FIGURE 4.

Inhibition of glucosyltransferase activity in the holotoxin. Recombinant Cdc42 (2 μm) was incubated with UDP-[¹⁴C]glucose (24 μm) and the indicated toxin or toxin fragment (0.1 nm each) for 1 h. The proteins were resolved by SDS-PAGE, and the gels were analyzed by phosphorimaging. A, comparison of GTD and HT activity of TcdA (gray bars) and TcdB (white bars) (n = 4). Activity is inhibited in the holotoxins. B, TcdA GTD(1–542), TcdA(1–800), TcdA(1–1832), and TcdA HT(1–2710) were tested for their capacity to modify Cdc42 (n = 3). The activity of the 1–800, 1–1832, and 1–2710 proteins was reduced relative to GTD but was increased after induction of autoprocessing. Band intensities were quantified, and the data were scaled with the average value for Cdc42 modified by TcdA GTD set at 1. Error bars, S.D. Insets show representative experiments.