title: The N-terminal part of the enzyme component (C2I) of the binary Clostridium botulinum C2 toxin interacts with the binding component C2II and functions as a carrier system for a Rho ADP-ribosylating C3-like fusion toxin.
abstract: The binary actin-ADP-ribosylating Clostridium botulinum C2 toxin consists of the enzyme component C2I and the binding component C2II, which are separate proteins. The active component C2I enters cells through C2II by receptor-mediated endocytosis and membrane translocation. The N-terminal part of C2I (C2IN), which consists of 225 amino acid residues but lacks ADP-ribosyltransferase activity, was identified as the C2II contact site. A fusion protein (C2IN-C3) of C2IN and the full-length C3-like ADP-ribosyltransferase from Clostridium limosum was constructed. The fusion protein C2IN-C3 ADP-ribosylated Rho but not actin in CHO cell lysates. Together with C2II, C2IN-C3 induced complete rounding up of CHO and HeLa cells after incubation for 3 h. No cell rounding was observed without C2II or with the original C3-like transferase from C. limosum. The data indicate that the N-terminal 225 amino acid residues of C2I are sufficient to cause the cellular uptake of C. limosum transferase via the binding component of C2II, thereby increasing the cytotoxicity of the C3-like exoenzyme several hundred-fold.
authors.affiliation: Institut für Pharmakologie und Toxikologie der Albert-Ludwigs-Universität Freiburg, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Barth
authors.forename: F
authors.initials: F
authors.lastname: Hofmann
authors.forename: C
authors.initials: C
authors.lastname: Olenik
authors.forename: I
authors.initials: I
authors.lastname: Just
authors.forename: K
authors.initials: K
authors.lastname: Aktories
mesh_terms: D036002:ADP Ribose Transferases / Q000378:metabolism* / Q000633:toxicity; D000246:Adenosine Diphosphate Ribose / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D001905:Botulinum Toxins / Q000378:metabolism* / Q000633:toxicity; D016466:CHO Cells; D003001:Cloning, Molecular; D006224:Cricetinae; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism* / Q000633:toxicity; D020743:rhoB GTP-Binding Protein
chemical_list: D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins; D000246:Adenosine Diphosphate Ribose; D036002:ADP Ribose Transferases; C063007:exoenzyme C3, Clostridium botulinum; D001905:Botulinum Toxins; D019204:GTP-Binding Proteins; D020743:rhoB GTP-Binding Protein