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Anthrax toxin lethal factor contains a zinc metalloprotease consensus sequence which is required for lethal toxin
K R Klimpel1, N Arora, S H Leppla
1Laboratory of Microbial Ecology, National Institute of Dental Research, National Institutes of Health, Bethesda, Maryland 20892.
Molecular Microbiology
|September 1, 1994
Summary
Anthrax toxin
Area of Science:
- Biochemistry
- Molecular Biology
- Toxicology
Background:
- Anthrax toxin lethal factor (LF) is a key component of anthrax pathogenesis.
- The enzymatic activity of LF is crucial for its lethal effects.
- The precise catalytic mechanism of LF was not fully understood.
Purpose of the Study:
- To determine if anthrax toxin LF possesses metallopeptidase activity.
- To identify the catalytic site and zinc-binding residues of LF.
Main Methods:
- Sequence homology searches to identify potential metalloprotease motifs.
- Inhibition assays using known protease inhibitors.
- Site-directed mutagenesis to alter putative catalytic residues.
- Zinc-binding assays using 65Zn.
Main Results:
- LF shares sequence similarity with zinc-binding metalloproteases (HEXXH motif).
- Protease inhibitors (bestatin, captopril) blocked LF intoxication.
- Mutagenesis of H-686, H-690, and E-687 inactivated LF activity.
- LF demonstrated zinc binding, which was reduced in mutants.
- Mutations at E-720 and E-721 did not affect LF activity.
Conclusions:
- Anthrax toxin LF is a zinc metallopeptidase.
- The catalytic activity of LF is responsible for its lethal effects.
- Understanding LF's enzymatic function provides targets for therapeutic intervention.