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- PDB-8w5e: Cryo-EM structure of Qb-Ab4 -

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Basic information

Entry
Database: PDB / ID: 8w5e
TitleCryo-EM structure of Qb-Ab4
Components
  • Heavy chain of Ab4
  • Light chain of Ab4
  • Minor capsid protein A1
KeywordsIMMUNE SYSTEM / Qb / Antibody / cryo-EM
Function / homologyRead-through domain / Read-through domain / Levivirus coat protein / Levivirus coat protein / Bacteriophage RNA-type, capsid / viral capsid / structural molecule activity / Minor capsid protein A1
Function and homology information
Biological speciesMus musculus (house mouse)
Escherichia phage Qbeta (virus)
MethodELECTRON MICROSCOPY / single particle reconstruction / cryo EM / Resolution: 3.8 Å
AuthorsBao, K.Y. / Li, R.H. / Hua, Z.L. / Hou, B.D. / Zhu, P.
Funding support China, 4items
OrganizationGrant numberCountry
National Natural Science Foundation of China (NSFC)81991495 China
National Natural Science Foundation of China (NSFC)32241029 China
Chinese Academy of SciencesXDB29050600 China
Chinese Academy of SciencesXDB37010100 China
CitationJournal: Cell Rep / Year: 2025
Title: Competition propels, rather than limits, the success of low-affinity B cells in the germinal center response.
Authors: Runhan Li / Keyan Bao / Can Liu / Xuejing Ma / Zhaolin Hua / Ping Zhu / Baidong Hou /
Abstract: The germinal center (GC) sets an environment where antigen-specific B cells are compelled to continuously increase their affinity to compete for the antigen and obtain Tfh help for survival and ...The germinal center (GC) sets an environment where antigen-specific B cells are compelled to continuously increase their affinity to compete for the antigen and obtain Tfh help for survival and propagation. Previous studies indicated that low-affinity B cells are disadvantaged in the presence of high-affinity ones, suggesting that competition may lead to the elimination of low-affinity B cells and their descendants. However, using a multivalent virus-mimicking antigen, our study demonstrates that low-affinity B cells not only successfully participate in GC responses alongside high-affinity B cells but also undergo accelerated affinity maturation under the more stringent competition. Furthermore, our cryo-electron-microscopy-based structural analysis reveals that both low-affinity and high-affinity B cells compete for the same antigenic epitope. Although the applicability of this idealized GC competition to true pathogen-induced responses remains uncertain, this change in perspective on the role of competition in low-affinity B cell evolution provides valuable insights for vaccine development.
History
DepositionAug 26, 2023Deposition site: PDBJ / Processing site: PDBJ
Revision 1.0Feb 26, 2025Provider: repository / Type: Initial release
Revision 1.0Feb 26, 2025Data content type: EM metadata / Data content type: EM metadata / Provider: repository / Type: Initial release
Revision 1.0Feb 26, 2025Data content type: Half map / Part number: 1 / Data content type: Half map / Provider: repository / Type: Initial release
Revision 1.0Feb 26, 2025Data content type: Half map / Part number: 2 / Data content type: Half map / Provider: repository / Type: Initial release
Revision 1.0Feb 26, 2025Data content type: Image / Data content type: Image / Provider: repository / Type: Initial release
Revision 1.0Feb 26, 2025Data content type: Primary map / Data content type: Primary map / Provider: repository / Type: Initial release

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Structure visualization

Structure viewerMolecule:
MolmilJmol/JSmol

Downloads & links

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Assembly

Deposited unit
H: Heavy chain of Ab4
c: Minor capsid protein A1
C: Minor capsid protein A1
L: Light chain of Ab4


Theoretical massNumber of molelcules
Total (without water)54,4934
Polymers54,4934
Non-polymers00
Water00
1


  • Idetical with deposited unit
  • defined by author&software
  • Evidence: electron microscopy, not applicable
TypeNameSymmetry operationNumber
identity operation1_555x,y,z1

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Components

#1: Antibody Heavy chain of Ab4


Mass: 13855.258 Da / Num. of mol.: 1
Source method: isolated from a genetically manipulated source
Source: (gene. exp.) Mus musculus (house mouse) / Production host: Homo sapiens (human)
#2: Protein Minor capsid protein A1 / Qb coat protein


Mass: 14268.071 Da / Num. of mol.: 2
Source method: isolated from a genetically manipulated source
Source: (gene. exp.) Escherichia phage Qbeta (virus) / Production host: Escherichia coli (E. coli) / References: UniProt: Q8LTE1
#3: Antibody Light chain of Ab4


Mass: 12101.261 Da / Num. of mol.: 1
Source method: isolated from a genetically manipulated source
Source: (gene. exp.) Mus musculus (house mouse) / Production host: Homo sapiens (human)
Has ligand of interestN
Has protein modificationY

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Experimental details

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Experiment

ExperimentMethod: ELECTRON MICROSCOPY
EM experimentAggregation state: PARTICLE / 3D reconstruction method: single particle reconstruction

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Sample preparation

ComponentName: Complex of Qb-Ab4 / Type: COMPLEX / Entity ID: all / Source: RECOMBINANT
Source (natural)Organism: Mus (mice)
Source (recombinant)Organism: Homo sapiens (human)
Buffer solutionpH: 7.4
SpecimenEmbedding applied: NO / Shadowing applied: NO / Staining applied: NO / Vitrification applied: YES
VitrificationCryogen name: ETHANE

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Electron microscopy imaging

Experimental equipment
Model: Titan Krios / Image courtesy: FEI Company
MicroscopyModel: FEI TITAN KRIOS
Electron gunElectron source: FIELD EMISSION GUN / Accelerating voltage: 300 kV / Illumination mode: FLOOD BEAM
Electron lensMode: BRIGHT FIELD / Nominal defocus max: 1500 nm / Nominal defocus min: 1000 nm
Image recordingElectron dose: 60 e/Å2 / Film or detector model: GATAN K2 SUMMIT (4k x 4k)

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Processing

EM softwareName: PHENIX / Version: 1.13_2998: / Category: model refinement
CTF correctionType: PHASE FLIPPING AND AMPLITUDE CORRECTION
3D reconstructionResolution: 3.8 Å / Resolution method: FSC 0.143 CUT-OFF / Num. of particles: 123614 / Symmetry type: POINT

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