FIG. 3.

Regions 1 to 5 of ExoU are required for PLA₂ activity. PLA₂ activity is expressed as a percentage of the activity observed with wild-type ExoU. Bee venom, which has potent PLA₂ activity, was used as a positive control. Vector refers to yeast containing empty vector, and ExoU refers to yeast expressing wild-type ExoU. The PLA₂ activities of ExoU with representative mutations in each of regions 1 to 5 are shown. E607W is an amino acid substitution mutant that retained cytotoxicity and is therefore used as a control. ExoUΔ624-687 is a noncytotoxic deletion mutant of ExoU lacking the C-terminal 64 amino acids, and ExoUΔ657-687 is a partially noncytotoxic deletion mutant lacking the C-terminal 31 amino acids. R1 to R5 refer to regions 1 to 5, respectively. Each assay was performed in triplicate. Error bars represent standard errors of the means.