Regulatory sequences controlling short chain fatty acid metabolism in Escherichia coli.

Acetoacetate in Escherichia coli is metabolized via the combined enzymatic action of a CoA-transferase and a thiolase. Growth of E. coli on short chain fatty acids such as butyrate and valerate is also predicated upon the expression of these enzymes. The genes for these enzymes (atoDAB) are arranged in an operon and are coordinately transcribed in response to the inducer acetoacetate. A positive regulatory element, the product of the atoC gene, regulates expression of the operon. The atoC gene lies adjacent to the atoDAB operon and all the ato genes have been cloned as a single 6.2 kbp restriction fragment (kindly provided by Dr. Lauren Sallus Jenkins). We have isolated a series of mutant E. coli strains with altered regulatory properties that are either inducible by an alternate substrate, or that show constitutive expression of the atoDAB genes. The -10 and -35 regions upstream of the atoDAB operon poorly match consensus sequences. In addition, the transcriptional start is preceded by a catabolite activator protein binding site (CAP site), as well as a putative binding site for the atoC gene product as represented by a region of dyad symmetry.