title: Structural analysis by X-ray crystallography and calorimetry of a haemagglutinin component (HA1) of the progenitor toxin from Clostridium botulinum.
abstract: Botulism food poisoning is caused primarily by ingestion of the Clostridium botulinum neurotoxin (BoNT). The 1300 amino acid BoNT forms a progenitor toxin (PTX) that, when associated with a number of other proteins, increases its oral toxicity by protecting it from the low pH of the stomach and from intestinal proteases. One of these associated proteins, HA1, has also been suggested to be involved with internalization of the toxin into the bloodstream by binding to oligosaccharides lining the intestine. Here is reported the crystal structure of HA1 from type C Clostridium botulinum at a resolution of 1.7 Angstrom. The protein consists of two beta-trefoil domains and bears structural similarities to the lectin B-chain from the deadly plant toxin ricin. Based on structural comparison to the ricin B-chain lactose-binding sites, residues of type A HA1 were selected and mutated. The D263A and N285A mutants lost the ability to bind carbohydrates containing galactose moieties, implicating these residues in carbohydrate binding.
authors.affiliation: Pharmacogenetic Section Laboratory of Reproductive and Developmental Toxicology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA.
authors.forename: Kaoru
authors.initials: K
authors.lastname: Inoue
authors.affiliation: Pharmacogenetic Section Laboratory of Reproductive and Developmental Toxicology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA.
authors.forename: Mack
authors.initials: M
authors.lastname: Sobhany
authors.affiliation: Laboratory of Structural Biology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA.
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Transue
authors.affiliation: Department of Bacteriology, Okayama University Medical School, 2-5-1 Shikata-cho, Okayama 700-8558, Japan.
authors.forename: Keiji
authors.initials: K
authors.lastname: Oguma
authors.affiliation: Laboratory of Structural Biology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA.|Pharmacogenetic Section Laboratory of Reproductive and Developmental Toxicology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA.
authors.forename: Lars C
authors.initials: LC
authors.lastname: Pedersen
authors.affiliation: Pharmacogenetic Section Laboratory of Reproductive and Developmental Toxicology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA.
authors.forename: Masahiko
authors.initials: M
authors.lastname: Negishi
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D001905:Botulinum Toxins / Q000737:chemistry* / Q000235:genetics / Q000633:toxicity; D002151:Calorimetry; D002240:Carbohydrate Sequence; D003014:Clostridium botulinum / Q000737:chemistry* / Q000235:genetics / Q000472:pathogenicity; D018360:Crystallography, X-Ray; D004269:DNA, Bacterial / Q000235:genetics; D006388:Hemagglutinins / Q000737:chemistry* / Q000235:genetics / Q000633:toxicity; D006801:Humans; D008024:Ligands; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009844:Oligosaccharides / Q000737:chemistry; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid
chemical_list: D004269:DNA, Bacterial; D006388:Hemagglutinins; D008024:Ligands; D009844:Oligosaccharides; D001905:Botulinum Toxins