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Infect Immun, April 1998, p. 1364-1369, Vol. 66, No. 4
Institut für Pharmakologie und
Toxikologie der Albert-Ludwigs-Universität Freiburg, D-79104
Freiburg, Germany
Received 6 November 1997/Returned for modification 31 December
1997/Accepted 16 January 1998
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.
0019-9567/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
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
*
Corresponding author. Mailing address: Institut
für Pharmakologie und Toxikologie der
Albert-Ludwigs-Universität Freiburg, Herman-Herder-Str.
5, D-79104 Freiburg, Germany. Phone: (49) 761-2035301. Fax: (49)
761-2035311. E-mail:
aktories{at}sun2.ruf.uni-freiburg.de.
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