Induction of the alkylation-inducible aidB gene of Escherichia coli by cytoplasmic acidification and N-ethylmaleimide

Смирнова, Г. В.; Oktyabrsky, Oleg N.; Moshonkina, Elena V.; Zakirova, Natalia V.

doi:10.1016/0921-8777(94)90060-4

Cited by 16 publications

(10 citation statements)

References 28 publications

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“…Preincubation of cells with 25 mM acetate decreased the frequency of Trp ϩ revertants in cells surviving exposure to N-methyl-NЈ-nitro-N-nitosoguanidine (26). These workers have also suggested that the induction of the aidB locus, which is involved in some forms of DNA repair, is controlled both by NEM and by cytoplasmic pH (18,29). These data are consistent with a generalized effect of changes in pH i in protecting DNA against covalent modification.…”

Section: Discussionsupporting

confidence: 74%

Survival during exposure to the electrophilic reagent N-ethylmaleimide in Escherichia coli: role of KefB and KefC potassium channels

et al. 1997

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The role of the KefB and KefC potassium efflux systems in protecting Escherichia coli cells against the toxic effects of the electrophile N-ethylmaleimide has been investigated. Activation of KefB and KefC aids the survival of cells exposed to high concentrations (>100 M) of NEM. High potassium concentrations reduce the protection afforded by activation of KefB and KefC, but the possession of these systems is still important under these conditions. The Kdp system, which confers sensitivity to the electrophile methylglyoxal, did not affect the survival of cells exposed to NEM. Survival is correlated with the reduction of the cytoplasmic pH upon activation of the channels. In particular, the kinetics of the intracellular pH (pH i ) change are crucial to the retention of viability of cells exposed to NEM; slow acidification does not protect cells as effectively as rapid lowering of pH i . Cells treated with low levels of NEM (10 M) recover faster if they activate KefB and KefC, and this correlates with changes in pH i . The pH i does not significantly alter the rate of NEM metabolism. The possible mechanisms by which protection against the electrophile is mediated are discussed.The potassium pool of bacterial cells is subject to tight regulation through the activity of at least three uptake systems (TrkG/H, Kup, and Kdp) (2, 6, 9) and three or more efflux systems (4,20,22,23). However, the addition of electrophiles such as N-ethylmaleimide (NEM) to Escherichia coli cells elicits rapid potassium efflux that is reversible by the addition of reducing agents (3, 21). These effects of NEM arise from the specific, simultaneous activation of the KefB and KefC potassium efflux systems and the nonspecific inactivation of the major potassium uptake systems TrkG and TrkH (4,11,24). Methylglyoxal (MG) also activates the KefB and KefC systems but does so without altering the activity of the potassium uptake systems (14,15). Given the importance of the potassium pool for cells, deliberate perturbation of the pool must have a significant role in cell survival.The strong activators of the KefB and KefC systems are all electrophiles. The formation of glutathione metabolites is potentially the first step in detoxification of many toxic compounds, including electrophiles (19,25,30). Recent studies have shown that both KefB and KefC confer protection against the toxic effects of MG (13)(14)(15). MG is an endogenous electrophile synthesized under conditions of phosphate imbalance when cells are utilizing sugars or other compounds metabolized through the upper section of glycolysis (8). The KefB system is strongly activated by glutathione metabolites of MG and confers the greatest protection against this electrophile (13). The KefC system is only weakly activated by MG, although this is sufficient to confer moderate protection in mutants that lack KefB activity. The lesser role played by the KefC system in protection against endogenous electrophiles suggested that this system was primarily involved in protecting cells against externally...

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Section: Discussionsupporting

confidence: 74%

Survival during exposure to the electrophilic reagent N-ethylmaleimide in Escherichia coli: role of KefB and KefC potassium channels

et al. 1997

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“…The abrBl::TnlO-Kan mutation is presently poorly characterized because of strong selective pressure for second-site suppressor mutations which we call abrD. In this report we characterize the abrDl suppressor mutation and demonstrate that the abrDl mutation is responsible for the reduction in aidB expression normally seen in unaerated cultures, that abrD1 is also required for the low-pH-acetate induction of aidB recently demonstrated by Smirnova et al (30), and that abrDl is an allele of the rpoS gene. …”

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Induction of the Escherichia coli aidB gene under oxygen-limiting conditions requires a functional rpoS (katF) gene

et al. 1994

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The Escherichia coli aidB gene is regulated by two different mechanisms, an ada-dependent pathway triggered by methyl damage to DNA and an ada-independent pathway triggered when cells are grown without aeration. In this report we describe our search for mutations afecting the ada-independent aidB induction pathway. The mutant strain identified carries two mutations affecting aidB expression. These mutations are named abrB (aidB regulator) and abrD. The abrB mutation is presently poorly characterized because of instability of the phenotype it imparts. The second mutation, abrDl, reduces the expression of aidB observed when aeration is ceased and oxygen becomes limiting. Genetic and phenotypic analysis of the abrDI mutation demonstrates that it is an allele of rpoS. Thus, aidB is a member of the family of genes that are transcribed by a crs-directed RNA polymerase holoenzyme. Examination ofaidB expression in an rpoS insertion mutant strain indicates that both rpoSl3::TnlO and abrDl mutations reduce aidB expression under oxygen-limiting conditions that prevail in unaerated cultures, reduce aidB induction by acetate at a low pH, but have little or no elect on the adadependent alkylation induction of aidB.The Escherichia coli aidB gene is one of several genes induced in response to alkylation damage caused by treatments with agents that methylate DNA. The aidB gene encodes a protein that has a high degree of homology to several mammalian coenzyme A dehydrogenases (12). In agreement with this homology, it has been shown that the aidB gene product has isovaleryl coenzyme A dehydrogenase activity (12), an activity known to be required for leucine metabolism in mammalian cells (8,9). Overexpression of aidB protein has also been shown to reduce the mutagenic effects of the methylating agent N-methyl-N'-nitro-N-nitrosoguanidine, although the mechanism responsible for this resistance is unclear (12). Thus, aidB has roles in basic metabolism as well as defenses against methylation damage.In E. coli, the Ada protein mediates the response to alkylation damage, which has been called the adaptive response. Adaptive-response induction occurs when the Ada protein transfers a methyl group from methylphosphotriesters formed in DNA by methylating agents to its own Cys-69 residue (for reviews, see references 12, 15, and 36). Methylation of Ada converts this protein to a positive regulatory factor that binds sequences upstream of the ada, alkA, and aidB promoters, stimulating their transcription (12,15,36). Unlike the ada-alkB operon and the alkA gene, aidB is also subject to a second form of regulation (18,37,39). This second aidB induction pathway is activated when cells are grown in the absence of aeration and does not require a functional ada gene (37). Thus, there are two independent aidB regulatory pathways: an ada-dependent alkylation induction pathway and an ada-independent pathway induced when aeration is ceased and oxygen becomes limiting.To examine further the regulatory pathway triggered in unaerated cultures, random mini-T...

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“…aidB is induced by anaerobiosis or by addition of sodium acetate to growth medium, at a slightly acidic pH (ranging 6.0 to 6.8 [26]). This second pathway of expression is mediated by rpoS (30), a gene which encodes an alternative sigma factor of RNA polymerase, mainly active in late-logarithmic and stationary phases of E. coli growth (9,27).…”

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confidence: 99%

Structure and transcriptional regulation of the Escherichia coli adaptive response gene aidB

1994

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Expression of the Escherichia coli aidB gene is induced in vivo by alkylation damage in an ada-dependent pathway and by anaerobiosis or by acetate at pH 6.5 in an ada-independent fashion. In this report, we present data on aidB gene structure, function, and regulation. The aidB gene encodes a protein of ca. 60 kDa that is homologous to several mammalian acyl coenzyme A dehydrogenases. Accordingly, crude extracts from an aidB-overexpressing strain showed isovaleryl coenzyme A dehydrogenase activity. aidB overexpression also reduced N-methyl-N'-nitro-N-nitrosoguanidine-induced mutagenesis. Both ada- and acetate/pH-dependent induction of aidB are regulated at the transcriptional level, and the same transcriptional start point is used for both kinds of induction. Ada protein plays a direct role in aidB regulation: methylated Ada is able to bind to the aidB promoter region and to activate transcription from aidB in an in vitro transcription-translation system using crude E. coli extracts.

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Induction of the alkylation-inducible aidB gene of Escherichia coli by cytoplasmic acidification and N-ethylmaleimide

Cited by 16 publications

References 28 publications

Survival during exposure to the electrophilic reagent N-ethylmaleimide in Escherichia coli: role of KefB and KefC potassium channels

Survival during exposure to the electrophilic reagent N-ethylmaleimide in Escherichia coli: role of KefB and KefC potassium channels

Induction of the Escherichia coli aidB gene under oxygen-limiting conditions requires a functional rpoS (katF) gene

Structure and transcriptional regulation of the Escherichia coli adaptive response gene aidB

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