Fig. 3. YopE toxicity is dependent on RhoGAP activity. (A) Purified His-tagged YopE and mutant (R144A) YopE-R144A (5.5 pmol) were incubated with G-proteins (GST–Rac1, GST–RhoA, GST–Cdc42 and GST–H-Ras) (5.5 pmol) that were pre-loaded with [γ-³²P]GTP. (His₆-tagged YopE-R144A was not incubated with GST–H-Ras.) GTPase activity was assayed after 5 min. Values represent the mean ± SD of three separate experiments. (B) Growth assays (as described in Figure 2) were conducted on cells transformed with a high-copy-number plasmid encoding galactose-inducible mutant GFP-yopE (R144A) and compared to cells transformed with empty vector or wild-type GAL10-GFP-yopE.