Molecular and functional characterization of a carbon starvation gene of Escherichia coli

Escherichia coli induces the synthesis of at least 30 proteins at the onset of carbon starvation, two-thirds of which are positively regulated by the cyclic AMP (cAMP) and cAMP receptor protein (CRP) complex. Two of the cAMP-CRP-dependent genes mapped to 14 and 93 minutes of the chromosome and are designated cstA and cstB, respectively. The cstA promoter region was cloned and localized to a 600 base-pair fragment downstream from the iron-regulated entCEBA-P15 operon. Carbon starvation-inducible transcription initiated at three sites spaced one turn of the DNA helix apart. All had--10 sequences similar to consensus E sigma 70 promoters and poor--35 sequences. Deletion of a putative CRP binding site abolished carbon starvation-mediated induction. Sequence analysis of the cstA coding region revealed the presence of three sequential open reading frames potentially encoding two hydrophobic proteins of 60,223 Da and 15,201 Da and a hydrophilic protein of 7467 Da. Overexpression of the cstA region produced starvation-inducible proteins of the expected sizes. Suggestive evidence was obtained that cstA is involved in peptide utilization.