Regulation of the ato operon by the atoC gene in Escherichia coli.
The expression of the Ato enzymes, acetyl coenzyme A:acetoacetyl coenzyme A transferase and thiolase II, is required for growth of Escherichia coli on short-chain fatty acids. The structural genes for these enzymes, atoD, atoA, and atoB, respectively, make up the ato operon. A 48-kilodalton protein encoded by atoC was required for the synthesis or activation of the Ato enzymes. The expression of Ato enzyme activities was inducible in atoC+ strains, constitutive in atoCc strains, and noninducible in atoC mutants. Merodiploid studies demonstrated that the atoCc allele is trans-dominant to the atoC+ allele. To study the action of the trans-acting atoC-encoded activator, the promoter of the ato operon was fused to the promoterless galK gene and introduced into a low-copy-number vector. The resulting low-copy-number fusion plasmid was introduced into atoC+, atoC, and atoCc hosts. The expression of the fused galK gene was inducible in the atoC+ host, noninducible in atoC host strains, and constitutive when harbored in the atoCc host. This indicated that the atoC+ and atoCc gene products act at the level of transcription, stimulating the expression of the ato operon. A working model consistent with these results is presented.
D000090:Acetoacetates / Q000378:metabolism*; D000101:Acetyl-CoA C-Acetyltransferase / Q000235:genetics; D002087:Butyrates / Q000378:metabolism; D003001:Cloning, Molecular; D015256:Coenzyme A-Transferases; D004268:DNA-Binding Proteins / Q000235:genetics; D004790:Enzyme Induction; D004926:Escherichia coli / Q000235:genetics*; D005786:Gene Expression Regulation; D005798:Genes, Bacterial; D009876:Operon; D011401:Promoter Regions, Genetic; D013466:Sulfurtransferases / Q000235:genetics
D000090:Acetoacetates; D002087:Butyrates; D004268:DNA-Binding Proteins; C016635:acetoacetic acid; D000101:Acetyl-CoA C-Acetyltransferase; D013466:Sulfurtransferases; D015256:Coenzyme A-Transferases; C026389:acetyl-CoA-acetoacetate CoA transferase