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Infection and Immunity, August 2000, p. 4566-4573, Vol. 68, No. 8
Institut für Pharmakologie und
Toxikologie1 and Institut für
Biologie II,2 Albert-Ludwigs-Universität
Freiburg, D-79104 Freiburg, and Lehrstuhl für
Biotechnologie, Theodor-Boveri-Institut (Biozentrum) der
Universität Würzburg, D-97074
Würzburg,3 Germany, and
Microbiology and Molecular Genetics, Medical College of
Wisconsin, Milwaukee, Wisconsin 532264
Received 24 March 2000/Returned for modification 25 April
2000/Accepted 18 May 2000
The binary Clostridium botulinum C2 toxin consists of
two separate proteins, the binding component C2II (80.5 kDa) and the actin-ADP-ribosylating enzyme component C2I (49.4 kDa). For its cytotoxic action, C2II binds to a cell membrane receptor and induces cell entry of C2I via receptor-mediated endocytosis. Here we studied the structure-function relationship of C2II by constructing truncated C2II proteins and producing polyclonal antisera against selective regions of C2II. An antibody raised against the C terminus (amino acids
592 to 721) of C2II inhibited binding of C2II to cells. The antibody
prevented pore formation by C2II oligomers in artificial membranes but
did not influence the properties of existing channels. To further
define the region responsible for receptor binding, we constructed
proteins with deletions in C2II; specifically, they lacked amino acid
residues 592 to 721 and the 7 C-terminal amino acid residues. The
truncated proteins still formed sodium dodecyl sulfate-stable oligomers
but were unable to bind to cells. Our data indicate that the C terminus
of C2II mediates binding of the protein to cells and that the 7 C-terminal amino acids are structurally important for receptor binding.
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
The C Terminus of Component C2II of
Clostridium botulinum C2 Toxin Is Essential for
Receptor Binding
*
Corresponding author. Mailing address: Institut
für Pharmakologie und Toxikologie, Hermann-Herder-Str. 5, D-79104
Freiburg, Germany. Phone: 49-761-2035301. Fax: 49-761-2035311. E-mail:
aktories{at}uni-freiburg.de.
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