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Clostridium sordellii lethal toxin is maintained in a multimeric protein complex.
Daniel E Voth1, Maen Qa'Dan, Elaine E Hamm
1Department of Botany and Microbiology, The University of Oklahoma, Norman, Oklahoma 73019, USA.
Infection and Immunity
|May 25, 2004
Summary
Clostridium sordellii lethal toxin (TcsL) forms a large, protease-resistant complex at pH 8.0 that hinders cell entry. This complex dissociates at pH 4.0, releasing sensitive polypeptides and enabling cytotoxicity.
Area of Science:
- Microbiology
- Molecular Biology
- Toxicology
Background:
- Large clostridial toxins (LCTs) are potent bacterial toxins.
- Clostridium sordellii lethal toxin (TcsL) exhibits unique pH-dependent intoxication rates.
Purpose of the Study:
- To investigate the molecular mechanisms underlying TcsL's distinct pH-dependent activity.
- To elucidate the structural basis for TcsL's reduced intoxication rate at neutral pH.
Main Methods:
- pH-dependent stability assays
- Sodium dodecyl sulfate (SDS)-agarose gel electrophoresis
- Transmission electron microscopy
- Cytotoxicity assays
- Cross-linking experiments
Main Results:
- TcsL forms a high-molecular-weight (over 750 kDa) protease-resistant complex at pH 8.0.
- This complex dissociates into 45- to 55-kDa polypeptides between pH 4.0 and 5.0.
- Dissociation at low pH enables protease sensitivity and is required for TcsL-mediated cytotoxicity.
- Cytosolic delivery of TcsL's enzymatic domain bypasses cell entry limitations at pH 8.0.
- Complex reassembly after pH shift to 8.0 was not observed.
Conclusions:
- TcsL's intoxication rate is limited by its pH-dependent complex formation and cell entry.
- The dissociation of the TcsL complex at acidic pH is crucial for its cytotoxic activity.
- Understanding TcsL's structural dynamics provides insights into LCT mechanisms.