Formation of a biologically active toxin complex of the binary Clostridium botulinum C2 toxin without cell membrane interaction.

Clostridium botulinum produces a binary toxin, which is composed of two separate proteins. The enzyme component, C2I, is an ADP-ribosyltransferase which modifies G-actin of eukaryotic cells. The proteolytically activated binding/translocation component, C2IIa, forms ring-shaped heptamers, which bind to cell receptors and mediate the transport of C2I into the cytosol of target cells.

Purification and activity of the Rho ADP-ribosylating binary C2/C3 toxin.

C3 exoenzyme from Clostridium limosum, specifically ADP-ribosylates and inactivates Rho GTPases, but not or much less than Rac and Cdc42. To bypass the poor cell accessibility of the exoenzyme, a chimeric fusion toxin was constructed consisting of C3 exoenzyme and the N-terminal adaptor domain of the enzyme component C2I of the actin-ADP-ribosylating Clostridium botulinum C2 toxin. This fusion toxin C2IN-C3 is transported into cells by interaction with the binding and translocation component (C2II) of C2 toxin.

The host cell chaperone Hsp90 is necessary for cytotoxic action of the binary iota-like toxins.

The heat shock protein Hsp90 is essential for uptake of the binary actin ADP-ribosylating toxins Clostridium perfringens iota-toxin and Clostridium difficile transferase into eukaryotic cells. Inhibition of Hsp90 by its specific inhibitor radicicol delayed intoxication of Vero cells by these toxins. A common Hsp90-dependent mechanism for their translocation is discussed.

Cellular uptake of Clostridium botulinum C2 toxin: membrane translocation of a fusion toxin requires unfolding of its dihydrofolate reductase domain.

The Clostridium botulinum C2 toxin is the prototype of the family of binary actin-ADP-ribosylating toxins. C2 toxin is composed of two separated nonlinked proteins. The enzyme component C2I ADP-ribosylates actin in the cytosol of target cells.

Clostridium botulinum C2 toxin: low pH-induced pore formation is required for translocation of the enzyme component C2I into the cytosol of host cells.

The binary Clostridium botulinum C2 toxin consists of two individual proteins, the transport component C2II (80 kDa) and the enzyme component C2I, which ADP-ribosylates G-actin in the cytosol of cells. Trypsin-activated C2II (C2IIa) forms heptamers that bind to the cell receptor and mediate translocation of C2I from acidic endosomes into the cytosol of target cells. Here, we report that translocation of C2I across cell membranes is accompanied by pore formation of C2IIa.

The host cell chaperone Hsp90 is essential for translocation of the binary Clostridium botulinum C2 toxin into the cytosol.

Clostridium botulinum C2 toxin is the prototype of the binary actin-ADP-ribosylating toxins and consists of the binding component C2II and the enzyme component C2I. The activated binding component C2IIa forms heptamers, which bind to carbohydrates on the cell surface and interact with the enzyme component C2I. This toxin complex is taken up by receptor-mediated endocytosis.