3HVD

The Protective Antigen Component of Anthrax Toxin Forms Functional Octameric Complexes

Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 3.21 Å
  • R-Value Free: 0.249 
  • R-Value Work: 0.210 
  • R-Value Observed: 0.212 

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This is version 1.3 of the entry. See complete history. 


Literature

The protective antigen component of anthrax toxin forms functional octameric complexes.

Kintzer, A.F., Thoren, K.L., Sterling, H.J., Dong, K.C., Feld, G.K., Tang, I.I., Zhang, T.T., Williams, E.R., Berger, J.M., Krantz, B.A.

(2009) J Mol Biol 392: 614-629

  • DOI: https://doi.org/10.1016/j.jmb.2009.07.037
  • Primary Citation of Related Structures:  
    3HVD

  • PubMed Abstract: 

    • The assembly of bacterial toxins and virulence factors is critical to their function, but the regulation of assembly during infection has not been studied. We begin to address this question using anthrax toxin as a model. The protective antigen (PA) component of the toxin assembles into ring-shaped homooligomers that bind the two other enzyme components of the toxin, lethal factor (LF) and edema factor (EF), to form toxic complexes ...

    The assembly of bacterial toxins and virulence factors is critical to their function, but the regulation of assembly during infection has not been studied. We begin to address this question using anthrax toxin as a model. The protective antigen (PA) component of the toxin assembles into ring-shaped homooligomers that bind the two other enzyme components of the toxin, lethal factor (LF) and edema factor (EF), to form toxic complexes. To disrupt the host, these toxic complexes are endocytosed, such that the PA oligomer forms a membrane-spanning channel that LF and EF translocate through to enter the cytosol. Using single-channel electrophysiology, we show that PA channels contain two populations of conductance states, which correspond to two different PA pre-channel oligomers observed by electron microscopy-the well-described heptamer and a novel octamer. Mass spectrometry demonstrates that the PA octamer binds four LFs, and assembly routes leading to the octamer are populated with even-numbered, dimeric and tetrameric, PA intermediates. Both heptameric and octameric PA complexes can translocate LF and EF with similar rates and efficiencies. Here, we report a 3.2-A crystal structure of the PA octamer. The octamer comprises approximately 20-30% of the oligomers on cells, but outside of the cell, the octamer is more stable than the heptamer under physiological pH. Thus, the PA octamer is a physiological, stable, and active assembly state capable of forming lethal toxins that may withstand the hostile conditions encountered in the bloodstream. This assembly mechanism may provide a novel means to control cytotoxicity.

    Organizational Affiliation: 

    Department of Chemistry, University of California, Berkeley, 94720, USA.



Macromolecules
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(by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
Protective antigen
A, B, C, D, E, F, G, H
A, B, C, D, E, F, G, H
548Bacillus anthracisMutation(s): 2 
Gene Names: pa, PAG
UniProt
Find proteins for Q08G54 (Bacillus anthracis)
Explore Q08G54 
Go to UniProtKB:  Q08G54
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ08G54
Protein Feature View
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 3.21 Å
  • R-Value Free: 0.249 
  • R-Value Work: 0.210 
  • R-Value Observed: 0.212 
  • Space Group: P 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 125.602α = 106.64
b = 125.67β = 110.82
c = 125.823γ = 110.98
Software Package:
Software NamePurpose
ADSCdata collection
PHASERphasing
PHENIXrefinement
HKL-2000data reduction
HKL-2000data scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2009-08-25
    Type: Initial release
  • Version 1.1: 2011-07-13
    Changes: Version format compliance
  • Version 1.2: 2017-08-16
    Changes: Refinement description, Source and taxonomy
  • Version 1.3: 2021-10-13
    Changes: Database references, Derived calculations