Activation of Clostridium botulinum type E toxin purified by two different procedures

Area of Science:

• Microbiology
• Toxicology
• Protein Chemistry

Background:

• Clostridium botulinum type E produces a potent neurotoxin.
• Toxin purification methods can influence its properties.
• Understanding toxin structure-activity relationships is crucial.

Purpose of the Study:

• To compare Clostridium botulinum type E toxin purified from culture supernates and cell extracts.
• To investigate the effects of purification conditions and trypsin activation on toxin properties.
• To elucidate differences in molecular conformation and specific activity.

Main Methods:

• Purification of Clostridium botulinum type E toxin from culture supernates and cell extracts.
• Toxin activity assay using mouse LD50.
• Trypsin activation and SDS-polyacrylamide gel electrophoresis.
• Agar gel double-immunodiffusion for antigenic specificity.
• 125I labeling and chymotryptic peptide mapping.

Main Results:

• Toxin from cell extract had lower specific activity than toxin from culture supernate.
• Both toxins were activated by trypsin, with higher fold-activation for cell extract toxin.
• SDS-PAGE revealed a Mr 144,000 band before and Mr 100,000/55,000 bands after trypsin treatment.
• Peptide maps showed differences before trypsin treatment but similarity after activation.
• Antigenic specificity remained unchanged after trypsin treatment.

Conclusions:

• Clostridium botulinum type E toxin from culture fluid is a partially activated form.
• The molecular conformation of toxin differs between culture supernate and cell extract preparations.
• Differences in specific activity and trypsin activation are likely due to conformational variations.