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Streptococcal M1 protein constructs a pathological host fibrinogen network

Pauline Macheboeuf1, Cosmo Buffalo, Chi-yu Fu

  • 1Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093, USA.

Nature
|April 9, 2011
PubMed

Insights

Streptococcus M1 protein forms a unique complex with fibrinogen, activating neutrophils and causing toxic shock-like symptoms. Understanding this structure reveals how the bacteria cause severe tissue injury.

Area of Science:

  • Microbiology
  • Structural Biology
  • Immunology

Background:

  • Group A Streptococcus (GAS) is a leading cause of invasive infections.
  • M1 protein is a major GAS virulence factor responsible for toxic-shock-like symptoms.
  • Neutrophil activation is critical in the pathogenesis of streptococcal toxic shock.

Purpose of the Study:

  • To provide a structural explanation for the pathological properties of the M1-fibrinogen complex.
  • To elucidate the mechanism of M1-induced neutrophil activation.
  • To understand the structural basis of streptococcal toxic shock.

Main Methods:

  • X-ray crystallography to determine the structure of the M1-fibrinogen complex.
  • Biochemical assays to assess neutrophil activation.
  • Analysis of supramolecular network formation.

Main Results:

  • The M1 protein dimer organizes four fibrinogen molecules into a cross-like pattern.
  • This specific supramolecular network is essential for neutrophil activation.
  • Disruption of this network prevents pathological outcomes.
  • The network is distinct from a typical fibrin clot.

Conclusions:

  • The unique structure of the M1-fibrinogen complex explains its role in inducing vascular leakage and tissue injury.
  • Neutrophil activation is mediated by a specific supramolecular network formed by the complex.
  • These findings offer insights into the pathophysiology of streptococcal toxic shock.

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