PMID:8932315

Citation	Bsat, N, Chen, L and Helmann, JD (1996) Mutation of the Bacillus subtilis alkyl hydroperoxide reductase (ahpCF) operon reveals compensatory interactions among hydrogen peroxide stress genes. J. Bacteriol. 178:6579-86
Abstract	In Bacillus subtilis, hydrogen peroxide induces the synthesis of catalase (KatA), alkyl hydroperoxide reductase (AhpCF), and a DNA-binding protein of the Dps family (MrgA). KatA, AhpCF, heme biosynthesis enzymes, and MrgA are also induced upon entry into stationary phase under conditions of iron and manganese limitation. In an effort to define the peroxide regulon repressor, PerR, we used mini-Tn10 mutagenesis to identify loci affecting the regulation of mrgA. From this screen, we isolated two mini-Tn10 insertions in ahpC, the gene encoding the small subunit of AhpCF, that increase the transcription of mrgA-lacZ even in iron-supplemented minimal medium. Indeed, these ahpC::Tn10 insertions lead to elevated expression from all peroxide regulon promoters, including those for mrgA, katA, hemAXCDBL, and ahpCF. As a result, the ahpC::Tn10 mutants display an increased resistance to H2O2. The ahpCF promoter region contains three sequences similar to the peroxide regulon consensus operator (per box). We demonstrate that the ability of ahpC::Tn10 mutations to derepress mrgA requires aerobic growth. In contrast, a second distinct trans-acting regulatory mutation bypasses this requirement for aerobic growth. Since the peroxide regulon is activated in the absence of AhpCF, which degrades alkyl hydroperoxides, we propose that organic hydroperoxides may be physiologically relevant inducers in vivo.
Links	PubMed PMC178545
Keywords	Aerobiosis; Amino Acid Sequence; Anaerobiosis; Arabidopsis Proteins; Bacillus subtilis/drug effects; Bacillus subtilis/enzymology; Bacillus subtilis/genetics; Bacillus subtilis/growth & development; Bacterial Proteins/biosynthesis; Bacterial Proteins/genetics; Base Sequence; DNA-Binding Proteins/biosynthesis; DNA-Binding Proteins/genetics; Gene Expression Regulation, Bacterial; Genes, Bacterial; Genes, Reporter; Hydrogen Peroxide/pharmacology; Molecular Sequence Data; Mutagenesis, Insertional; Mutation; Operon; Oxidoreductases/genetics; Peroxidases; Peroxiredoxins; Phenotype; Plant Proteins/genetics; Regulon; Repressor Proteins/genetics; Trans-Activators
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
BACSU:AHPC		GO:0006950: response to stress	ECO:0000315:		P		..a katA ahpC double mutant (HB6567 and its derivatives) exhibits slow growth in liquid media and lyses on LB plates. These defects are aggravated by the mrgA mutation in the triple mutant, HB6599. This strain could not grow aerobically (and grew only poorly microaerobically) in our defined minimal medium. Cell viability measurements with rich media confirm that katA ahpC (HB6567) and katA ahpC mrgA (HB6599)mutants are most compromised in aerobic growth, but these strains grow as well as the wild type microaerobically.	complete CACAO 2747

References

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