title: Identification and partial characterization of a low affinity metal-binding site in the light chain of tetanus toxin.
abstract: Tetanus toxin was shown to contain a metal-binding site for zinc and copper. Equilibrium dialysis binding experiments using 65Zn indicated an association constant of 9-15 microM, with one zinc-binding site/toxin molecule. The zinc-binding site was localized to the toxin light chain as determined by binding of 65Zn to the light chain but not to the heavy chain after separation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and transfer to Immobilon membranes. Copper was an efficient inhibitor of 65Zn binding to tetanus toxin and caused two peptide bond cleavages in the toxin light chain in the presence of ascorbate. These metal-catalyzed oxidative cleavages were inhibited by the presence of zinc. Partial characterization of metal-catalyzed oxidative modifications of a peptide based on a putative metal-binding site (HELIH) in the toxin light chain was used to map the metal-binding site in the protein.
authors.affiliation: Département de Biologie Moléculaire et Structurale, Unité Institut National de la Santé et de la Recherche Médicale 238, Grenoble, France.
authors.forename: J F
authors.initials: JF
authors.lastname: Wright
authors.forename: M
authors.initials: M
authors.lastname: Pernollet
authors.forename: A
authors.initials: A
authors.lastname: Reboul
authors.forename: C
authors.initials: C
authors.lastname: Aude
authors.forename: M G
authors.initials: MG
authors.lastname: Colomb
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002413:Cations, Divalent; D003300:Copper / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D008969:Molecular Sequence Data; D016339:Spectrometry, Mass, Fast Atom Bombardment; D013744:Tetanus Toxin / Q000378:metabolism*; D015032:Zinc / Q000378:metabolism*
chemical_list: D002413:Cations, Divalent; D013744:Tetanus Toxin; D003300:Copper; D015032:Zinc