Organization of Lrp‐binding sites upstream of <i>ilvlH</i> in <i>Salmonella typhimurium</i>

Wang, Qing; Sacco, Margherita; Ricca, Ezio; Lago, C. T.; DeFelice, Maurilio; Calvo, Joseph M.

doi:10.1111/j.1365-2958.1993.tb01179.x

Cited by 34 publications

(27 citation statements)

References 17 publications

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“…Fig. 3B) (28,30), and a similar consensus was derived by Rex et al from a comparison of sequences of Lrp-related genes (21). Within the sequence shown in Fig.…”

Section: And C [Compare Fragments F-hb F-rb and F-hr])mentioning

confidence: 90%

“…A mutational analysis showed that the N-terminal third of Lrp is responsible for DNA binding, the middle third mediates transcriptional activation, and the C-terminal third determines the response of Lrp to leucine (19). In vitro, Lrp binds in a sequence-specific fashion to multiple sites upstream of the ilvIH promoters from E. coli and Salmonella typhimurium (28,30) and bends DNA upon binding (29). Binding of Lrp to these sites is both necessary and sufficient for transcriptional activation of the ilvIH operon (31).…”

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confidence: 99%

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Regulation of the Escherichia coli lrp gene

Wang

Friedberg

et al. 1994

J Bacteriol

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Lrp (leucine-responsive regulatory protein) is a major Escherichia coli regulatory protein which regulates expression of a number of operons, some negatively and some positively. Operons that are affected by the presence or absence of Lrp includefanABC (3), gcv (10), ginA (5), gltBD (5), ilvIH (20), livJ and livK (7), lysU (6, 11), ompC and ompF (5), oppABCDF (1), papBA (3), sdaA (12), serA (12, 21), and tdh (12, 21). Some of these operons (e.g., ilvIH) are known to be directly controlled by Lrp, whereas others (e.g., ginA) are affected only indirectly by Lrp. Other operons that are affected by Lrp were identified by a plac Mu mutational analysis and by two-dimensional gel electrophoresis (5, 10). Many operons under control of Lrp are also subject to control by leucine. A striking feature of the Lrp regulon is the variety of ways that leucine and Lrp interact to regulate gene expression (16). Of the operons activated by Lrp, in some cases the activation requires leucine, in some cases the activation is negated by leucine, and in other cases the activation is independent of leucine. Similarly, for operons which are negatively regulated by Lrp, the same three subcategories have been observed: leucine negates the effect, leucine is required for the effect, and leucine has no effect. The molecular mechanisms underlying these six different patterns of regulation involving Lrp and leucine are only partially understood.Lrp, a dimer containing two identical subunits of molecular mass 18.8 kDa, is present in E. coli at a level of about 3,000 molecules per cell (32). Its amino acid sequence is evolutionarily related to that of AsnC, a regulatory protein that controls

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“…Fig. 3B) (28,30), and a similar consensus was derived by Rex et al from a comparison of sequences of Lrp-related genes (21). Within the sequence shown in Fig.…”

Section: And C [Compare Fragments F-hb F-rb and F-hr])mentioning

confidence: 90%

mentioning

confidence: 99%

Regulation of the Escherichia coli lrp gene

Wang

Friedberg

et al. 1994

J Bacteriol

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“…If in fact each GACTN NNAGTC is bound by a C protein dimer, the center-to-center distance of 15 bp for the two sites means that the two dimers would occupy opposite faces of the double helix. This pattern of multiple binding sites, all with the same polarity, on two faces of the double helix is also seen with another transcriptional activator-the leucine-responsive regulatory protein (Lrp) of E. coli (56,62,64). Lrp, like the C proteins, is a small dimeric protein with a predicted helix-turn-helix motif that recognizes a symmetrical sequence with a central A/T triplet (21,51,56).…”

Section: Discussionmentioning

confidence: 99%

Role and Mechanism of Action of C · Pvu II, a Regulatory Protein Conserved among Restriction-Modification Systems

et al. 2000

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The PvuII restriction-modification system is a type II system, which means that its restriction endonuclease and modification methyltransferase are independently active proteins. The PvuII system is carried on a plasmid, and its movement into a new host cell is expected to be followed initially by expression of the methyltransferase gene alone so that the new host's DNA is protected before endonuclease activity appears. Previous studies have identified a regulatory gene (pvuIIC) between the divergently oriented genes for the restriction endonuclease (pvuIIR) and modification methyltransferase (pvuIIM), with pvuIIC in the same orientation as and partially overlapping pvuIIR. The product of pvuIIC, C ⅐ PvuII, was found to act in trans and to be required for expression of pvuIIR. In this study we demonstrate that premature expression of pvuIIC prevents establishment of the PvuII genes, consistent with the model that requiring C ⅐ PvuII for pvuIIR expression provides a timing delay essential for protection of the new host's DNA. We find that the opposing pvuIIC and pvuIIM transcripts overlap by over 60 nucleotides at their 5 ends, raising the possibility that their hybridization might play a regulatory role. We furthermore characterize the action of C ⅐ PvuII, demonstrating that it is a sequence-specific DNA-binding protein that binds to the pvuIIC promoter and stimulates transcription of both pvuIIC and pvuIIR into a polycistronic mRNA. The apparent location of C ⅐ PvuII binding, overlapping the ؊10 promoter hexamer and the pvuIICR transcriptional starting points, is highly unusual for transcriptional activators.The bacterial type II restriction-modification systems include a DNA modification methyltransferase (MTase) and a restriction endonuclease (REase), both of which act independently on the same DNA sequence (65). The REase cleaves duplex DNA sequences in the absence of sequence-specific DNA modification by the MTase. These systems can defend bacterial cells against viral infection, although other functional roles have also been proposed (45). Restriction-modification systems have provided an important focus for studies of molecular recognition. Biochemical and crystallographic analyses are yielding significant insights into the mechanisms of sequence recognition and catalytic activity of these proteins (3,18,50,66).

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“…Although the DNA sequence of the corresponding region in E. coli is different, the average A + T content is the same (Haughn et al 1986) and the promoter relay is conserved in both species . Another DNA binding protein, the leucine-responsive regulatory protein, Lrp, contributes by stimulating transcription of P ilvIH (Wang et al 1993) A gene may not have to leave its original host cell to experience new patterns of DNA topological influence. Simply repositioning the gene on the single, circular chromosome of the bacterium may achieve this effect (Brambilla and Sclavi 2015;Fitzgerald et al 2015;Gerganova et al 2015).…”

Section: Dna Supercoiling Bacterial Evolution and Pathogenesismentioning

confidence: 99%

DNA supercoiling is a fundamental regulatory principle in the control of bacterial gene expression

Dorman

2016

Biophys Rev

107

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Although it has become routine to consider DNA in terms of its role as a carrier of genetic information, it is also an important contributor to the control of gene expression. This regulatory principle arises from its structural properties. DNA is maintained in an underwound state in most bacterial cells and this has important implications both for DNA storage in the nucleoid and for the expression of genetic information. Underwinding of the DNA through reduction in its linking number potentially imparts energy to the duplex that is available to drive DNA transactions, such as transcription, replication and recombination. The topological state of DNA also influences its affinity for some DNA binding proteins, especially in DNA sequences that have a high A + T base content. The underwinding of DNA by the ATP-dependent topoisomerase DNA gyrase creates a continuum between metabolic flux, DNA topology and gene expression that underpins the global response of the genome to changes in the intracellular and external environments. These connections describe a fundamental and generalised mechanism affecting global gene expression that underlies the specific control of transcription operating through conventional transcription factors. This mechanism also provides a basal level of control for genes acquired by horizontal DNA transfer, assisting microbial evolution, including the evolution of pathogenic bacteria.

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Organization of Lrp‐binding sites upstream of ilvlH in Salmonella typhimurium

Cited by 34 publications

References 17 publications

Regulation of the Escherichia coli lrp gene

Regulation of the Escherichia coli lrp gene

Role and Mechanism of Action of C · Pvu II, a Regulatory Protein Conserved among Restriction-Modification Systems

DNA supercoiling is a fundamental regulatory principle in the control of bacterial gene expression

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