Integration host factor binds specifically to multiple sites in the ompB promoter of Escherichia coli and inhibits transcription

Tsui, Ping; Huang, Lin; Freundlich, Martin

doi:10.1128/jb.173.18.5800-5807.1991

Cited by 43 publications

(36 citation statements)

References 52 publications

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“…The initial experiments were done in cells containing an IHF mutation in order to increase the possibility of detecting ompB transcripts. Strains deficient in IHF have been shown to have increased ompB expression (49). The data in Fig.…”

Section: Resultsmentioning

confidence: 60%

“…During a study of binding of IHF to sites in the ompB promoter region (49), we noted a potential cyclic AMP-CRP binding site immediately upstream of the -35 region of the ompB promoter identified in vitro ( Fig. 1) (49). To investigate whether cyclic AMP-CRP influences ompB expression in vivo, we used strain JMS65, which has a chromosomal fusion between the promoter and first structural gene of ompB and lacZ.…”

Section: Resultsmentioning

confidence: 99%

“…In addition to osmoregulation, the expression of ompF and ompC is affected by a variety of other factors, including growth temperature (33), integration host factor (IHF) (27,44,48,49), stress conditions (6), and cyclic AMP (46). In many of these cases, it is not clear whether these conditions affect ompF and ompC directly or indirectly, through changes in the levels of OmpR and EnvZ (22).…”

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confidence: 99%

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Positive and negative control of ompB transcription in Escherichia coli by cyclic AMP and the cyclic AMP receptor protein

1992

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The ompB operon encodes OmpR and EnvZ, two proteins that are necessary for the expression and osmoregulation of the OmpF and OmpC porins in Escherchia coli. We have used in vitro and in vivo experiments to show that cyclic AMP and the cyclic AMP receptor protein (CRP) directly regulate ompB. ompB expression in an ompB-lacZ chromosomal fusion strain was increased two-to fivefold when cells were grown in medium containing poor carbon sources or with added cyclic AMP. In vivo primer extension analysis indicated that this control is complex and involves both positive and negative effects by cydic AMP-CRP on multiple ompB promoters. In vitro footprinting showed that cyclic AMP-CRP binds to a 34-bp site centered at -53 and at -75 in relation to the start sites of the major transcripts that are inhibited and activated, respectively, by this complex. Site-directed mutagenesis of the crp binding site provided evidence that this site is necessary for the in vivo regulation of ompB expression by cyclic AMP. Control of the ompB operon by cyclic AMP-CRP may account for the observed regulation of the formation of OmpF and OmpC by this complex (N. W. Scott and C. R. Harwood, FEMS Microbiol. Lett. 9:95-98, 1980).

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Section: Resultsmentioning

confidence: 60%

Section: Resultsmentioning

confidence: 99%

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confidence: 99%

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Positive and negative control of ompB transcription in Escherichia coli by cyclic AMP and the cyclic AMP receptor protein

1992

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“…The integration host factor and Fis proteins are known to be involved in regulation of a variety of genes in E. coli (40,46). We tested if these proteins affect fumA and fumC expression (Table 4).…”

Section: Resultsmentioning

confidence: 99%

Oxygen, iron, carbon, and superoxide control of the fumarase fumA and fumC genes of Escherichia coli: role of the arcA, fnr, and soxR gene products

1995

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The tricarboxylic acid cycle enzyme fumarase catalyzes the interconversion of fumarate to L-malate. Escherichia coli contains three biochemically distinct fumarases. While the fumA and fumB genes encode heat-labile, iron-containing fumarases, the fumC gene product is a heat-stable fumarase which does not require iron for activity. To study how the fumA and fumC genes are regulated, we constructed lacZ operon fusions to the fumA and/or fumC upstream regions. Expression of the fumA and fumC genes was lowest during anaerobic cell growth, in support of the proposed roles of FumA and FumC as aerobic fumarases. Transcription of the fumC gene was shown to be complex: it was dependent on both the fumA and fumC promoters. Anaerobic expression from the fumA promoter was derepressed in both an arcA and a fnr mutant, while expression from the fumC promoter was derepressed in only the arcA strain. The fumA promoter was also shown to be catabolite controlled, whereas the fumC promoter was relatively unaffected by the type of carbon used for cell growth. Cellular iron limitation stimulated fumC but not fumA expression. Superoxide radicals also caused increased fumC gene expression; fumA expression was unaffected. Both the superoxide control and the iron control of fumC expression required the SoxR regulatory protein. These studies suggest different physiological roles for the FumA and FumC fumarases. The iron-containing FumA fumarase is the more abundant enzyme under most conditions of aerobic cell growth except when iron is limiting; FumC, which lacks iron, appears to be a backup enzyme that is synthesized optimally only when iron is low or when superoxide radicals accumulate.

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“…Thus, OmpR levels are elevated in the parent strain grown in high-osmolarity medium and in the envZ473 and envZJl (10) strains. Although the regulation of the ompB operon has not been well studied, it has been suggested that integration host factor may play a role in modulating the steady-state levels of OmpR in the cell, which may, in turn, affect ompF and ompC regulation (30). Future studies on the regulation of ompB and the effect that elevated levels of OmpR have on porin gene expression should provide greater insight into the molecular mechanism by which ompF and ompC are regulated.…”

Section: Discussionmentioning

confidence: 99%

Molecular analysis of the signaling pathway between EnvZ and OmpR in Escherichia coli

Waukau

Forst

1992

J Bacteriol

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OmpR is a DNA-binding protein that regulates transcription of ompF and ompC. The activity of OmpR is controlled by the inner membrane osmosensor, EnvZ. In order to study the signaling process between EnvZ and OmpR, we analyzed two different envZ strains: the envZ473 strain, in which OmpC is constitutively produced and OmpF is fully repressed, and the envZ3 strain, in which the production of OmpC is greatly reduced and OmpF is not fully repressed by high-osmolarity growth conditions. Using direct sequencing of DNA derived from the polymerase chain reaction amplification method, we identified the mutation in the envZ473 strain as a Val-241-to-Gly substitution and the mutation in the envZ3 strain as an Ala-219-to-Val substitution. The relative DNA-binding affinity of OmpR derived from the envZ473 strain was dramatically increased for the upstream sequence of both ompF and ompC. In contrast, OmpR derived from the envZ3 strain was not converted to the high-affinity form. The intracellular levels of OmpR-phosphate, as analyzed by the in vivo phosphorylation approach, significantly increased in the envZ473 strain, while in the envZ3 strain the levels were considerably reduced, relative to those found in the parent strain. The intracellular level of OmpR protein in the envZ473 strain was also found to be markedly elevated relative to that of the parent strain. These results are discussed in relation to the role of phosphorylation and relative DNA-binding affinity of OmpR in the expression of ompF and ompC.

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Integration host factor binds specifically to multiple sites in the ompB promoter of Escherichia coli and inhibits transcription

Cited by 43 publications

References 52 publications

Positive and negative control of ompB transcription in Escherichia coli by cyclic AMP and the cyclic AMP receptor protein

Positive and negative control of ompB transcription in Escherichia coli by cyclic AMP and the cyclic AMP receptor protein

Oxygen, iron, carbon, and superoxide control of the fumarase fumA and fumC genes of Escherichia coli: role of the arcA, fnr, and soxR gene products

Molecular analysis of the signaling pathway between EnvZ and OmpR in Escherichia coli

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