Crystal Structure of Anthrax Protective Antigen (Membrane Insertion Loop Deleted) to 1.45-A resolution

Experimental Data Snapshot

  • Resolution: 1.45 Å
  • R-Value Free: 0.216 
  • R-Value Work: 0.194 
  • R-Value Observed: 0.194 

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Domain flexibility modulates the heterogeneous assembly mechanism of anthrax toxin protective antigen.

Feld, G.K.Kintzer, A.F.Tang, I.I.Thoren, K.L.Krantz, B.A.

(2012) J Mol Biol 415: 159-174

  • DOI: https://doi.org/10.1016/j.jmb.2011.10.035
  • Primary Citation of Related Structures:  
    3TEW, 3TEX, 3TEY, 3TEZ

  • PubMed Abstract: 

    The three protein components of anthrax toxin are nontoxic individually, but they form active holotoxin complexes upon assembly. The role of the protective antigen (PA) component of the toxin is to deliver two other enzyme components, lethal factor and edema factor, across the plasma membrane and into the cytoplasm of target cells. PA is produced as a proprotein, which must be proteolytically activated; generally, cell surface activation is mediated by a furin family protease. Activated PA can then assemble into one of two noninterconverting oligomers, a homoheptamer and a homooctamer, which have unique properties. Herein we describe molecular determinants that influence the stoichiometry of PA in toxin complexes. By tethering PA domain 4 (D4) to domain 2 with two different-length cross-links, we can control the relative proportions of PA heptamers and octamers. The longer cross-link favors octamer formation, whereas the shorter one favors formation of the heptamer. X-ray crystal structures of PA (up to 1.45 Å resolution), including these cross-linked PA constructs, reveal that a hinge-like movement of D4 correlates with the relative preference for each oligomeric architecture. Furthermore, we report the conformation of the flexible loop containing the furin cleavage site and show that, for efficient processing, the furin site cannot be moved ~5 or 6 residues within the loop. We propose that there are different orientations of D4 relative to the main body of PA that favor the formation of either the heptamer or the octamer.

  • Organizational Affiliation

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

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Protective antigen715Bacillus anthracisMutation(s): 0 
Gene Names: BXA0164GBAA_pXO1_0164pagpagAPX01pXO1-110
Find proteins for P13423 (Bacillus anthracis)
Explore P13423 
Go to UniProtKB:  P13423
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP13423
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.45 Å
  • R-Value Free: 0.216 
  • R-Value Work: 0.194 
  • R-Value Observed: 0.194 
  • Space Group: P 21 21 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 71.355α = 90
b = 93.385β = 90
c = 118.078γ = 90
Software Package:
Software NamePurpose
HKL-2000data collection
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: 2011-10-26
    Type: Initial release
  • Version 1.1: 2012-05-23
    Changes: Database references
  • Version 1.2: 2023-09-13
    Changes: Data collection, Database references, Derived calculations, Refinement description