An arm-swapped dimer of the S. pyogenes pilin specific assembly factor SipA

Experimental Data Snapshot

  • Resolution: 1.67 Å
  • R-Value Free: 0.215 
  • R-Value Work: 0.185 
  • R-Value Observed: 0.187 

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An arm-swapped dimer of the Streptococcus pyogenes pilin specific assembly factor SipA.

Young, P.G.Kang, H.J.Baker, E.N.

(2013) J Struct Biol 183: 99-104

  • DOI: https://doi.org/10.1016/j.jsb.2013.05.021
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    Streptococcus pyogenes (group A streptococcus [GAS]) is a major human pathogen. Attachment of GAS to host cells depends in large part on pili. These assemblies are built from multiple covalently linked subunits of a backbone protein (FctA), which forms the shaft of the pilus, and two minor pilin proteins, FctB anchoring the pilus to the cell wall and Cpa functioning as the adhesin at the tip. Polymerisation of the pilin subunits is mediated by a specific sortase, which catalyzes the formation of peptide bonds linking successive subunits. An additional gene, SipA, is also essential for GAS pilus polymerisation, but its function remains undefined. Here we report the crystal structure of a truncated SipA protein from GAS, determined at 1.67Å resolution. The structure reveals that SipA has the same core fold as the Escherichia coli type-I signal peptidase (SPase-I), but has a much smaller non-catalytic domain. The truncated protein, which lacks 9 N-terminal residues, forms an arm-swapped dimer in which the C-terminal β-strand of each monomer crosses over to interact with an N-terminal strand from the other monomer. In addition, there is no peptide binding cleft and significant differences in the putative membrane association region.

  • Organizational Affiliation

    School of Biological Sciences, University of Auckland, Auckland, New Zealand. p.young@auckland.ac.nz

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
LepA129Streptococcus pyogenesMutation(s): 0 
Gene Names: lepAsipA
Find proteins for Q8RP52 (Streptococcus pyogenes)
Explore Q8RP52 
Go to UniProtKB:  Q8RP52
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ8RP52
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.67 Å
  • R-Value Free: 0.215 
  • R-Value Work: 0.185 
  • R-Value Observed: 0.187 
  • Space Group: P 41 21 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 53.285α = 90
b = 53.285β = 90
c = 131.749γ = 90
Software Package:
Software NamePurpose
MAR345dtbdata collection
XDSdata reduction
SCALAdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2013-06-26
    Type: Initial release
  • Version 1.1: 2013-07-24
    Changes: Database references
  • Version 1.2: 2024-02-28
    Changes: Data collection, Database references, Derived calculations