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Infection and Immunity, April 2002, p. 1909-1914, Vol. 70, No. 4
0019-9567/02/$04.00+0 DOI: 10.1128/IAI.70.4.1909-1914.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.
Department of Microbiology, Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Yamashiro-cho, Tokushima 770-8514, Japan
Received 16 October 2001/ Returned for modification 19 November 2001/ Accepted 28 November 2001
Clostridium perfringens iota-toxin is a binary toxin consisting of two individual proteins, the binding component (Ib) and the enzyme component (Ia). Wild-type Ib bound to Vero cells at 4 and 37°C and formed oligomers at 37°C but not at 4°C. The Ib-induced K+ release from the cells was dependent on the oligomer formation of Ib in the cells, but the oligomer formation did not induce rounding activity or cytotoxicity. After incubation of the cells with recombinant Ib (rIb) at 37°C, the Ib oligomer in the cell became resistant to pronase treatment with time, but the Ib monomer was sensitive to the treatment. Furthermore, treatment of Vero cells with rIb in the presence of bafilomycin, methylamine, or ethylamine resulted in accumulation of the oligomer in the cells but had no effect on K+ release. Moreover, incubation with Ib plus Ia in the presence of these agents caused no rounding in the cells. These observations suggest that Ib binds to Vero cells, itself oligomerizing to form ion-permeable channels and that the formation of oligomer then induces endocytosis.
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