Structural insight into the giant calcium-binding adhesin SiiE: implications for the adhesion of Salmonella enterica to polarized epithelial cells

Experimental Data Snapshot

  • Resolution: 1.85 Å
  • R-Value Free: 0.246 
  • R-Value Work: 0.206 
  • R-Value Observed: 0.209 

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Structural Insight Into the Giant Ca(2+)-Binding Adhesin Siie: Implications for the Adhesion of Salmonella Enterica to Polarized Epithelial Cells.

Griessl, M.H.Schmid, B.Kassler, K.Braunsmann, C.Ritter, R.Barlag, B.Stierhof, Y.Sturm, K.U.Danzer, C.Wagner, C.Schaffer, T.E.Sticht, H.Hensel, M.Muller, Y.A.

(2013) Structure 21: 741

  • DOI: https://doi.org/10.1016/j.str.2013.02.020
  • Primary Citation of Related Structures:  
    2YN3, 2YN5

  • PubMed Abstract: 

    SiiE from Salmonella enterica is a giant 5,559-residue-long nonfimbrial adhesin that is secreted by a type 1 secretion system (T1SS) and initiates bacterial adhesion to polarized host cells. Structural insight has been gained into the 53 bacterial Ig-like (BIg) domains of SiiE, which account for 94% of the entire SiiE sequence. The crystal structure of a fragment comprising BIg domains 50 to 52 of SiiE reveals the BIg domain architecture and highlights two types of SiiE-specific Ca²⁺-binding sites. Sequence homology considerations suggest that full-length SiiE interacts with more than 100 Ca²⁺ ions. Molecular dynamics simulations and single-molecule imaging indicate that Ca²⁺ binding confers SiiE with a rigid 200 nm rod-like habitus that is required to reach out beyond the Salmonella lipopolysaccharide layer and to promote adhesion to host cells. The crystal structure suggests plausible routes for the establishment of the initial contact between Salmonella and host cells.

  • Organizational Affiliation

    Lehrstuhl für Biotechnik, Department of Biology, Friedrich-Alexander-University of Erlangen-Nuremberg, 91054 Erlangen, Germany.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
A, B
288Salmonella enterica subsp. enterica serovar Typhimurium str. LT2Mutation(s): 0 
Find proteins for Q8ZKG6 (Salmonella typhimurium (strain LT2 / SGSC1412 / ATCC 700720))
Explore Q8ZKG6 
Go to UniProtKB:  Q8ZKG6
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ8ZKG6
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.85 Å
  • R-Value Free: 0.246 
  • R-Value Work: 0.206 
  • R-Value Observed: 0.209 
  • Space Group: C 1 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 129.4α = 90
b = 69.04β = 90.92
c = 67.26γ = 90
Software Package:
Software NamePurpose
XDSdata reduction
XSCALEdata scaling

Structure Validation

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Entry History 

Revision History  (Full details and data files)

  • Version 1.0: 2013-04-03
    Type: Initial release
  • Version 1.1: 2013-06-05
    Changes: Database references
  • Version 1.2: 2023-12-20
    Changes: Data collection, Database references, Derived calculations, Other, Refinement description