014.10.036] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2014] [Revised: 09/04/2014] [Accepted: 10/28/2014] [Indexed: 11/30/2022]
Abstract
The koala retrovirus (KoRV), which is transitioning from an exogenous to an endogenous form, has been associated with high mortality in koalas. For other retroviruses, the envelope protein p15E has been considered a candidate for vaccine development. We therefore examined proviral sequence variation of KoRV p15E in a captive Queensland and three wild southern Australian koalas. We generated 163 sequences with intact open reading frames, which grouped into 39 distinct haplotypes. Sixteen distinct haplotypes comprising 139 of the sequences (85%) coded for the same polypeptide. Among the remaining 23 haplotypes, 22 were detected only once among the sequences, and each had 1 or 2 non-synonymous differences from the majority sequence. Several analyses suggested that p15E was under purifying selection. Important epitopes and domains were highly conserved across the p15E sequences and in previously reported exogenous KoRVs. Overall, these results support the potential use of p15E for KoRV vaccine development.
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Affiliation(s)
- Yasuko Ishida
- Department of Animal Sciences, University of Illinois at Urbana-Champaign, 1207 W. Gregory Drive, Urbana, IL 61801, USA.
| | - Chelsea McCallister
- Department of Biological Science and Center for Applied Biotechnology Studies, California State University, Fullerton, 800 North State College Blvd, Fullerton, CA 92834, USA.
| | - Nikolas Nikolaidis
- Department of Biological Science and Center for Applied Biotechnology Studies, California State University, Fullerton, 800 North State College Blvd, Fullerton, CA 92834, USA.
| | - Kyriakos Tsangaras
- Leibniz Institute for Zoo and Wildlife Research, Alfred-Kowalke-Str. 17, 10315, Berlin, Germany.
| | - Kristofer M Helgen
- National Museum of Natural History, Smithsonian Institution, PO Box 37012, MRC 108, Washington, DC 20013, USA.
| | - Alex D Greenwood
- Leibniz Institute for Zoo and Wildlife Research, Alfred-Kowalke-Str. 17, 10315, Berlin, Germany.
| | - Alfred L Roca
- Department of Animal Sciences, University of Illinois at Urbana-Champaign, 1207 W. Gregory Drive, Urbana, IL 61801, USA; The Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
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11
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Fedotova MV, Kruchinin SE. Ion-binding of glycine zwitterion with inorganic ions in biologically relevant aqueous electrolyte solutions. Biophys Chem 2014; 190-191:25-31. [DOI: 10.1016/j.bpc.2014.04.001] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Revised: 04/02/2014] [Accepted: 04/02/2014] [Indexed: 11/29/2022]
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12
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Structural characterization of the glycoprotein GP2 core domain from the CAS virus, a novel arenavirus-like species. J Mol Biol 2013; 426:1452-68. [PMID: 24333483 PMCID: PMC3951589 DOI: 10.1016/j.jmb.2013.12.009] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2013] [Revised: 12/02/2013] [Accepted: 12/04/2013] [Indexed: 11/21/2022]
Abstract
Fusion of the viral and host cell membranes is a necessary first step for infection by enveloped viruses and is mediated by the envelope glycoprotein. The transmembrane subunits from the structurally defined “class I” glycoproteins adopt an α-helical “trimer-of-hairpins” conformation during the fusion pathway. Here, we present our studies on the envelope glycoprotein transmembrane subunit, GP2, of the CAS virus (CASV). CASV was recently identified from annulated tree boas (Corallus annulatus) with inclusion body disease and is implicated in the disease etiology. We have generated and characterized two protein constructs consisting of the predicted CASV GP2 core domain. The crystal structure of the CASV GP2 post-fusion conformation indicates a trimeric α-helical bundle that is highly similar to those of Ebola virus and Marburg virus GP2 despite CASV genome homology to arenaviruses. Denaturation studies demonstrate that the stability of CASV GP2 is pH dependent with higher stability at lower pH; we propose that this behavior is due to a network of interactions among acidic residues that would destabilize the α-helical bundle under conditions where the side chains are deprotonated. The pH-dependent stability of the post-fusion structure has been observed in Ebola virus and Marburg virus GP2, as well as other viruses that enter via the endosome. Infection experiments with CASV and the related Golden Gate virus support a mechanism of entry that requires endosomal acidification. Our results suggest that, despite being primarily arenavirus like, the transmembrane subunit of CASV is extremely similar to the filoviruses. CASV is a novel arenavirus with a filovirus-like glycoprotein. Arenaviruses and filoviruses are significant human pathogens. The stability of the CASV GP2 post-fusion structure is dependent on pH. CASV infection requires endosomal acidification. The structure and function of CASV GP2 is similar to filovirus GP2.
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Crystal structures of beta- and gammaretrovirus fusion proteins reveal a role for electrostatic stapling in viral entry. J Virol 2013; 88:143-53. [PMID: 24131724 DOI: 10.1128/jvi.02023-13] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Membrane fusion is a key step in the life cycle of all envelope viruses, but this process is energetically unfavorable; the transmembrane fusion subunit (TM) of the virion-attached glycoprotein actively catalyzes the membrane merger process. Retroviral glycoproteins are the prototypical system to study pH-independent viral entry. In this study, we determined crystal structures of extramembrane regions of the TMs from Mason-Pfizer monkey virus (MPMV) and xenotropic murine leukemia virus-related virus (XMRV) at 1.7-Å and 2.2-Å resolution, respectively. The structures are comprised of a trimer of hairpins that is characteristic of class I viral fusion proteins and now completes a structural library of retroviral fusion proteins. Our results allowed us to identify a series of intra- and interchain electrostatic interactions in the heptad repeat and chain reversal regions. Mutagenesis reveals that charge-neutralizing salt bridge mutations significantly destabilize the postfusion six-helix bundle and abrogate retroviral infection, demonstrating that electrostatic stapling of the fusion subunit is essential for viral entry. Our data indicate that salt bridges are a major stabilizing force on the MPMV and XMRV retroviral TMs and likely provide the key energetics for viral and host membrane fusion.
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Aydin H, Smrke BM, Lee JE. Structural characterization of a fusion glycoprotein from a retrovirus that undergoes a hybrid 2-step entry mechanism. FASEB J 2013; 27:5059-71. [PMID: 24036886 PMCID: PMC7164122 DOI: 10.1096/fj.13-232371] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Entry of enveloped viruses into host cells is mediated by their surface envelope glycoproteins (Env). On the surface of the virus, Env is in a metastable, prefusion state, primed to catalyze the fusion of the viral and host membranes. An external trigger is needed to promote the drastic conformational changes necessary for the fusion subunit to fold into the low‐energy, 6‐helix bundle. These triggers typically facilitate pH‐independent entry at the plasma membrane or pH‐dependent entry in a low‐pH endosomal compartment. The α‐retrovirus avian sarcoma leukosis virus (ASLV) has a rare, 2‐step entry mechanism with both pH‐dependent and pH‐independent features. Here, we present the 2.0‐Å‐resolution crystal structure of the ASLV transmembrane (TM) fusion protein. Our structural and biophysical studies indicated that unlike other pH‐dependent or pH‐independent viral TMs, the ASLV fusion subunit is stable irrespective of pH. Two histidine residues (His490 and His492) in the chain reversal region confer stability at low pH. A structural comparison of class I viral fusion proteins suggests that the presence of a positive charge, either a histidine or arginine amino acid, stabilizes a helical dipole moment and is a signature of fusion proteins active at low pH. The structure now reveals key residues and features that explain its 2‐step mechanism, and we discuss the implications of the ASLV TM structure in the context of general mechanisms required for membrane fusion.—Aydin, H., Smrke, B.M., Lee, J. E. Structural characterization of a fusion glycoprotein from a retrovirus that undergoes a hybrid 2‐step entry mechanism. FASEB J. 27, 5059–5071 (2013). http://www.fasebj.org
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Affiliation(s)
- Halil Aydin
- 11 King's College Cir., Rm. 6316, Toronto, ON, Canada M5S 1A8.
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15
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Moratorio G, Fischer S, Bianchi S, Tomé L, Rama G, Obal G, Carrión F, Pritsch O, Cristina J. A detailed molecular analysis of complete bovine leukemia virus genomes isolated from B-cell lymphosarcomas. Vet Res 2013; 44:19. [PMID: 23506507 PMCID: PMC3618307 DOI: 10.1186/1297-9716-44-19] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Accepted: 01/30/2013] [Indexed: 01/08/2023] Open
Abstract
It is widely accepted that the majority of cancers result from multiple cellular events leading to malignancy after a prolonged period of clinical latency, and that the immune system plays a critical role in the control of cancer progression. Bovine leukemia virus (BLV) is an oncogenic member of the Retroviridae family. Complete genomic sequences of BLV strains isolated from peripheral blood mononuclear cells (PBMC) from cattle have been previously reported. However, a detailed characterization of the complete genome of BLV strains directly isolated from bovine tumors is much needed in order to contribute to the understanding of the mechanisms of leukemogenesis induced by BLV in cattle. In this study, we performed a molecular characterization of BLV complete genomes from bovine B-cell lymphosarcoma isolates. A nucleotide substitution was found in the glucocorticoid response element (GRE) site of the 5' long terminal repeat (5'LTR) of the BLV isolates. All amino acid substitutions in Tax previously found to be related to stimulate high transcriptional activity of 5'LTR were not found in these studies. Amino acid substitutions were found in the nucleocapsid, gp51 and G4 proteins. Premature stop-codons in R3 were observed. Few mutations or amino acid substitutions may be needed to allow BLV provirus to achieve silencing. Substitutions that favor suppression of viral expression in malignant B cells might be a strategy to circumvent effective immune attack.
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Affiliation(s)
- Gonzalo Moratorio
- Laboratorio de Virología Molecular, Centro de Investigaciones Nucleares, Facultad de Ciencias, Universidad de la República, Iguá 4225, Montevideo 11400, Uruguay.
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Collins KD. Why continuum electrostatics theories cannot explain biological structure, polyelectrolytes or ionic strength effects in ion–protein interactions. Biophys Chem 2012; 167:43-59. [DOI: 10.1016/j.bpc.2012.04.002] [Citation(s) in RCA: 169] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2011] [Revised: 04/10/2012] [Accepted: 04/10/2012] [Indexed: 01/13/2023]
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