Fig. 7. (A) Lipase activity of rExoU. Purified His-tagged proteins at the indicated concentrations were added to an in vitro assay with ¹⁴C-labeled liposomes. In some cases purified proteins were preincubated with a yeast extract (+ extract) before addition to the labeled liposomes. The release of free fatty acids was measured using TLC. (B) The activity of an rExoU-replete (ExoU + extract) and an rExoU-depleted yeast extract was quantified by fatty acid release. Removal of rExoU from the treated yeast extract was accomplished using cobalt beads (97.6% reduction in protein as assessed by western blot analysis). Lipase activity was reduced by 98.1% upon removal of His-tagged rExoU.