Comparison of the Sensitivities of Two
            <i>Escherichia coli</i>
            Genes to In Vivo Variation of Lrp Concentration

Chen, Changfeng; Newman, E. B.

doi:10.1128/jb.180.3.655-659.1998

Cited by 10 publications

(5 citation statements)

References 29 publications

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“…Regulatory extrapolation relies on a second tacit assumption: that levels of the conserved regulator are similar in the organisms being compared, and change similarly in response to growth conditions. Target gene regulation is, not surprisingly, affected by the level of the regulatory protein; this is specifically true for Lrp [ 66 , 92 , 116 ].…”

Section: Discussionmentioning

confidence: 99%

Limited functional conservation of a global regulator among related bacterial genera: Lrp in Escherichia, Proteus and Vibrio

et al. 2008

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Background: Bacterial genome sequences are being determined rapidly, but few species are physiologically well characterized. Predicting regulation from genome sequences usually involves extrapolation from better-studied bacteria, using the hypothesis that a conserved regulator, conserved target gene, and predicted regulator-binding site in the target promoter imply conserved regulation between the two species. However many compared organisms are ecologically and physiologically diverse, and the limits of extrapolation have not been well tested. In E. coli K-12 the leucine-responsive regulatory protein (Lrp) affects expression of ~400 genes. Proteus mirabilis and Vibrio cholerae have highly-conserved lrp orthologs (98% and 92% identity to E. coli lrp). The functional equivalence of Lrp from these related species was assessed.

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Section: Discussionmentioning

confidence: 99%

Limited functional conservation of a global regulator among related bacterial genera: Lrp in Escherichia, Proteus and Vibrio

et al. 2008

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“…In contrast, Gram-negative bacteria regulate metK expression through use of the metJ repressor protein in a complex with AdoMet as corepressor [130]. Expression of the metK gene of E. coli is also repressed by Lrp (leucine regulatory protein) [131].…”

Section: Mat In Bacteriamentioning

confidence: 99%

Methionine Adenosyltransferase (S‐Adenosylmethionine Synthetase)

Pajares

Markham

2011

Advances in Enzymology - And Related Areas of Molecular Biology

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10.3. Thermal Unfolding 10.4. Association of MAT III to form MAT I: Role of the Disulfide C35-C61 10.5. Complementary Folding Data Obtained in MAT Proteins of Different Origins 11. MAT Inhibitors 12. Role of MAT in Diseases 12.1. Cognitive and Neurodegenerative Diseases 12.2. Human Mutations in MAT1A Gene: Hypermethioninemia and Demyelination 12.3. MAT and Cancer 12.4. MAT and Ethanol 2. MAMMALIAN MATs Early studies on mammalian MATs showed the existence of this activity in all the tissues studied, the highest being observed in liver. However, complex kinetics were obtained which made the results difficult to interpret until the presence of several isoenzymes was realized. Separations carried out on phenyl Sepharose columns showed elution of three peaks with different hydrophobic character; these were named according to the order of elution as MAT I, II and III. All these isoenzymes share some characteristics such as the Mg 2+ dependence of their 9/14/2012 Page 6 of 80 activity (S 0.5 !1 mM), stimulation by K + ions, and their AdoMet-inducible tripolyphosphatase activity [4, 5]. 2.1. MAT I/III isoenzymes Since their discovery, these isoenzymes were known as liver-specific forms of MAT, until Lu et al. in 2003 [6] showed their presence also in pancreas. Several laboratories have reported in depth studies of MAT I and III which have been carried out using adult liver. The differences can be summarized as follows: i) MAT I is a tetramer whereas MAT III is a dimer, with respective Mr appearing as 200 and 110 kDa upon gel filtration chromatography, ii) their Km values for methionine are in the micromolar range for MAT I (60-120 µM) and in the millimolar range for MAT III (1 mM) [7, 8]; iii) MAT III can be activated by DMSO at physiological concentrations of methionine (60 µM) and is highly hydrophobic (eluting from phenyl Sepharose columns at 50% DMSO (v/v)); and, iv) AdoMet inhibits MAT I and activates MAT III. Some of these differences are normally used to distinguish between isoenzymes in activity assays. Both purified proteins show a common single band (designated "1) of approximately 48 kDa on SDS-PAGE, and antibodies raised against the dimer form recognized both, thus suggesting that a single type of subunit arranged in two assemblies could explain the presence of both oligomers [7]. Further experiments that supported this hypothesis included peptide mapping of the purified isoenzymes [7], dissociation of the tetramer to the dimer using LiBr [9] or N-ethylmaleimide (NEM) modification [10]. The final confirmation came upon cloning of a single cDNA [11, 12] followed by overexpresion in E. coli cells [13], which showed in vivo production of dimers and tetramers. This single subunit type is a product of the MAT1A gene that contains nine exons and eight introns spanning !20 kb [14], and has been localized by fluorescence in situ hybridization to the human chromosome 10q.22 [15]. Animal models, as well as the analysis of human samples, led to the identification of changes in the MAT I/III ratio in pathological conditi...

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“…Lrp does act as a regulator to some extent. When all transcription factors are present and only Lrp concen‐tration varies, expression from serA :: lacZ varies with Lrp concentration (Chen and Newman, 1998). Moreover, cellular Lrp concentration changes considerably in different media (Chen et al , 1997).…”

Section: Discussionmentioning

confidence: 99%

“…concentration (Chen and Newman, 1998). Moreover, cellular Lrp concentration changes considerably in different media (Chen et al, 1997).…”

Section: Binding Of Lrp To the Sera Promoter: Activation By Lrp At P1mentioning

confidence: 99%

“…Expression of both serA and serC is activated by the leucine‐responsive regulatory protein, Lrp, a global regulator first recognized as Rbl (regulation by leucine; Lin et al , 1990). Within a considerable range, the expression of serA is proportional to intracellular Lrp, as judged by the influence of arabinose via p ara BAD lrp (Chen and Newman, 1998). However, a basal level of expression is assured without Lrp.…”

Section: Introductionmentioning

confidence: 99%

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Structure of the Lrp‐regulated serA promoter of Escherichia coli K‐12

Yang

Lin

Newman³

2002

Molecular Microbiology

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SummaryExpression of the Escherichia coli serA gene is activated in vivo by the product of the lrp gene, leucineresponsive regulatory protein (Lrp), an effect partially reversed by L-leucine. We show here that serA is transcribed from two promoters, P1 45 bp upstream of the translation start site, and P2 92 bp further upstream. Lrp binds to a long AT-rich sequence from -158 to -82 from the start of the coding region, i.e. upstream of P1 and overlapping P2. It activates transcription from P1 and represses expression from P2. A second regulator, cAMP/CRP, activates P2, an effect that is largely inhibited by Lrp, such that catabolite repressor protein (Crp) and Lrp are rival activators of serA transcription.

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Comparison of the Sensitivities of Two Escherichia coli Genes to In Vivo Variation of Lrp Concentration

Cited by 10 publications

References 29 publications

Limited functional conservation of a global regulator among related bacterial genera: Lrp in Escherichia, Proteus and Vibrio

Limited functional conservation of a global regulator among related bacterial genera: Lrp in Escherichia, Proteus and Vibrio

Methionine Adenosyltransferase (S‐Adenosylmethionine Synthetase)

Structure of the Lrp‐regulated serA promoter of Escherichia coli K‐12

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