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Pertussis toxin has eukaryotic-like carbohydrate recognition domains
K Saukkonen1, W N Burnette, V L Mar
1Laboratory of Molecular Infectious Diseases, Rockefeller University, New York, NY 10021.
Summary
Pertussis toxin subunits S2 and S3 bind differently to human cells. Mutating these subunits altered their specific binding targets, revealing insights into bacterial adhesin function.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Bordetella pertussis utilizes adhesins, including pertussis toxin, to bind to human cilia and macrophages.
- Pertussis toxin's B oligomer mediates this cellular recognition through interactions with glycoconjugates.
Purpose of the Study:
- To characterize the cellular recognition properties of the pertussis toxin B oligomer.
- To identify the location and structural requirements of recognition domains within pertussis toxin subunits S2 and S3.
Main Methods:
- Site-directed mutagenesis of recombinant pertussis toxin subunits.
- Differential binding assays using human cilia and macrophages.
- Analysis of carbohydrate recognition specificity.
Main Results:
- Subunits S2 and S3 of the B oligomer exhibit differential recognition of cilia and macrophages, respectively.
- S2 specifically recognizes ciliary lactosylceramide, while S3 binds leukocytic gangliosides.
- Mutations in S2 altered its specificity from lactosylceramide to gangliosides.
- Exchanging amino acid residues 37-52 between S2 and S3 interchanged their target cell specificities.
Conclusions:
- The carbohydrate recognition sequences in pertussis toxin subunits S2 and S3 are distinct and determine target cell specificity.
- These prokaryotic lectin regions show structural and functional similarities to eukaryotic C-type lectin domains.