Figure 1.

ftsZ is transcribed from one promoter. (A) A partial restriction map of the ftsAZ region is shown with the boundaries of ddl, ftsQ, ftsA, and ftsZ indicated by arrows. ρ-independent terminators are indicated by T. The lines show the different fragments that were subcloned into the pRKlac290 promoter probe plasmid. β-Galactosidase activities are the average of at least four independent assays with s.d. <10%. The approximate location of the ftsZ promoter is indicated with a bent arrow. In plac290/E1, the open box with a Δ represents a deletion of the HpaI fragment. (B) Determination of the ftsZ transcription start site by primer extension and S1 nuclease mapping. Both reactions (P for primer extension and S for S1 nuclease mapping) were run with a dideoxy-sequencing reaction using a primer with the same 5′ end as the primer extension primer (oligonucleotide ftsZPE1) and the S1 probe. The DNA sequence corresponding to the promoter is shown between the two reactions and the −10 and −35 regions are boxed. The cDNA product common to primer extension and S1 mapping is indicated by an arrow and an asterisk indicates the transcription start site in the DNA sequence. The position of the DdeI and the HpaI sites is indicated.