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Reduced pH causes structural changes in the potent mitogenic toxin of Pasteurella multocida
M G Smyth1, I G Sumner, A J Lax
1Institute of Food Research, Whiteknights Road, Reading, Berkshire, UK.
FEMS Microbiology Letters
|November 5, 1999
Summary
Pasteurella multocida toxin undergoes structural changes at acidic pH, affecting its unfolding. The toxin refolds effectively, suggesting a distinct domain structure.
Area of Science:
- Biochemistry
- Molecular Biology
- Microbial Pathogenesis
Background:
- Pasteurella multocida toxin is a mitogen with suspected intracellular activity.
- Understanding toxin structure is key to elucidating its mechanism of action.
Purpose of the Study:
- To investigate the structural stability and conformational changes of Pasteurella multocida toxin under varying pH conditions.
- To explore the refolding capacity and potential domain structure of the toxin.
Main Methods:
- Transverse urea gradient gel electrophoresis at pH 8.0 and 6.1.
- Circular dichroism spectroscopy.
- Urea-induced denaturation and refolding experiments.
Main Results:
- A single major unfolding transition was observed at 4 M urea at pH 8.0.
- The unfolding transition shifted to 3.5 M urea at pH 6.1, indicating pH-dependent stability.
- Circular dichroism confirmed structural changes at acidic pH.
- The toxin demonstrated high recovery of biological activity after denaturation and refolding from 8 M urea.
Conclusions:
- Pasteurella multocida toxin exhibits pH-sensitive structural stability.
- The toxin's ability to refold suggests a robust, potentially multi-domain structure.
- These findings provide insights into the structural organization of Pasteurella multocida toxin.