The crystal structure of vaccinia virus A26 (residues 1-397)

Experimental Data Snapshot

  • Resolution: 1.18 Å
  • R-Value Free: 0.130 
  • R-Value Work: 0.107 
  • R-Value Observed: 0.108 

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Vaccinia viral A26 protein is a fusion suppressor of mature virus and triggers membrane fusion through conformational change at low pH.

Chang, H.W.Yang, C.H.Luo, Y.C.Su, B.G.Cheng, H.Y.Tung, S.Y.Carillo, K.J.D.Liao, Y.T.Tzou, D.M.Wang, H.C.Chang, W.

(2019) PLoS Pathog 15: e1007826-e1007826

  • DOI: https://doi.org/10.1371/journal.ppat.1007826
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    Vaccinia mature virus requires A26 envelope protein to mediate acid-dependent endocytosis into HeLa cells in which we hypothesized that A26 protein functions as an acid-sensitive membrane fusion suppressor. Here, we provide evidence showing that N-terminal domain (aa1-75) of A26 protein is an acid-sensitive region that regulates membrane fusion. Crystal structure of A26 protein revealed that His48 and His53 are in close contact with Lys47, Arg57, His314 and Arg312, suggesting that at low pH these His-cation pairs could initiate conformational changes through protonation of His48 and His53 and subsequent electrostatic repulsion. All the A26 mutant mature viruses that interrupted His-cation pair interactions of His48 and His 53 indeed have lost virion infectivity. Isolation of revertant viruses revealed that second site mutations caused frame shifts and premature termination of A26 protein such that reverent viruses regained cell entry through plasma membrane fusion. Together, we conclude that viral A26 protein functions as an acid-sensitive fusion suppressor during vaccinia mature virus endocytosis.

  • Organizational Affiliation

    Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Protein A26397Vaccinia virus WRMutation(s): 0 
Gene Names: VACWR149A26L
Find proteins for P24758 (Vaccinia virus (strain Western Reserve))
Explore P24758 
Go to UniProtKB:  P24758
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP24758
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.18 Å
  • R-Value Free: 0.130 
  • R-Value Work: 0.107 
  • R-Value Observed: 0.108 
  • Space Group: P 1 21 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 45.38α = 90
b = 80.718β = 113.8
c = 53.812γ = 90
Software Package:
Software NamePurpose
BUCCANEERmodel building
HKL-2000data scaling
HKL-2000data reduction

Structure Validation

View Full Validation Report

Entry History & Funding Information

Deposition Data

Funding OrganizationLocationGrant Number
Ministry of Science and Technology (Taiwan)Taiwan106-2321-B-001 -033
Ministry of Science and Technology (Taiwan)Taiwan106-2311-B-038 -002

Revision History  (Full details and data files)

  • Version 1.0: 2019-06-12
    Type: Initial release
  • Version 1.1: 2019-07-10
    Changes: Data collection, Database references