DNA sequence and transcriptional organization of essential cell division genes ftsQ and ftsA of Escherichia coli: evidence for overlapping transcriptional units.

The DNA sequence of a cloned segment of the Escherichia coli chromosome containing ftsQ, ftsA, and part of the ftsZ gene was determined and interpreted for genetic complementation and promoter fusion data for the region. The contiguous genes ftsQ, ftsA, and ftsZ were transcribed in the same direction (clockwise on the genetic map) and each had at least one associated promoter which allowed it to be transcribed independently of neighboring genes. ftsA and ftsZ possessed promoters within the coding sequences of the juxtaposed upstream structural genes, and a promoter element for ftsA was surrounded by a region of twofold symmetry which corresponded closely to a symmetrical element in the region of a putative ftsZ promoter. The structural gene of ftsQ consisted of 838 nucleotides, encoding a 276-residue amino acid polypeptide of molecular weight 31,400; the structural gene of ftsA consisted of 1,260 nucleotides, encoding a 420-residue amino acid polypeptide of molecular weight 45,400. The observation that the termination codon of ftsQ overlaps with a potential initiation codon for ftsA suggested that these two genes may be translationally coupled when transcription is initiated upstream of the ftsQ coding sequence.