Regulation of the divergent guaBA and xseA promoters of Escherichia coli by the cyclic AMP receptor protein.

The gua promoter (guaP) of Escherichia coli resembles those for ribosomal RNA (rrn) operons and lies in a close back-to-back arrangement with the promoter for xseA (xseP). Transcription from guaP is subject to stringent control and growth-rate-dependent regulation, and to repression by DnaA and PurR. In addition, transcription from guaP is regulated by the cyclic AMP receptor protein (CRP).

The purB gene of Escherichia coli K-12 is located in an operon.

The structural gene (purB) for succinyl-AMP (S-AMP) lyase and three additional ORFs are on the same DNA strand of the chromosome of Escherichia coli. Cassette mutagenesis and primer extension mapping demonstrated that purB is co-transcribed with an upstream gene (ORF23, or ycfC) encoding a 22.9 kDa membrane-associated protein of non-essential, but unknown, function unrelated to purine biosynthesis.

Specific binding of DnaA protein to a DnaA box in the guaB gene of Escherichia coli K12.

Expression of the guaBA operon of Escherichia coli is regulated by the DNA replication-initiating protein, DnaA. Two DnaA boxes, which are potential binding sites for DnaA, are present in the gua operon. One box (with 8/9 match to the DnaA box consensus sequence) is at the gua promoter; the other box, which has a consensus sequence, is on the non-transcribed strand within the guaB coding region approximately 200 bp downstream of the initiation codon.

Stringent and growth-rate-dependent control of the gua operon of Escherichia coli K-12.

The promoter of the gua operon has been located by transcript mapping using primer extension with reverse transcriptase. The surrounding nucleotide sequence has features characteristic of promoters under stringent and growth-rate-dependent regulation, namely a GC-rich discriminator next to the -10 hexamer, an upstream AT-rich sequence (the UP element) and potential FIS-binding sites. Transcriptional activity of the gua promoter was examined using transcriptional fusions to lacZ placed at a single chromosomal location.

Regulation of the gua operon of Escherichia coli by the DnaA protein.

The guaBA operon determines production of the two enzymes required to convert hypoxanthine to guanine at the nucleotide level during guanine nucleotide biosynthesis. Two DnaA boxes, binding sites for the DNA replication-initiating DnaA protein, are present in the gua operon, one at the gua promoter (guaP) and the other within the guaB coding sequence. Regulation of the guaBA operon by DnaA protein was studied using strains carrying chromosomal gua-lacZ fusions.