FIG. 4.

Mutations in the vacA −10 promoter element. Mutations were introduced into the vacA −10 region of a reporter strain (H. pylori 60190 VX-1), which contains a vacA::xylE transcriptional fusion. Strain 60190 VX-1 CAT control is a vacA::xylE reporter strain that contains a CAT gene at the 3′ end of cysS but no changes in vacA promoter sequences (8). Strain 60190 VPC1/VX-1 contains a 6-bp substitution for the native −10 vacA hexamer. Other strains contain single nucleotide substitutions at the −15, −14, −13, and −12 positions of the vacA promoter. Sites of nucleotide substitutions are indicated by asterisks. The XylE specific activity of each strain is shown on the right. These values represent the means ± standard deviations for triplicate independent assays. P values represent comparisons with the XylE specific activity of the control strain (60190 VX-1 CAT control). OD₆₀₀, optical density at 600 nm.