Table 1.

Effect of inserting base pairs between the two halves of the VirB binding site.

	Average relative β-galactosidase activity (%)
	Wild-type S. flexneri (2457T)	virB mutant (AWY3)
PicsP-lacZ	100	6 ± 1*
2 bp insertion	8 ± 1*	6 ± 1*
3 bp insertion	7 ± 1*	6 ± 1*
4 bp insertion	7 ± 1*	7 ± 1*
Promoterless lacZ	3 ± 0*	6 ± 1*

All data are statistically different (t-test) from the average relative activity observed in wild-type S. flexneri carrying PicsP-lacZ, (P < 0.05).