3.65 Angstrom Crystal Structure of Serine-rich Repeat Protein (Srr2) from Streptococcus agalactiae

Experimental Data Snapshot

  • Resolution: 3.65 Å
  • R-Value Free: 0.241 
  • R-Value Work: 0.213 
  • R-Value Observed: 0.215 

Starting Model: experimental
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Characterization of Fibrinogen Binding by Glycoproteins Srr1 and Srr2 of Streptococcus agalactiae.

Seo, H.S.Minasov, G.Seepersaud, R.Doran, K.S.Dubrovska, I.Shuvalova, L.Anderson, W.F.Iverson, T.M.Sullam, P.M.

(2013) J Biol Chem 288: 35982-35996

  • DOI: https://doi.org/10.1074/jbc.M113.513358
  • Primary Citation of Related Structures:  
    4MBO, 4MBR

  • PubMed Abstract: 

    The serine-rich repeat glycoproteins of Gram-positive bacteria comprise a large family of cell wall proteins. Streptococcus agalactiae (group B streptococcus, GBS) expresses either Srr1 or Srr2 on its surface, depending on the strain. Srr1 has recently been shown to bind fibrinogen, and this interaction contributes to the pathogenesis of GBS meningitis. Although strains expressing Srr2 appear to be hypervirulent, no ligand for this adhesin has been described. We now demonstrate that Srr2 also binds human fibrinogen and that this interaction promotes GBS attachment to endothelial cells. Recombinant Srr1 and Srr2 bound fibrinogen in vitro, with affinities of KD = 2.1 × 10(-5) and 3.7 × 10(-6) M, respectively, as measured by surface plasmon resonance spectroscopy. The binding site for Srr1 and Srr2 was localized to tandem repeats 6-8 of the fibrinogen Aα chain. The structures of both the Srr1 and Srr2 binding regions were determined and, in combination with mutagenesis studies, suggest that both Srr1 and Srr2 interact with a segment of these repeats via a "dock, lock, and latch" mechanism. Moreover, properties of the latch region may account for the increased affinity between Srr2 and fibrinogen. Together, these studies identify how greater affinity of Srr2 for fibrinogen may contribute to the increased virulence associated with Srr2-expressing strains.

  • Organizational Affiliation

    From the Division of Infectious Diseases, Veterans Affairs Medical Center, University of California at San Francisco and the Northern California Institute for Research and Education, San Francisco, California 94121.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Serine-rich repeat protein 2344Streptococcus agalactiaeMutation(s): 0 
Find proteins for Q49RA6 (Streptococcus agalactiae)
Explore Q49RA6 
Go to UniProtKB:  Q49RA6
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ49RA6
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

Unit Cell:
Length ( Å )Angle ( ˚ )
a = 97.598α = 90
b = 97.598β = 90
c = 173.269γ = 90
Software Package:
Software NamePurpose
Blu-Icedata collection
HKL-3000data reduction
HKL-3000data scaling

Structure Validation

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Entry History 

Revision History  (Full details and data files)

  • Version 1.0: 2013-11-06
    Type: Initial release
  • Version 1.1: 2013-11-13
    Changes: Database references
  • Version 1.2: 2014-01-01
    Changes: Database references
  • Version 1.3: 2017-11-15
    Changes: Refinement description
  • Version 1.4: 2023-09-20
    Changes: Data collection, Database references, Refinement description