Transcriptional regulation of the cytochrome b562-o complex in Escherichia coli. Gene expression and molecular characterization of the promoter.

Transcriptional regulation of the cyo operon coding for a terminal oxidase, the cytochrome b562-o complex, of the aerobic respiratory chain of Escherichia coli was studied using a chromosomal operon fusion technique with the lacZ gene. Expression of the cyo gene was found to be subject to catabolite repression and also to control by the oxygen concentration. Information on the mechanisms of these regulations was obtained by nucleotide sequencing of the regulatory region, which corresponds to the 5'-flanking region of the cyoA gene. A typical promoter sequence and two noteworthy composite structural features, that is, two potential catabolite gene activator protein-binding sites and a region of hyphenated dyad symmetry were found. The transcription start point was identified by primer extension analysis, confirming the promoter site in the nucleotide sequence. The homology search of the nucleotide sequence in the region of hyphenated dyad symmetry showed a conserved nucleotide sequence in six oxygen-regulated genes examined, which suggests that this is the consensus sequence for the regulation by oxygen.