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In Vitro Assay of Bacterial Adhesion onto Mammalian Epithelial Cells
05:57

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Published on: May 16, 2011

Characterization of emb, a gene encoding the major adhesin of Streptococcus defectivus

R Manganelli1, I van de Rijn

  • 1Department of Microbiology and Immunology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA.

Infection and Immunity
|December 24, 1998
PubMed

Insights

Streptococcus defectivus possesses a large surface protein, Emb, responsible for binding to the extracellular matrix. This protein, encoded by the emb gene, may represent a new family of streptococcal fibrillar proteins.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Protein Science

Background:

  • Streptococcus defectivus belongs to nutritionally variant streptococci (NVS), linked to endocarditis and otitis media.
  • Previous research indicated NVS-47, an S. defectivus isolate, binds to the extracellular matrix via a high-molecular-weight surface protein.

Purpose of the Study:

  • To identify and characterize the gene encoding the extracellular matrix-binding protein in S. defectivus.
  • To elucidate the structure and function of this novel surface protein.

Main Methods:

  • Transposon mutagenesis was employed to identify the relevant gene.
  • Partial gene sequencing of the identified gene (emb) was performed.
  • Bioinformatic analysis predicted protein structure and identified functional domains.

Main Results:

  • The gene emb, encoding a protein over 14 kb, was identified.
  • The Emb protein contains at least 50 repeats of 77 amino acids, predicted to form a coiled-coil structure.
  • Extracellular matrix binding activity was localized to the N-terminal domain of the Emb protein.

Conclusions:

  • Emb is a novel, large, fibrillar surface protein of Streptococcus defectivus.
  • The N-terminus of Emb mediates extracellular matrix binding.
  • Emb is proposed as the prototype for a new family of streptococcal fibrillar proteins.

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