Bacteriophage lambda promoters pL and pR: sequence determinants of in vivo activity and of sensitivity to the DNA gyrase inhibitor, coumermycin.

Sequence encompassing the region between bp -43 and +8 of the pL and pR promoters of bacteriophage lambda, as well as sequence variants of these promoters, were compared with respect to their ability to drive a promoterless cat gene in vivo. For both pL- and pR-based promoters, variants with one nonconsensus bp rather than the consensus promoter were found to be maximally active. Determination of promoter function in CSH26 and C600 revealed a marked strain dependence in the activity of some promoter variants. In response to the antibiotic coumermycin, which effects a reduction in DNA superhelical density in vivo, promoters were found to be activated, inhibited or unaffected, depending on their sequence. No simple correlation between a particular response and sequence features of a promoter has become apparent.