Crystal Structure of A3VP1 of AgI/II of Streptococcus mutans

Experimental Data Snapshot

  • Resolution: 1.80 Å
  • R-Value Free: 0.228 
  • R-Value Work: 0.190 
  • R-Value Observed: 0.190 

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Elongated fibrillar structure of a streptococcal adhesin assembled by the high-affinity association of alpha- and PPII-helices.

Larson, M.R.Rajashankar, K.R.Patel, M.H.Robinette, R.A.Crowley, P.J.Michalek, S.Brady, L.J.Deivanayagam, C.

(2010) Proc Natl Acad Sci U S A 107: 5983-5988

  • DOI: https://doi.org/10.1073/pnas.0912293107
  • Primary Citation of Related Structures:  
    3IOX, 3IPK

  • PubMed Abstract: 

    Streptococcus mutans antigen I/II (AgI/II) is a cell surface-localized protein adhesin that interacts with salivary components within the salivary pellicle. AgI/II contributes to virulence and has been studied as an immunological and structural target, but a fundamental understanding of its underlying architecture has been lacking. Here we report a high-resolution (1.8 A) crystal structure of the A(3)VP(1) fragment of S. mutans AgI/II that demonstrates a unique fibrillar form (155 A) through the interaction of two noncontiguous regions in the primary sequence. The A(3) repeat of the alanine-rich domain adopts an extended alpha-helix that intertwines with the P(1) repeat polyproline type II (PPII) helix to form a highly extended stalk-like structure heretofore unseen in prokaryotic or eukaryotic protein structures. Velocity sedimentation studies indicate that full-length AgI/II that contains three A/P repeats extends over 50 nanometers in length. Isothermal titration calorimetry revealed that the high-affinity association between the A(3) and P(1) helices is enthalpically driven. Two distinct binding sites on AgI/II to the host receptor salivary agglutinin (SAG) were identified by surface plasmon resonance (SPR). The current crystal structure reveals that AgI/II family proteins are extended fibrillar structures with the number of alanine- and proline-rich repeats determining their length.

  • Organizational Affiliation

    Department of Physiology and Biophysics, University of Alabama, Birmingham, AL 35294, USA.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
AgI/II497Streptococcus mutansMutation(s): 0 
Gene Names: pa
Find proteins for A8R5D9 (Streptococcus mutans)
Explore A8R5D9 
Go to UniProtKB:  A8R5D9
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupA8R5D9
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.80 Å
  • R-Value Free: 0.228 
  • R-Value Work: 0.190 
  • R-Value Observed: 0.190 
  • Space Group: P 21 21 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 70.725α = 90
b = 153.057β = 90
c = 49.677γ = 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: 2010-04-14
    Type: Initial release
  • Version 1.1: 2011-07-13
    Changes: Version format compliance
  • Version 1.2: 2023-09-06
    Changes: Data collection, Database references, Derived calculations, Refinement description