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Crystal structure of PfbA, a surface adhesin of Streptococcus pneumoniae, provides hints into its interaction with

D S Jemima Beulin1, Masaya Yamaguchi2, Shigetada Kawabata3

  • 1Centre of Advanced Study in Crystallography and Biophysics, University of Madras, Guindy Campus, Chennai 600 025, India.

International Journal of Biological Macromolecules
|December 11, 2013
PubMed

Insights

Streptococcus pneumoniae adhesin PfbA binds host fibronectin and plasminogen. Its crystal structure reveals a beta helix and a disordered region potentially mediating fibronectin binding, crucial for pathogenesis.

Area of Science:

  • Microbiology
  • Structural Biology
  • Molecular Pathogenesis

Background:

  • PfbA is a key surface adhesin and invasin of Streptococcus pneumoniae, contributing to pathogenesis by binding host extracellular matrix components.
  • It interacts with human fibronectin and plasminogen, both crucial for bacterial invasion and survival within the host.
  • Understanding PfbA's structure is vital for developing targeted therapeutic strategies against pneumococcal infections.

Purpose of the Study:

  • To determine the crystal structure of a specific fragment of PfbA (PfbA150-607) from Streptococcus pneumoniae strain R6.
  • To elucidate the structural basis for PfbA's interactions with fibronectin and plasminogen.
  • To compare the structural features of PfbA with known adhesins from other bacterial species.

Main Methods:

  • Recombinant PfbA150-607 protein was expressed and purified.
  • The crystal structure was determined using the multiwavelength anomalous dispersion (MAD) method.
  • The structure was refined to a resolution of 1.90 Å.

Main Results:

  • The crystal structure of rPfbA150-607 revealed a rigid parallel beta helix (residues Thr150 to Lys570) followed by a short disordered region (residues 571-607) containing beta hairpins.
  • The beta helix shares structural similarities with polysaccharide-modifying enzymes.
  • Structural and sequence analysis indicated that the disordered region likely mediates fibronectin binding, similar to other characterized fibronectin-binding proteins.
  • A high number of surface-exposed lysines in PfbA150-607 suggest their involvement in plasmin(ogen) binding.

Conclusions:

  • The determined structure of PfbA150-607 provides insights into the molecular mechanisms of Streptococcus pneumoniae adhesion and invasion.
  • The disordered C-terminal region is predicted to be the primary fibronectin-binding site.
  • Surface-exposed lysines are likely involved in plasminogen binding, further highlighting PfbA's role as a multifunctional adhesin.
Keywords:
Crystal structureFibronectin-bindingPfbAS. pneumoniaeSurface adhesin

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