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Open data
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Basic information
| Entry | Database: PDB / ID: 9cu4 | ||||||||||||||||||||||||||||||||||||||||||
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| Title | KSHV glycoprotein B ectodomain, postfusion form | ||||||||||||||||||||||||||||||||||||||||||
Components | ORF8 | ||||||||||||||||||||||||||||||||||||||||||
Keywords | VIRAL PROTEIN / Membrane fusion | ||||||||||||||||||||||||||||||||||||||||||
| Function / homology | Function and homology informationhost cell endosome / host cell Golgi apparatus / viral envelope / symbiont entry into host cell / virion attachment to host cell / host cell plasma membrane / membrane Similarity search - Function | ||||||||||||||||||||||||||||||||||||||||||
| Biological species | ![]() Human gammaherpesvirus 8 | ||||||||||||||||||||||||||||||||||||||||||
| Method | ELECTRON MICROSCOPY / single particle reconstruction / cryo EM / Resolution: 3.3 Å | ||||||||||||||||||||||||||||||||||||||||||
Authors | Ito, F. / Zhen, J. / Xie, G. / Huang, H. / Silva, J.C. / Wu, T. / Zhou, Z.H. | ||||||||||||||||||||||||||||||||||||||||||
| Funding support | United States, 1items
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Citation | Journal: J Virol / Year: 2025Title: Structure of the Kaposi's sarcoma-associated herpesvirus gB in post-fusion conformation. Authors: Fumiaki Ito / James Zhen / Guodong Xie / Haigen Huang / Juan C Silva / Ting-Ting Wu / Z Hong Zhou / ![]() Abstract: Discovered in 1994 in lesions of an AIDS patient, Kaposi's sarcoma-associated herpesvirus (KSHV) is a member of the gammaherpesvirus subfamily of the family, which contains a total of nine that ...Discovered in 1994 in lesions of an AIDS patient, Kaposi's sarcoma-associated herpesvirus (KSHV) is a member of the gammaherpesvirus subfamily of the family, which contains a total of nine that infect humans. These viruses all contain a large envelope glycoprotein, glycoprotein B (gB), that is required for viral fusion with host cell membrane to initial infection. Although the atomic structures of five other human herpesviruses in their postfusion conformation and one in its prefusion conformation are known, the atomic structure of KSHV gB has not been reported. Here, we report the first structure of the KSHV gB ectodomain determined by single-particle cryogenic electron microscopy (cryoEM). Despite a similar global fold between herpesvirus gB, KSHV gB possesses local differences not shared by its relatives in other herpesviruses. The glycosylation sites of gB are arranged in belts down the symmetry axis with distinct localization compared to that of other herpesviruses, which occludes certain antibody binding sites. An extended glycan chain observed in domain I (DI), located proximal to the host membrane, may suggest its possible role in host cell attachment. Local flexibility of domain IV (DIV) governed by molecular hinges at its interdomain junctions identifies a means for enabling conformational change. A mutation in the domain III (DIII) central helix disrupts incorporation of gB into KSHV virions despite adoption of a canonical fold . Taken together, this study reveals mechanisms of structural variability of herpesvirus fusion protein gB and informs its folding and immunogenicity.IMPORTANCEIn 1994, a cancer-causing virus was discovered in lesions of AIDS patients, which was later named Kaposi's sarcoma-associated herpesvirus (KSHV). As the latest discovered human herpesvirus, KSHV has been classified into the gammaherpesvirus subfamily of the . In this study, we have expressed KSHV gB and employed cryogenic electron microscopy (cryoEM) to determine its first structure. Importantly, our structure resolves some glycans beyond the first sugar moiety. These glycans are arranged in a pattern unique to KSHV, which impacts the antigenicity of KSHV gB. Our structure also reveals conformational flexibility caused by molecular hinges between domains that provide clues into the mechanism behind the drastic change between prefusion and postfusion states. | ||||||||||||||||||||||||||||||||||||||||||
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Structure visualization
| Structure viewer | Molecule: Molmil Jmol/JSmol |
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Downloads & links
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Download
| PDBx/mmCIF format | 9cu4.cif.gz | 367.7 KB | Display | PDBx/mmCIF format |
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| PDB format | pdb9cu4.ent.gz | 301.4 KB | Display | PDB format |
| PDBx/mmJSON format | 9cu4.json.gz | Tree view | PDBx/mmJSON format | |
| Others | Other downloads |
-Validation report
| Summary document | 9cu4_validation.pdf.gz | 1.7 MB | Display | wwPDB validaton report |
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| Full document | 9cu4_full_validation.pdf.gz | 1.7 MB | Display | |
| Data in XML | 9cu4_validation.xml.gz | 68.1 KB | Display | |
| Data in CIF | 9cu4_validation.cif.gz | 100.8 KB | Display | |
| Arichive directory | https://data.pdbj.org/pub/pdb/validation_reports/cu/9cu4 ftp://data.pdbj.org/pub/pdb/validation_reports/cu/9cu4 | HTTPS FTP |
-Related structure data
| Related structure data | ![]() 45927MC M: map data used to model this data C: citing same article ( |
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| Similar structure data | Similarity search - Function & homology F&H Search |
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Links
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Assembly
| Deposited unit | ![]()
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Components
| #1: Protein | Mass: 71326.758 Da / Num. of mol.: 3 / Mutation: D470P Source method: isolated from a genetically manipulated source Source: (gene. exp.) ![]() Human gammaherpesvirus 8 / Gene: ORF8 / Production host: ![]() #2: Polysaccharide | #3: Polysaccharide | Source method: isolated from a genetically manipulated source #4: Sugar | ChemComp-NAG / Has ligand of interest | N | Has protein modification | Y | |
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-Experimental details
-Experiment
| Experiment | Method: ELECTRON MICROSCOPY |
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| EM experiment | Aggregation state: PARTICLE / 3D reconstruction method: single particle reconstruction |
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Sample preparation
| Component | Name: Ectodomain of KSHV glycoprotein B in postfusion form / Type: ORGANELLE OR CELLULAR COMPONENT / Entity ID: #1 / Source: RECOMBINANT |
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| Molecular weight | Value: 0.23 MDa / Experimental value: NO |
| Source (natural) | Organism: ![]() Human gammaherpesvirus 8 |
| Source (recombinant) | Organism: ![]() |
| Buffer solution | pH: 8 |
| Specimen | Embedding applied: NO / Shadowing applied: NO / Staining applied: NO / Vitrification applied: YES |
| Vitrification | Instrument: FEI VITROBOT MARK IV / Cryogen name: ETHANE-PROPANE / Humidity: 100 % / Chamber temperature: 277 K |
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Electron microscopy imaging
| Experimental equipment | ![]() Model: Titan Krios / Image courtesy: FEI Company |
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| Microscopy | Model: TFS KRIOS |
| Electron gun | Electron source: FIELD EMISSION GUN / Accelerating voltage: 300 kV / Illumination mode: FLOOD BEAM |
| Electron lens | Mode: BRIGHT FIELD / Nominal magnification: 105000 X / Nominal defocus max: 2800 nm / Nominal defocus min: 800 nm / Cs: 2.7 mm |
| Image recording | Electron dose: 50 e/Å2 / Film or detector model: GATAN K3 BIOQUANTUM (6k x 4k) / Num. of grids imaged: 1 / Num. of real images: 14633 |
| Image scans | Width: 4092 / Height: 5760 |
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Processing
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| CTF correction | Type: PHASE FLIPPING AND AMPLITUDE CORRECTION | ||||||||||||||||
| Symmetry | Point symmetry: C3 (3 fold cyclic) | ||||||||||||||||
| 3D reconstruction | Resolution: 3.3 Å / Resolution method: FSC 0.143 CUT-OFF / Num. of particles: 64516 / Num. of class averages: 1 / Symmetry type: POINT |
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Human gammaherpesvirus 8
United States, 1items
Citation
PDBj



FIELD EMISSION GUN