Variable Surface Epitopes in the Crystal Structure of Dengue Virus Type 3 Envelope Glycoprotein

Children's Hospital, Enders 673, 320 Longwood Ave., Boston, MA 02115, USA.
Journal of Virology (Impact Factor: 4.44). 02/2005; 79(2):1223-31. DOI: 10.1128/JVI.79.2.1223-1231.2005
Source: PubMed


Dengue virus is an emerging global health threat. The major envelope glycoprotein, E, mediates viral attachment and entry by membrane fusion. Antibodies that bind but fail to neutralize noncognate serotypes enhance infection. We have determined the crystal structure of a soluble fragment of the envelope glycoprotein E from dengue virus type 3. The structure closely resembles those of E proteins from dengue type 2 and tick-borne encephalitis viruses. Serotype-specific neutralization escape mutants in dengue virus E proteins are all located on a surface of domain III, which has been implicated in receptor binding. While antibodies against epitopes in domain I are nonneutralizing in dengue virus, there are neutralizing antibodies that recognize serotype-conserved epitopes in domain II. The mechanism of neutralization for these antibodies is probably inhibition of membrane fusion. Our structure shows that neighboring glycans on the viral surface are spaced widely enough (at least 32 A) that they can interact with multiple carbohydrate recognition domains on oligomeric lectins such as DC-SIGN, ensuring maximum affinity for these putative receptors.

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Available from: Yorgo Modis, Oct 06, 2015
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    • "Two alpha helices anchored in the viral membrane attach to E through a 53-residue C-terminal stem [6]. Domain III, at E's C-terminus, helps the virus target cell receptors, leading to endocytosis [7] [8] [9] [10] [11] [12] [13] [14]. Once inside the endosome, a low pH-driven conformational change of E results in exposure of hydrophobic residues at the tip of the beta-structured Domain II that attach E to the host endosomal membrane and promote virus–membrane fusion (Fig. 1) [15] [16]. "
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    ABSTRACT: Dengue virus is coated by an icosahedral shell of 90 envelope protein dimers that convert to trimers at low pH and promote fusion of its membrane with the membrane of the host endosome. We provide the first estimates for the free energy barrier and minimum for two key steps in this process: host membrane bending and protein-membrane binding. Both are studied using complementary membrane elastic, continuum electrostatics and all-atom molecular dynamics simulations. The predicted host membrane bending required to form an initial fusion stalk presents a 22-30 kcal/mol free energy barrier according to a constrained membrane elastic model. Combined continuum and molecular dynamics results predict a 15 kcal/mol free energy decrease on binding of each trimer of Dengue envelope protein to a membrane with 30% anionic phosphatidylglycerol lipid. The bending cost depends on the preferred curvature of the lipids composing the host membrane leaflets, while the free energy gained for protein binding depends on the surface charge density of the host membrane. The fusion loop of the envelope protein inserts exactly at the level of the interface between the membrane's hydrophobic and head-group regions. The methods used in this work provide a means for further characterization of the structures and free energies of protein-assisted membrane fusion. Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.
    Biochimica et Biophysica Acta (BBA) - Biomembranes 01/2015; 1848(4). DOI:10.1016/j.bbamem.2014.12.018 · 3.84 Impact Factor
    • "Ninety dimers of the envelope (E) protein cover the surface of the virus. The structure of the E protein has been solved by X-ray crystallography, either in a free state or in complex with an antibody (Modis et al., 2003; Zhang et al., 2004; Modis et al., 2005; Cockburn et al., 2012b). Each E protein monomer comprises three ectodomains, ED1 to ED3, and a transmembrane segment. "
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    ABSTRACT: Dengue fever is the most important vector-borne viral disease. Four serotypes of dengue virus, DENV1 to DENV4, coexist. Secondary infection by a different serotype is a risk factor for severe dengue. Monoclonal antibody mAb4E11 neutralizes the four serotypes of DENV with varying efficacies by recognizing an epitope located within domain-III (ED3) of the viral envelope (E) protein. To better understand the cross-reactivities between mAb4E11 and the four serotypes of DENV, we constructed mutations in both Fab4E11 fragment and ED3, and we searched for indirect interactions in the crystal structures of the four complexes. According to the serotype, 7 to 12 interactions are mediated by one water molecule, 1 to 10 by two water molecules, and several of these interactions are conserved between serotypes. Most interfacial water molecules make hydrogen bonds with both antibody and antigen. Some residues or atomic groups are engaged in both direct and water-mediated interactions. The doubly-indirect interactions are more numerous in the complex of lowest affinity. The third complementarity determining region of the light chain (L-CDR3) of mAb4E11 does not contact ED3. The structures and double-mutant thermodynamic cycles showed that the effects of (hyper)-mutations in L-CDR3 on affinity were caused by conformational changes and indirect interactions with ED3 through other CDRs. Exchanges of residues between ED3 serotypes showed that their effects on affinity were context dependent. Thus, conformational changes, structural context, and indirect interactions should be included when studying cross-reactivity between antibodies and different serotypes of viral antigens for a better design of diagnostics, vaccine, and therapeutic tools against DENV and other Flaviviruses. Copyright © 2014 John Wiley & Sons, Ltd.
    Journal of Molecular Recognition 04/2014; 27(4):205-14. DOI:10.1002/jmr.2352 · 2.15 Impact Factor
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    • "Further, a protein with molecular mass of 57 kDa was also purified by affinity chromatography using a DEN2-Sepharose 4B column [23]. Viral envelope (E) protein of DENV as other Flavivirus has a homology of about 40% among different members of the family [25], and the crystal structures of this protein revealed three domains (I, II, and III) containing significant structural conservation [26] [27] [28]. DENV E protein is a class II fusion protein responsible for host cell attachment, entry, and virusmediated cell membrane fusion. "
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    ABSTRACT: The main vector of dengue in America is the mosquito Aedes aegypti , which is infected by dengue virus (DENV) through receptors of midgut epithelial cells. The envelope protein (E) of dengue virus binds to receptors present on the host cells through its domain III that has been primarily recognized to bind cell receptors. In order to identify potential receptors, proteins from mosquito midgut tissue and C6/36 cells were purified by affinity using columns with the recombinant E protein domain III (rE-DIII) or DENV particles bound covalently to Sepharose 4B to compare and evaluate their performance to bind proteins including putative receptors from female mosquitoes of Ae. aegypti . To determine their identity mass spectrometric analysis of purified proteins separated by polyacrylamide gel electrophoresis was performed. Our results indicate that both viral particles and rE-DIII bound proteins with the same apparent molecular weights of 57 and 67 kDa. In addition, viral particles bound high molecular weight proteins. Purified proteins identified were enolase, beta-adrenergic receptor kinase (beta-ARK), translation elongation factor EF-1 alpha/Tu, and cadherin.
    11/2013; 2013(9105):875958. DOI:10.1155/2013/875958
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