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Cell surface proteins of a group A streptococcus type M4: the IgA receptor and a receptor related to M proteins are

G Lindahl1

  • 1Department of Medical Microbiology, University of Lund, Sweden.

Molecular & General Genetics : MGG
|April 1, 1989
PubMed

Insights

Researchers cloned two genes from group A streptococcus, encoding IgA and fibrinogen binding proteins. These cell surface proteins, Arp4 and an M protein, are closely linked and may be coordinately regulated, as indicated by bacterial mutants lacking both.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Immunology

Background:

  • Group A Streptococcus (GAS) possesses diverse cell surface proteins crucial for pathogenesis.
  • Understanding these proteins aids in developing strategies against GAS infections.
  • Specific GAS strains, like M4, express unique surface proteins with potential pathogenic roles.

Purpose of the Study:

  • To clone and characterize genes encoding cell surface proteins in group A Streptococcus type M4.
  • To investigate the relationship and regulation of IgA binding protein (Arp4) and fibrinogen binding protein (M protein) genes.
  • To develop a method for isolating bacterial mutants lacking both surface proteins.

Main Methods:

  • Gene cloning and expression in Escherichia coli.
  • Protein purification and partial characterization.
  • Immunological cross-reactivity assays.
  • Analysis of bacterial mutants and genetic linkage.

Main Results:

  • Two genes for cell surface proteins, IgA binding and fibrinogen binding, were successfully cloned from GAS M4.
  • Both proteins were purified and characterized; Arp4 showed similarity but not identity to other IgA receptors.
  • The genes are closely linked, and mutants lacking both proteins were identified, suggesting coordinate regulation.
  • Evidence indicates the fibrinogen binding protein is a streptococcal M protein.

Conclusions:

  • The study identified and characterized two novel cell surface proteins in GAS M4, Arp4 and a fibrinogen binding M protein.
  • The close linkage and coordinate regulation of these genes offer insights into GAS surface protein expression.
  • The findings contribute to understanding GAS virulence factors and potential therapeutic targets.

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