NMR structure of a fungal virulence factor reveals structural homology with mammalian saposin B

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Moriah R Beck1, Gregory T Dekoster, David P Cistola

  • 1Department of Molecular Microbiology, Washington University in St Louis, St Louis, MO, USA.

Molecular Microbiology
|March 21, 2009
PubMed

Insights

The fungal virulence factor CBP, a calcium binding protein, has an unknown mechanism. Its NMR structure reveals a saposin fold, suggesting it binds lipids and interacts with host cells.

Area of Science:

  • Molecular biology
  • Mycology
  • Structural biology

Background:

  • The fungal protein CBP is a known virulence factor in Histoplasma capsulatum.
  • Its mechanism of virulence is currently unknown.
  • CBP was identified by its calcium-binding ability and abundance in secreted fungal proteins.

Purpose of the Study:

  • To determine the atomic-level structure of the fungal virulence factor CBP.
  • To elucidate the potential mechanism of virulence for CBP.

Main Methods:

  • Nuclear Magnetic Resonance (NMR) spectroscopy was used to determine the structure of CBP.
  • Structural homology analysis was performed to infer protein function.

Main Results:

  • The NMR structure revealed CBP as a highly intertwined homodimer.
  • Each monomer adopts a saposin fold, a characteristic of lipid-binding proteins.
  • This represents the first atomic-level NMR model of any fungal virulence factor.

Conclusions:

  • The saposin fold suggests CBP functions as a lipid-binding protein.
  • CBP may interact with host cell lipids, specifically glycolipids in the phagolysosome.
  • This structural insight provides a basis for understanding CBP's role in fungal virulence.

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