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Related Experiment Videos

Characterisation of opacity factor from group-A streptococci.

G A Saravani1, D R Martin

  • 1New Zealand Communicable Disease Centre, Porirua.

Journal of Medical Microbiology
|September 1, 1990
PubMed
Summary

Extracellular opacity factor (OF) from Streptococcus M-type 22 was purified and characterized. The study suggests OF is an aspartic proteinase, crucial for understanding bacterial virulence.

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Area of Science:

  • Microbiology
  • Biochemistry

Background:

  • Group A Streptococcus (GAS) produces virulence factors like opacity factor (OF).
  • Understanding the enzymatic nature of OF is key to elucidating GAS pathogenesis.

Purpose of the Study:

  • To purify and characterize the extracellular opacity factor (OF) from Group A Streptococcus M-type 22.
  • To determine the enzymatic class of the purified OF.

Main Methods:

  • Purification using ammonium sulphate precipitation, ion-exchange chromatography (DE-52 cellulose), and gel filtration (Sephacryl S-400).
  • Characterization by SDS-PAGE, antiserum inhibition assays, and enzyme activity assays across varying pH and temperature.
  • Inhibition studies using specific protease inhibitors.

Main Results:

  • Purified OF was heterogeneous and eluted near the void volume.
  • Antiserum against OF inhibited all preparations, and no M protein was detected.
  • Optimal OF activity was observed at pH 6, with inactivation at high temperatures.
  • Pepstatin A inhibited OF activity, while other protease inhibitors had no effect, indicating aspartic proteinase activity.

Conclusions:

  • Extracellular opacity factor (OF) from Group A Streptococcus M-type 22 is an aspartic proteinase.
  • This finding provides insights into the biochemical properties and potential role of OF in bacterial infections.

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