4N31

Structure and activity of Streptococcus pyogenes SipA: a signal peptidase homologue essential for pilus polymerisation


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.20 Å
  • R-Value Free: 0.229 
  • R-Value Work: 0.201 
  • R-Value Observed: 0.202 

Starting Model: experimental
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Ligand Structure Quality Assessment 


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Literature

Structure and activity of Streptococcus pyogenes SipA: a signal peptidase-like protein essential for pilus polymerisation.

Young, P.G.Proft, T.Harris, P.W.Brimble, M.A.Baker, E.N.

(2014) PLoS One 9: e99135-e99135

  • DOI: https://doi.org/10.1371/journal.pone.0099135
  • Primary Citation of Related Structures:  
    4N31

  • PubMed Abstract: 

    The pili expressed on the surface of the human pathogen Streptococcus pyogenes play an important role in host cell attachment, colonisation and pathogenesis. These pili are built from two or three components, an adhesin subunit at the tip, a major pilin that forms a polymeric shaft, and a basal pilin that is attached to the cell wall. Assembly is carried out by specific sortase (cysteine transpeptidase) enzyme. These components are encoded in a small gene cluster within the S. pyogenes genome, often together with another protein, SipA, whose function is unknown. We show through functional assays, carried out by expressing the S. pyogenes pilus components in Lactococcus lactis, SipA from the clinically important M1T1 strain is essential for pilus assembly, and that SipA function is likely to be conserved in all S. pyogenes. From the crystal structure of SipA we confirm that SipA belongs to the family of bacterial signal peptidases (SPases), which process the signal-peptides of secreted proteins. In contrast to a previous arm-swapped SipA dimer, this present structure shows that its principal domain closely resembles the catalytic domain of SPases and has a very similar peptide-binding cleft, but it lacks the catalytic Ser and Lys residues characteristic of SPases. In SipA these are replaced by Asp and Gly residues, which play no part in activity. We propose that SipA functions by binding a key component at the bacterial cell surface, in a conformation that facilitates pilus assembly.


  • Organizational Affiliation

    School of Biological Sciences, University of Auckland, Auckland, New Zealand.


Macromolecules
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
SipA
A, B
163Streptococcus pyogenesMutation(s): 0 
Gene Names: sipA
EC: 3.4.21.89
UniProt
Find proteins for R9TES9 (Streptococcus pyogenes)
Explore R9TES9 
Go to UniProtKB:  R9TES9
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupR9TES9
Sequence Annotations
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.20 Å
  • R-Value Free: 0.229 
  • R-Value Work: 0.201 
  • R-Value Observed: 0.202 
  • Space Group: P 64 2 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 132.811α = 90
b = 132.811β = 90
c = 107.156γ = 120
Software Package:
Software NamePurpose
ADSCdata collection
PHASERphasing
REFMACrefinement
XDSdata reduction
SCALAdata scaling

Structure Validation

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Ligand Structure Quality Assessment 


Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2014-08-20
    Type: Initial release
  • Version 1.1: 2023-09-20
    Changes: Data collection, Database references, Derived calculations, Refinement description