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[Construction of plasmids coding for diphtheria toxin fragments]
Molekuliarnaia Biologiia
|September 1, 1988
Summary
Researchers constructed diphtheria toxin toxoids and observed their secretion in E. coli and Erwinia carotovora. These toxoids undergo proteolysis, generating fragments, with E. coli signal peptidase potentially involved in specific cleavage.
Area of Science:
- Molecular Biology
- Bacteriology
- Toxicology
Background:
- Diphtheria toxin is a potent bacterial toxin.
- Nontoxic derivatives (toxoids) are crucial for vaccine development.
- Understanding toxoid secretion and processing is key for effective antitoxin therapies.
Purpose of the Study:
- To construct plasmids encoding diphtheria toxin toxoids.
- To investigate the secretion and processing of these toxoids in bacterial hosts (E. coli and Erwinia carotovora).
- To identify proteolysis targets within the secreted toxoids.
Main Methods:
- Plasmid construction for expressing diphtheria toxin toxoids.
- Bacterial expression in E. coli and E. carotovora.
- Analysis of toxoid localization (periplasmic vs. cytoplasmic).
- Proteolytic cleavage analysis using molecular weight determination.
Main Results:
- Constructed plasmids successfully produced diphtheria toxin toxoids.
- Toxoids with signal sequences were secreted into the periplasmic space of E. coli and E. carotovora.
- Toxoids lacking signal sequences remained in the cytoplasm.
- Secreted toxoids underwent limited proteolysis, yielding fragments.
- Three primary proteolysis targets were identified: one between the A and B fragments, and two within the B fragment.
Conclusions:
- Diphtheria toxin toxoids can be secreted by E. coli and E. carotovora.
- Proteolysis of secreted toxoids occurs, generating specific fragments.
- E. coli signal peptidase may play a role in the targeted cleavage of diphtheria toxin toxoids.