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pH-induced conformational changes in Clostridium difficile toxin B.

M Qa'Dan1, L M Spyres, J D Ballard

  • 1Department of Botany and Microbiology, The University of Oklahoma, Norman, Oklahoma 73019, USA.

Infection and Immunity
|April 18, 2000
PubMed
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Acidic pH triggers structural changes in Clostridium difficile Toxin B, affecting its cytosolic entry. This pH-induced hydrophobicity is reversible and impacts toxin activity, offering insights into its cellular mechanisms.

Area of Science:

  • Microbiology
  • Cell Biology
  • Toxicology

Background:

  • Clostridium difficile Toxin B is a key virulence factor.
  • It functions as a monoglucosylating toxin targeting intracellular host proteins.
  • Understanding toxin entry and structural dynamics is crucial for therapeutic development.

Purpose of the Study:

  • To investigate the influence of acidic pH on Clostridium difficile Toxin B's cytosolic entry.
  • To characterize pH-induced structural modifications in Toxin B.
  • To explore the reversibility of these structural changes and their functional implications.

Main Methods:

  • Utilized bafilomycin A1 to inhibit endosomal acidification and toxin translocation.
  • Manipulated extracellular pH to assess its effect on toxin entry and cellular damage.

Related Experiment Videos

  • Employed fluorescent probes (TNS) and intrinsic tryptophan fluorescence to monitor structural changes.
  • Assessed protease susceptibility (Staphylococcus aureus V8 protease) at different pH levels.

    • Main Results:

    • Bafilomycin A1 effectively blocked cytopathic effects of Toxin B.
    • Low extracellular pH bypassed bafilomycin A1 inhibition, facilitating toxin entry.
    • Acidic pH induced increased hydrophobicity and altered tryptophan fluorescence in Toxin B.
    • These pH-induced structural changes were reversible upon returning to neutral pH.
    • Toxin B exhibited altered protease susceptibility at acidic pH.

    Conclusions:

    • Acidic pH significantly impacts Clostridium difficile Toxin B's structure and cellular translocation.
    • The observed changes in hydrophobicity and conformation are reversible.
    • These findings provide insights into the mechanism of Toxin B entry into mammalian cells.