Glucosylation of Rac1 by recombinant toxins. CT26 cells were either untreated or treated with the indicated amount of native or recombinant TcdA (A) and TcdB (B) for 5 hr. (C) CT26 cells were pretreated with ammonia chloride for 30 min before the exposure of the indicated amount of recombinant toxins for 5 hr. Cells were harvested and western blot was performed as described in the Materials and Methods. Monoclonal antibody clone 102 recognizes unglucosylated Rac1 and has a reduced affinity to glucosylated Rac1.