Fig. 3.

Relative transcriptional activation for wild-type and mutated promoters. (a) Sequences of the consensus PhoP-box, the PhoP-boxes of the wild-type promoters, and the PhoP-boxes of the mutated promoters. Hybrid 1 consists of the mgtA promoter with the mgrB PhoP-box. Hybrid 2 and hybrid 3 consist of the mgrB promoter with the mgtA PhoP-box and with portions of flanking mgtA sequence, respectively. (b) Fold increase in transcription of wild-type promoters (relative to the fold increase of mgrB transcription) for cells grown in 100 μM Mg²⁺ compared with 10 mM Mg²⁺. Fold increase is defined to be the following: [(YFP/CFP)_{100 μM Mg²⁺} − (YFP/CFP)_{100 μM Mg²⁺,ΔphoQ}]/[YFP/CFP)_{10 mM Mg²⁺} − (YFP/CFP)_{10 mM Mg²⁺,ΔphoQ}]. (c) Fold increase as in b for several mutated promoters listed in a. Two different23 versions of the mgtA reporter are also compared. UTR1 has the native 5′-UTR for mgtA, which includes a potential riboswitch. UTR2 has a truncated 5′-UTR with only 16 base pairs of the original 263 base pairs in the mgtA 5′-UTR. (d) Fold increase in transcription of various promoters (relative to the fold increase of mgrB transcription) for cells exposed to LL-37 in 100 μM Mg²⁺ for 1 h, compared with cells in 100 μM Mg²⁺ without LL-37. Fold increases were computed by using YFP/CFP values determined from two independent cultures. The bars denote estimates of the error determined from the corresponding ranges of the YFP/CFP measurements.