Clostridium botulinum C2 toxin: binding studies with fluorescence-activated cytometry.

Clostridium botulinum C2 enterotoxin consists of two unlinked proteins designated as C2II, which recognizes a cell-surface glycoprotein and translocates an ADP-ribosyltransferase, C2I, into the cytosol of a targeted cell. Fluorescence-activated cytometry was used to study the cellular interactions of Alexa488-labeled C2I (C2I-A488) and proteolytically activated C2II (C2IIa-A488). The binding of C2IIa-A488 (4 degrees C/10 min) to Chinese hamster ovary (CHO) and African green monkey kidney (Vero) cells yielded a signal/noise ratio of 7:1 and 4:1, respectively.