Methionine synthesis in Escherichia coli: effect of the MetR protein on metE and metH expression.

Cai, Xiaoyan; Maxon, Mary E.; Redfield, Betty; Glass, Robert E.; Brot, Nathan; Weissbach, Herbert

doi:10.1073/pnas.86.12.4407

Cited by 51 publications

(60 citation statements)

References 35 publications

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“…In E. coli the MetR protein activates expression of the metH and metE genes and probably metA, all of which are involved in methionine synthesis. Also, metR has been shown to downregulate its own transcription and to be repressed by MetJ (9,24). The methionine synthase genes metH (PA1843) and metE (PA1927) are present in P. aeruginosa and are 79% and 74% similar to their E. coli counterparts, respectively.…”

Section: Discussionmentioning

confidence: 99%

Swarming ofPseudomonas aeruginosaIs Controlled by a Broad Spectrum of Transcriptional Regulators, Including MetR

et al. 2009

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Pseudomonas aeruginosa exhibits swarming motility on semisolid surfaces (0.5 to 0.7% agar). Swarming is a more than just a form of locomotion and represents a complex adaptation resulting in changes in virulence gene expression and antibiotic resistance. In this study, we used a comprehensive P. aeruginosa PA14 transposon mutant library to investigate how the complex swarming adaptation process is regulated. A total of 233 P. aeruginosa PA14 transposon mutants were verified to have alterations in swarming motility. The swarmingassociated genes functioned not only in flagellar or type IV pilus biosynthesis but also in processes as diverse as transport, secretion, and metabolism. Thirty-three swarming-deficient and two hyperswarming mutants had transposon insertions in transcriptional regulator genes, including genes encoding two-component sensors and response regulators; 27 of these insertions were newly identified. Of the 25 regulatory mutants whose swarming motility was highly impaired (79 to 97%), only 1 (a PA1458 mutant) had a major defect in swimming, suggesting that this regulator might influence flagellar synthesis or function. Twitching motility, which requires type IV pili, was strongly affected in only two regulatory mutants (pilH and PA2571 mutants) and was moderately affected in three other mutants (algR, ntrB, and nosR mutants). Microarray analyses were performed to compare the gene expression profile of a swarming-deficient PA3587 mutant to that of the wild-type PA14 strain under swarming conditions. PA3587 showed 63% homology to metR, which encodes a regulator of methionine biosynthesis in Escherichia coli. The observed dysregulation in the metR mutant of nine different genes required for swarming motility provided a possible explanation for the swarming-deficient phenotype of this mutant.

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Section: Discussionmentioning

confidence: 99%

Swarming ofPseudomonas aeruginosaIs Controlled by a Broad Spectrum of Transcriptional Regulators, Including MetR

et al. 2009

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“…It appears that under the growth conditions tested in the present study the repressive effect of MetJ-SAM on metE transcription outweighs the inducing effect of MetR-Hcy. Indeed, an in vitro study of metE transcription has shown that MetR-Hcy fails to induce metE in the presence of MetJ-SAM (Cai et al, 1989).…”

Section: Discussionmentioning

confidence: 99%

Global effects of homocysteine on transcription in Escherichia coli: induction of the gene for the major cold-shock protein, CspA

et al. 2006

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Homocysteine (Hcy) is a thiol-containing amino acid that is considered to be medically important because it is linked to the development of several life-threatening diseases in humans, including cardiovascular disease and stroke. It inhibits the growth of Escherichia coli when supplied in the growth medium. Growth inhibition is believed to arise as a result of partial starvation for isoleucine, which occurs because Hcy perturbs the biosynthesis of this amino acid. This study attempted to further elucidate the inhibitory mode of action of Hcy by examining the impact of exogenously supplied Hcy on the transcriptome. Using gene macroarrays the transcript levels corresponding to 68 genes were found to be reproducibly altered in the presence of 0.5 mM Hcy. Of these genes, the biggest functional groups affected were those involved in translation (25 genes) and in amino acid metabolism (19 genes). Genes involved in protection against oxidative stress were repressed in Hcy-treated cells and this correlated with a decrease in catalase activity. The gene showing the strongest induction by Hcy was cspA, which encodes the major cold-shock protein CspA. RT-PCR and reporter fusion experiments confirmed that cspA was induced by Hcy. Induction of cspA by Hcy was not caused by nutritional upshift, a stimulus known to induce CspA expression, nor was it dependent on the presence of a functional CspA protein. The induction of cspA by Hcy was suppressed when isoleucine was included in the growth medium. These data suggest that the induction of CspA expression in the presence of Hcy occurs because of a limitation for isoleucine. The possibility that Hcy-induced cspA expression is triggered by translational stalling that occurs when the cells are limited for isoleucine is discussed.

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“…The metA gene, as well as all of the other methionine biosynthetic genes except metH, is negatively regulated by the MetJ repressor, with S-adenosylmethionine acting as a corepressor. In addition to MetJ-mediated repression, at least two genes, the metE and metH genes, are activated by MetR, a DNA-binding protein (4,28). Although homocysteine is required for the MetR-mediated activation of the metE gene, homocysteine plays an inhibitory role in the MetR-mediated activation of the metH gene (5,29).…”

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confidence: 99%

Regulation of the Salmonella typhimurium metA gene by the metR protein and homocysteine

1992

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The DNA sequence of the Salmonella typhimurium metA control region is presented. S1 nuclease mapping was used to determine the transcription initiation site. By measuring 0-galactosidase levels in Escherichia coli strains lysogenized with phage carrying a metA-lacZ gene fusion, the MetR protein was shown to activate the metA gene. Homocysteine, an intermediate in methionine biosynthesis, plays a negative role in the MetRmediated activation mechanism. Gel mobility shift assays and DNase I protection experiments showed that the MetR protein binds to a DNA fragment carrying the metA control region and protects a 26-bp region beginning 9 bp upstream of the -35 promoter sequence.

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Methionine synthesis in Escherichia coli: effect of the MetR protein on metE and metH expression.

Abstract: Studies

Cited by 51 publications

References 35 publications

Swarming ofPseudomonas aeruginosaIs Controlled by a Broad Spectrum of Transcriptional Regulators, Including MetR

Swarming ofPseudomonas aeruginosaIs Controlled by a Broad Spectrum of Transcriptional Regulators, Including MetR

Global effects of homocysteine on transcription in Escherichia coli: induction of the gene for the major cold-shock protein, CspA

Regulation of the Salmonella typhimurium metA gene by the metR protein and homocysteine

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