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Mol Gen Genet. 1997 May 20;254(5):599-603.

Roles of RpoS (sigmaS), IHF and ppGpp in the expression of the hmp gene encoding the flavohemoglobin (Hmp) of Escherichia coli K-12.

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The Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, The University of Sheffield, UK.


The Escherichia coli K-12 gene hmp encodes the flavohemoglobin Hmp. A hmp promoter phi(hmp-lacZ)-operon fusion was constructed in the chromosome and its activity measured during the growth cycle. Logarithmically growing cultures had low levels of phi(hmp-lacZ) expression, which increased two-fold at the onset of stationary phase in rich medium. The effect was abolished in a strain carrying a null allele of the gene rpoS encoding the stationary phase-specific sigma subunit of RNA polymerase sigmaS. A himA mutation resulted in a 1.5-fold increase in expression of phi(hmp-lacZ) but did not affect growth phase-dependent regulation. A single transcriptionial start site was found for hmp, located 38 bp upstream of the initiation codon. Putative Fnr boxes at positions -2 to +11 occur in the hmp promoter region.

[Indexed for MEDLINE]

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