TABLE 3.

Effect of upstream sequences from other promoters on lac core promoter activity in vivo

Strain	Promotera	β-Galactosidase activity (Miller units)b	Relative activityc
RLG4282	rrnB P1-lac	1,235	33.3
RLG3283	rrnB P2-lac	492	12.8
RLG3282	RNA II-lac	186	4.9
RLG3281	merT-lac	78	2.0
RLG3280	λ pR-lac	41	1.1
RLG4288	lac(−40)	38	1.0

^aPromoters contained lac core promoter sequence (−37 to +52) and sequence from the indicated promoters upstream of −37 (Fig. 5). 

^bMeasured as described in reference 41. Values are averages of at least two determinations that differ by <10%. 

^cActivities are relative to that of the lac(−40) promoter.