title: Complete subunit structure of the Clostridium botulinum type D toxin complex via intermediate assembly with nontoxic components.
abstract: Clostridium botulinum serotype D strains usually produce two types of stable toxin complex (TC), namely, the 300 kDa M (M-TC) and the 660 kDa L (L-TC) toxin complexes. We previously proposed assembly pathways for both TCs [Kouguchi, H., et al. (2002) J. Biol. Chem. 277, 2650-2656]: M-TC is composed by association of neurotoxin (NT) and nontoxic nonhemagglutinin (NTNHA); conjugation of M-TC with three auxiliary types of hemagglutinin subcomponents (HA-33, HA-17, and HA-70) leads to the formation of L-TC. In this study, we found three TC species, 410, 540, and 610 kDa TC species, in the culture supernatant of type D strain 4947. The 540 and 610 kDa TC species displayed banding patterns on SDS-PAGE similar to that of L-TC but with less staining intensity of the HA-33 and HA-17 bands than those of L-TC, indicating that these are intermediate species in the pathway to L-TC assembly. In contrast, the 410 kDa TC species consisted of M-TC and two molecules of HA-70. All of the TC species, except L-TC, demonstrated no hemagglutination activity. When the intermediate TC species were mixed with an isolated HA-33/17 complex, every TC species converted to 650 kDa L-TC with full hemagglutination activity and had the same molecular composition of L-TC. On the basis of titration analysis with the HA-33/17 complex, the stoichiometry of the HA-33/17 complex molecules in the L-TC, 610 kDa, and 540 kDa TC species was estimated as 4, 3, and 2, respectively. In conclusion, the complete subunit composition of mature L-TC is deduced to be a dodecamer assembled by a single NT, a single NTNHA, two HA-70, four HA-33, and four HA-17 molecules.
authors.affiliation: Department of Food Science and Technology, Faculty of Bioindustry, Tokyo University of Agriculture, 196 Yasaka, Abashiri 099-2493, Japan.
authors.forename: Shingo
authors.initials: S
authors.lastname: Mutoh
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Kouguchi
authors.forename: Yoshimasa
authors.initials: Y
authors.lastname: Sagane
authors.forename: Tomonori
authors.initials: T
authors.lastname: Suzuki
authors.forename: Kimiko
authors.initials: K
authors.lastname: Hasegawa
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Watanabe
authors.forename: Tohru
authors.initials: T
authors.lastname: Ohyama
mesh_terms: D000596:Amino Acids / Q000737:chemistry; D001905:Botulinum Toxins / Q000737:chemistry*; D002850:Chromatography, Gel; D003014:Clostridium botulinum / Q000737:chemistry*; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D006384:Hemagglutination; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary
chemical_list: D000596:Amino Acids; C096325:botulinum toxin type D; D001905:Botulinum Toxins