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Proteins released during high toxin production in Clostridium difficile
Kakoli Mukherjee1, Sture Karlsson2,3, Lars G Burman3
1AstraZeneca Research Center India, PO Box 359 Malleswaram, 560 003 Bangalore, India3.
Microbiology (Reading, England)
|July 9, 2002
Summary
Clostridium difficile releases toxins A and B via Sec-dependent and holin-like pathways, not lysis. This study identified shed S-layer proteins as the most abundant extracellular proteins during toxin production.
Area of Science:
- Microbiology
- Molecular Biology
- Protein Secretion
Background:
- The secretion mechanisms of Clostridium difficile toxins A and B are largely unknown.
- Limited information exists regarding other extracellular proteins produced by C. difficile.
Purpose of the Study:
- To identify exported proteins from C. difficile VPI 10463 under conditions of high toxin production.
- To elucidate the secretion pathways utilized by C. difficile.
Main Methods:
- Analysis of extracellular proteins during stationary phase.
- Mass spectrometry and N-terminal sequencing for protein identification.
- PCR-based methods for gene analysis.
Main Results:
- Toxins A and B were secreted in a 1:1 ratio, constituting up to 50% of extracellular proteins, indicating active secretion rather than lysis.
- A 47 kDa protein with weak similarity to TolC and an unprocessed protein similar to Bacillus subtilis XkdK were identified.
- Shed S-layer proteins were the most abundant extracellular proteins, showing significant sequence variation in the slpA gene.
Conclusions:
- Clostridium difficile employs both classical Sec-dependent and potentially holin-like pathways for protein secretion.
- The bacterium secretes a limited set of proteins, including toxins and S-layer proteins, through these identified mechanisms.